• アイコナール



    空間におけるある波の位相が同一の面を光路長(位相を2πで割って波長をかけたもの)が同一の面に換算したもの。アイコナールSの一定の面は等位相面を表す。アイコナールの勾配∇Sは光線の進む方向を与える。|∇S |はその場所の屈折率を与える。アイコナールの考えは、屈折率の代わりに、結晶のひずみに応じてブロッホ波の振幅が場所的に変化していく様子を記述する動力学理論に使われている。

    "Eikonal" is defined as the line of constant optical path length of a wave, which is obtained by multiplying the line of constant phase by λ/2π,whereλis the wave length. The constant plane of eikonal S expresses the plane of the same phase of the wave. The gradient of eikonal, ∇S gives the traveling direction of the wave. |∇S | gives the refractive index at the corresponding position. The concept of eikonal, instead of the refractive index, has been applied to describe the local change of the amplitudes of Bloch waves in a distorted crystal.

  • アイソクロマティシティ



  • アインツェルレンズ

    einzel lens



    An electrostatic lens that has the same potential at the entrance and exit of the lens. Normally, the "einzel lens" consists of three electrodes. Two electrodes at both ends are set at the ground potential, and a positive or negative potential is given to the central electrode. The lens with a positive potential at the central electrode is called the acceleration-type einzel lens, whereas the lens with a negative potential is called the deceleration-type einzel lens. Both are convex lenses. The electrons passing through the einzel lens undergo lens action without acceleration and deceleration at the exit of the lens. This lens is used for ion-beam instruments, for example, an ion mass analyzer.

  • アクティブ磁場キャンセル装置

    active magnetic-field canceller



    An instrument that detects momentarily (ever) changing magnetic fields over a TEM and generates the anti-phase magnetic fields against the magnetic fields to cancel them.

  • アクロマティック面

    achromatic plane



    Let electron beams with different energies, which exit from one point on the object plane and pass through an energy filter, meet at one point on an image plane without energy dispersion. This image plane, on which chromatic aberration does not appear, is called the "achromatic plane." An image formed on the achromatic plane is called the achromatic image.

  • アナスティグマート




    A lens that corrects all of five Seidel aberrations. Almost all the commercial cameras, which have been recently developed, are fitted with an anastigmat lens.

  • アナプラート




    A lens that corrects spherical and coma aberrations. A telescope and an optical microscope are equipped with an achromatic (chromatic aberration corrected) "anaplat." The anaplat is accomplished in the following way. The surface at the object side of the lens is finished in a spherical shape to eliminate the spherical aberration. The surface at the image side of the lens is fabricated to suppress the occurrence of the coma aberration (surface satisfying the sine condition).

  • 油回転ポンプ

    (oil) rotary pump



    The (oil) rotary pump rotates a rotor in a case at the hermetic state maintained using oil to aspirate gas molecules into the inlet, and the gas molecules are compressed to open a valve at the outlet, then gasses are ejected to the air. Since the rotary pump operates from atmospheric pressure (105 Pa), the pump is used for rough pumping of a TEM and for evacuation of the back side of the (oil) diffusion pump and the turbo-molecular pump. The working pressure is 1055 to 1 Pa. If a long-time evacuation is continued at the evacuation limit, reflux of the oil vapor of the pump to the vacuum chamber occurs. Thus, the long-time evacuation by the pump should be avoided. When an oil-free pump is required, the scroll pump is used.

  • 油拡散ポンプ

    (oil) diffusion pump



    The (oil) diffusion pump heats the oil to a high temperature. The oil vapor is sprayed out at a high speed from the nozzle. The residual gas molecules are carried with the aid of the jet flow of the vapor. The back side of the pump is evacuated with a rotary pump. The pump mechanism is simple and its price is low. Since the diffusion pump operates from 10-1 Pa and its evacuation speed is high, the pump is used for evacuation of the TEM camera chamber with a large evacuation volume and large gas emission. The working pressure is from 10-1 to 10-8 Pa. When oil-free, high vacuum is required, the pump cannot be used. The pump is not suitable for pumping H2O.

  • 粗引き

    rough pumping



    "Rough pumping" means pumping from atmospheric pressure to the pressure for switching to the main high-vacuum pumping. In the rotary-diffusion pump system, the switching pressure is between 1 Pa and 0.1 Pa.


    ALCHEMI atom-location by channeling-enhanced microanalysis



    "Atom-location by channeling-enhanced microanalysis (ALCHEMI)" is a method that determines sites (locations) of impurity atoms in a crystal by utilizing a phenomenon where the incident electrons pass through specific atom sites (electron channeling). Sites occupied by impurity atoms can be distinguished from the intensity difference of characteristic X-rays (EDS spectra) observed at a small positive tilt angle and a small negative tilt angle from an exact Bragg condition, the tilt angle being adjusted by observing the electron diffraction pattern. In this method, EDS spectra are measured at two crystal orientations but recently, a more reliable technique has been prevailing. That is, a technique of two-dimensional rocking of the incident electron beam enables us to obtain patterns of characteristic X-ray intensities over a large angular range.

  • アルファフィルタ

    alfa filter



    One of the in-column type energy filters, which is installed between the intermediate and projector lenses in a TEM. The "alfa filter," whose principle of energy dispersion is the same as that of the omega filter, consists of two electromagnets instead of four electromagnets in the omega filter. Since the trajectory of electrons passing through the alfa filter takes the shape of a letter "alfa," this is called alfa filter. Its energy dispersion is ~0.7 μm/eV, which is smaller than that of the omega filter.

  • アルファフリンジ

    α fringe



    "α fringe" means a fringe contrast, which is observed in bright- and dark-field images under a two-beam approximation condition in the case where the upper and lower crystals are shifted to each other (for example, stacking faults) at an interface oblique to the surface of a crystalline specimen. The end fringes, which appear at the intersection between the interface and the upper and lower surfaces, exhibit symmetric contrast in the bright-field and anti-symmetric contrast in the dark-field with respect to the center of the fringe (specimen).

  • 暗視野像

    dark-field image



    An image that is produced by one diffracted wave in a diffraction pattern formed on the back focal plane of the objective lens, using the objective aperture. A location in the image, where the selected diffracted wave takes place, appears bright. The dark-field image, together with the bright-field image, is used for analysis of lattice defect and measurement of specimen thickness.

  • アンダーフォーカス




    "Underfocus" means that the excitation of the objective lens in a TEM is slightly decreased from that at the in-focus (focused on a specimen). At this excitation, the image produced on the selector aperture is the specimen image when the objective lens is focused on a position above the specimen. To enhance contrast in a bright (or dark) field image (to make the outline of the image clear), the image is often taken at a slight underfocus, instead of at the in-focus.

  • イオンエッチング

    ion etching



    "Ion etching" is a technique to selectively remove specific atoms and the atoms at lattice defects. This technique is used for observation of textures on a specimen surface. A technique of uniform and nonselective thinning for specimen preparation of TEM is ion milling. Sometimes, ion etching is confused with ion milling.

  • イオン化エネルギー

    ionization energy



    An energy required for removing one electron from an atom at the ground state to make a monovalent cation. It is called the first ionization energy.

  • イオン化断面積

    ionization cross section



    When a neutral atom or molecule loses or receives electrons by collision with other particles, the atom or molecule becomes an ion. This phenomenon is called ionization. "Ionization cross section" is the ionization probability expressed by dimension of area.

  • イオンクリーナ

    ion cleaner



    An ion cleaning tool that removes contaminants on a TEM specimen, which are residual substances deposited on a specimen at specimen pre-treatment, and contaminated substances deposited on a specimen in specimen storage. The specimen holder on which a specimen is set is inserted into an "ion cleaner." Then, a glow discharge due to residual gasses in the ion cleaner is generated and the ionized gasses by discharge irradiate the specimen. This chemical-reaction of the ionized gasses removes the contaminants (in particular, polymerized substances of hydrocarbons) deposited on the specimen.

  • イオンスパッタリング

    ion sputtering



    "Ion sputtering" is a phenomenon where atoms are sputtered from a solid surface when ionized and accelerated atoms or molecules hit the solid surface. This phenomenon is utilized for formation of a thin film on a solid surface, specimen coating and ion etching. In the case of specimen coating, discharge is generated in a low vacuum or in an Ar gas environment under a vacuum, the ionized gas is accelerated and hits a target material (Au, Pt, etc.) at the anode. Then, the material is emitted from the target surface and deposit on a specimen at the cathode, specimen being coated.

  • イオンポンプ(スパッタイオンポンプ)

    ion pump (sputter ion pump)



    A dry vacuum pump that does not use oil. In the sputter ion pump, residual gasses are ionized utilizing electric and magnetic fields. The produced ions strike a titanium cathode to sputter titanium atoms. Then, the sputtered titanium atoms form a fresh getter film (film subjected to chemical adsorption). As a result, active gasses (hydrogen, oxygen, carbon monoxide, etc.) are adsorbed to the getter film, and inert gasses (helium, etc.) are ionized and adsorbed to the cathode. The pump is used for evacuation of the electron gun chamber and the column of TEM, which require high vacuum. The working pressure is 10-4 to 10-9 Pa.

  • イオンミリング

    ion milling



    "Ion milling" is a specimen preparation technique that is used when electrolytic polishing or chemical polishing cannot be used to prepare a specimen. This technique is particularly effective for the specimen preparation when cross-section observations of layered materials are requested. A thin cross sectional film is prepared by milling surface layer atoms with the irradiation of an argon ion beam accelerated at 2 kV to 10 kV with a grazing incidence angle less than 10°. The disadvantage of ion milling is that damage to the specimen is unavoidable. Commercially-available ion-milling instruments are equipped with an optical microscope or a CCD camera with a magnification of several ten times to view the state of the specimen.

  • イオンめっき(イオンプレーティング)

    ion plating



    "Ion plating" is a technique to form a thin metal layer deposited on a surface of a solid by ionizing metal. In this technique, discharge is generated in a low vacuum or a gas environment between the substrate acting as a cathode and a metal evaporation source acting as an anode. Then, metal atoms are evaporated and ionized, and accelerated by an electric field, then finally form a thin layer on the substrate.

  • 異常吸収

    anomalous absorption



    When an incident electron beam travels a crystalline specimen, two kinds of electron waves are produced due to the dynamical diffraction effect. That is, one electron wave runs on atomic columns and the other electron wave runs between atomic columns. The former electron wave undergoes a larger absorption than the average absorption, whereas the latter electron wave undergoes a smaller absorption than the average absorption. This phenomenon is termed "anomalous absorption." The main cause of the anomalous absorption is thermal diffuse scattering of incident electrons.

  • 異常透過

    anomalous transmission



    When a crystalline specimen is thick, the electron wave that undergoes a larger absorption than the average absorption is damped rapidly; however the electron wave that undergoes a smaller absorption than the average absorption is damped slowly or has a greater transmissivity. This phenomenon is termed "anomalous transmission."

  • 位相コントラスト

    phase contrast



    phase contrast⇒
    加速電圧80 kVで取得された単層グラフェンの高分解能TEM像。

    Contrast produced by changes in phases of scattered waves. The HREM image is formed by the phase contrast. When a specimen is very thin, it is approximated that electron waves hardly suffer absorption but change only their phases (weak phase object approximation). If an aberration-free lens is used to cause interference between transmitted and scattered waves, no contrast appears on the ideal image plane. That is, the phase shift of the scattered waves does not cause the intensity variation in the image. The scattered waves undergo a phase shift of π/2 with respect to the transmitted wave. If the phase of the scattered waves is further shifted by π/2 in such a way that the amount of phase shift due to the spherical aberration of the electron lens is adjusted by the amount of defocus, the resultant phase shift of the diffracted waves becomes πwith respect to the transmitted wave. This phase change of the diffracted waves (π) is converted into the change of amplitude (not complex number but real number), producing contrast in the image due to the interference between the transmitted wave and diffracted waves. When an appropriate defocus amount is selected so that the phase of scattered waves is shifted by π/2 over the wavenumber range as wide as possible and the amplitudes of the waves become as large as possible, the structure image is obtained.

    位相コントラスト:phase contrast
    High-resolution TEM image of a single-layer graphene taken at an accelerating voltage of 80 kV.

    Since the graphene is regarded as a weak-phase object, the image contrast of the graphene reflects the phase change of electrons scattered by carbon atoms. This image is acquired using an electron microscope equipped with a Cs corrector at a slight defocus to create the phase contrast.
    Hexagonal grids of the graphene are seen in most parts. In the area enclosed by white dashed lines at the left, a lattice defect is seen. In the area enclosed by yellow dashed lines at the upper left, the graphene is seen to take an amorphous state.

  • 位相コントラスト伝達関数

    PCTF phase-contrast transfer function



    phase-contrast transfer function ⇒
    加速電圧200kVにおける位相コントラスト伝達関数の一例。 (a) 球面収差係数 0.5mm、(b) 球面収差係数 5umの場合。横軸は空間周波数、縦軸は試料の情報が電顕像にどのように伝達されるかを示す。この関数の値が負の場合は原子位置が黒く、正の場合は原子位置が白く結像される。位相コントラスト伝達関数を用いて像の解釈ができるのは、弱位相物体近似が成り立つような薄い試料の場合だけである。
    すべての空間周波数において位相コントラスト伝達関数の値は一定で、理想的には -1(あるいは+1)であることが望ましい。しかし、実際の透過電子顕微鏡の場合は球面収差等の収差があるため、位相コントラスト伝達関数の値はその絶対値が1より小さくしかも変動する。特に高周波数側では正負にまたがって大きく変動する。位相コントラスト伝達関数が初めて横軸を切る空間周波数(First Zero と呼ばれる)までのみ、コントラストの反転がなく試料の構造の情報が正しく伝達される 。球面収差が補正されていない(a)と補正されている(b)を比較すると、(b)の方が高い空間周波数まで関数が負の領域が大きく、試料の構造情報が正しく伝達されることが分かる。

    When electrons pass through the objective lens, spherical aberration of the objective lens causes the electron beam to undergo a displacement at the object plane, which is proportional to the cube of the incident angle to the objective lens. For an incident angle, this displacement can be canceled with an opposite displacement proportional to defocus of the objective lens. However, this cancelation is not accomplished for all the incident angles. The cancelation or compensation feature is described by the phase changes of the electron waves passing through the objective lens. That is, the phase changes are given as a function of the incident angle to the lens (or scattering angle from the specimen) and the defocus of the lens for a given Cs coefficient. This function is called “phase-contrast transfer function.”

    phase-contrast transfer function

    Example of the phase-contrast transfer function (PCTF) at an accelerating voltage of 200 kV for (a) Cs: 0.5 mm and for (b) Cs: 5 mm. The horizontal axis stands for spatial frequency and the vertical axis for the amount of information on the crystal structure of a specimen transferred to a TEM image. The negative region of PCTF contributes to form dark image for the atom sites and the positive region contributes to form bright image. It is noted that only the image of a very thin specimen, to which the weak phase object approximation can be applied, is interpreted using PCTF.
    It is desirable that the value of PCTF is constant (ideally –1 (or +1)) for all spatial frequencies. However, the real TEM accompanies aberrations such as spherical aberration, thus the absolute value of PCTF becomes less than 1 and is not constant. In particular at the high-frequency side, the value fluctuates greatly over the positive and negative values. The structural information on a specimen is transferred without contrast reversal till the frequency at which PCTF firstly crosses the horizontal axis (called First Zero). That is, the inverse of the frequency at First Zero means the resolution of the structural image. When PCTFs (a) without Cs correction and (b) with Cs correction are compared, it is clearly seen that the negative region of PCTF extends to a higher spatial frequency in (b). This indicates that the structural information on a specimen is much better transferred in the case of (b) with Cs correction.

  • 位相板

    phase plate



    phase plate ⇒

    (a) Zernike phase plate, (b) Hole-free phase plate
    ゼルニケ位相板は、透過波が通過する部分に穴があいており、透過波以外の散乱波を π/2だけ位相を変える。

    A plate that causes a change in the phase of an electron wave. The phase plate placed at the back focal plane of an electron microscope creates a relative phase change between the transmitted wave and scattered waves from a specimen. By the interference between the transmitted wave and the scattered waves, a phase change due to an object, which is originally difficult to view, can be visualized as an intensity change. Since the phase plate produces the relative phase change effectively at a small spatial-frequency region (corresponding to a long-distance region in the real space), it is effectively used in obtaining high contrast for biological specimen. There are two practically-used phase plates: Phase plate made of a carbon thin film with a controlled thickness having a hole at the center (Zernike phase plate) (Fig. (a)) and Hole-free phase plate (Fig. (b)).

    phase plate

    (a) Zernike phase plate, (b) Hole-free phase plate
    A Zernike phase plate has a hole where the transmitted wave passes and causes a phase shift of π/2 of scattered waves with respect to the transmitted wave.
    A hole-free phase plate does not have any hole, but produces a relative phase change between the transmitted wave and scattered waves. This phase change may be interpreted as follows: The part of the thin film plate which receives the electron beam is electrically charged and suffered by a change in electrostatic potential, and then the phase of the transmitted wave is changed relative to the scattered waves.

  • 一回散乱

    single scattering



    When the incident electrons that pass through a specimen are scattered only one time until these electrons exit from the specimen, this scattering phenomenon is termed "single scattering."

  • 異方性




    "Anisotropy" means that physical properties of a crystalline substance are different depending on its crystal orientations.

  • イマージョンレンズ

    immersion lens



    An electrostatic lens that has different potentials at the entrance and exit of the lens. The term of "immersion lens" originates from the immersion lens of light optical lenses, where the refraction index is different at the entrance and exit of the lens. The extraction electrode of the electron gun is an acceleration-type immersion lens. The Wien filter is normally a deceleration-type immersion lens. It is noted that lens action arises when electrons are accelerated or decelerated.

  • イメージEELS

    Image EELS



    "Image EELS" means a TEM image formed by the electrons of a specific energy selected from an EELS spectrum (electron energy-loss spectrum).

  • イメージウォブラ

    image wobbler



    A function to perform focusing of the illumination beam by the use of deflection coils below the condenser lens. The electron beam is repeatedly tilted at slightly positive and negative directions with respect to the optical axis. The excitation of the objective lens or the specimen position is adjusted so that the image does not move while the "image wobbler" is operated. The image wobbler is useful for rough focusing at magnifications up to ~50,000×.

  • イメージングプレート

    imaging plate


    X線、電子線、中性子線による電子励起で蛍光を発する現象を利用した積分型の二次元検出器。輝尽性発光体(BaFX:Eu2+ (X=Cl, Br, I))の微結晶をプラスチックフィルムに塗布したものである。感度の直線性が優れている。記録できる面積は約80mm × 100mmでダイナミックレンジ5~6桁と、両方とも大きい。露光されたイメージングプレートにHe-Neレーザを照射し、発光する青色光を光電子増倍管で電気信号に変えて記録された画像を読み出す。光電子増倍管1本では5桁のダイナミックレンジしかカバーできないので、最新の読み出し機では半導体検出器と組み合わせて6桁をカバーしている。イメージングプレートそのものが持っている大きなダイナミックレンジを有効に活用できるかどうかは、信号の読み出し機の性能に依存している。また位置分解能(画素サイズ)も読み出し機の性能によって15~50μmと変わる。階調は最大20ビット。大きな面積を必要とする低倍のTEM像や大きなダイナミックレンジを持つ回折図形の記録に有利である。CCDに比べると、オフライン利用に限定されるのが不利な点である。

    An integration-type two-dimensional detector that utilizes fluorescence emission generated by a beam of X-rays, electrons, or neutrons. The "imaging plate" is made of a plastic film coated with microcrystlas of photostimulable phosphor (BaFX:Eu2+ (X = Cl, Br, I)). The imaging plate has excellent linear sensitivity. The plate possesses a large recording area of about 80 mm × 100 mm and a large dynamic range of 5 to 6 digits. The exposed imaging plate is irradiated with He-Ne laser light, and then blue light emitted from the plate is converted into electric signals by a photomultiplier tube (PMT). By scanning the laser light on an imaging plate, a microscope image is obtained from the recorded signals. One PMT covers a dynamic range of only 5 digits but a recent reading device which combines a PMT and a semiconductor detector covers a 6-digit dynamic range. Whether a large dynamic range can be effectively used or not is dependent on the performance of a reading device. Also, the positional resolution (pixel size) changes from 15 μm to 50 μm depending on the performance of the reading device. The maximum gray level of the imaging plate is 20 bits. The imaging plate is advantageous for both recording a low-magnification TEM image that needs to cover a large area and a diffraction pattern that has a wide dynamic range. Compared to CCD, the disadvantage of the imaging plate is that its use is limited to offline.

  • 色収差

    chromatic aberration



    If there is energy (wavelength) spread of the incident electron beam or the electron beam passing through a specimen, the refraction angles of these electron beams are different depending on wavelength. Thus, a blurred image is produced on the image plane. This phenomenon is called "chromatic aberration." The energy spread of the electron beam arises from instability of the accelerating voltage, the spread of the initial speed of electrons emitted from the electron gun, the Boersch effect and change of the focal length caused by fluctuations of the excitation current of the lens coils. In addition, as a specimen is thicker (~10 nm or more), energy loss of electrons (change of wavelength) due to inelastic scattering gives rise to the chromatic aberration.

  • 色収差補正装置(Ccコレクター)

    Cc corrector



    The Cc corrector makes the chromatic aberration of the image-forming lens or the probe-forming lens to be 0 (zero) by producing a negative chromatic aberration. To produce the negative chromatic aberration, the corrector uses a quadrupole field formed by the superposition of an electrostatic field and a magnetostatic field. Multi-stage multi-poles are used to create the quadrupole field.
    The cylindrically symmetric convex lens of the magnetic field type or the electric filed type, which is used for electron microscopes, always possesses a positive chromatic aberration. Thus, electrons having a lower velocity are more largely deflected toward the convergence direction (inward).
    On the other hand, the quadrupole field of the Cc corrector exhibits a negative energy dispersion, which is opposite to that of the convex lens. Thus, the Cc corrector makes the electrons having a lower velocity to deflect more largely toward the divergence direction (outward). Therefore, incorporation of the Cc corrector into the convex lens system enables the positive chromatic aberration of the lens system to cancel with the negative chromatic aberration produced by the quadrupole field, making the chromatic aberration of the entire lens system of the electron microscope to be zero.

  • 陰極




    An electrode, to which a negative potential (voltage) is applied against the facing anode. The "cathode" means the filament of the thermionic-emission electron gun or the emitter (electron source) of the field-emission electron gun.

  • インコラムタイプ

    in-column type



    An energy filter or an energy analyzer that is installed in the column of a TEM is classified as "in-column type." This type includes an omega filter and an alfa filter.

  • インターバンドトランジション

    interband transition



    When the Bragg reflection is treated by the dynamical theory, dispersion surfaces (equi-energy surface), which give allowable wave numbers (equivalent energy planes) near Bragg reflections, are produced. Two dispersion surfaces are produced for each reflection. When the incidence direction of the electron beam onto a specimen crystal (the excitation error of the Bragg reflection) and the surface normal of the specimen are given, the allowed points on the dispersion surfaces are determined. As a result, the wave numbers and amplitudes of the allowed waves in the crystal are determined. If the crystal is perfect, these quantities are kept unchanged. If a defect, for example a stacking fault exists in the crystal, redistribution of the amplitudes occurs on the dispersion surfaces. Wave transfer to a different dispersion surface is called "interband transition." On the other hand, wave transfer within the same dispersion surface is called "intraband transition." The above interband transition in the case of a stacking fault takes place in the scope of elastic scattering. In the case of inelastic scattering, we can consider similar dispersion surfaces which are a little different in their energy from those of elastic scattering. Interband transition occurs at small-angle scattering of thermal diffuse scattering, but intraband transition occurs for plasmon scattering. In the case of core excitation, if interaction that gives rise to the core excitation is small (normally, small), intraband transition occurs. The electrons suffered by the intraband transition produce a similar image to the original image (without transition). However, since the symmetry of the Bloch wave of a dispersion surface is different from that of the other surface, the electrons suffered by interband transition do not form a similar image to the original image. (This term is different from "interband transition" used in solid state physics. In the case of the interband transition in solid state physics, the energy of the electron changes but it does not change in electron diffraction.)

  • イントラバンドトランジション

    intraband transition


  • インフォーメーションリミット

    information limit



    Information limit indicates the wave number at which phase information carried by the phase-contrast transfer function disappears. That is, it is determined as the wave number at which the envelope function reaches practically zero. The envelope function which gives damping of the phase contrast is determined by an energy spread of the electron beam and stability of the accelerating voltage (these two factors are related to chromatic aberration of the objective lens), stability of the objective lens and the divergence angle of the incident electron beam. The information limit is used as an indication of the resolution of a high resolution image. The resolution of the structure image is given by "first zero" of the phase-contrast transfer function in the ordinary sense. Phase information between the first zero and the information limit can be utilized to obtain a higher resolution of the structure image by computer-processing.

  • ウィンドウレス(窓材無し)型EDS検出器

    windowless EDS detector



    An EDS detector that does not use a window material for preventing contaminants onto its detector element. Since the windowless EDS detector suffers no X-ray absorption by the window material, the detector can analyze light elements such as beryllium (Be) and boron (B). Owing to a very high vacuum of the today’s microscope column and less severe deposition condition at Peltier cooling temperature than at liquid nitrogen temperature, the window material has become unnecessary. As a result, the windowless EDS detector has more been used in recent years.

  • ウィーンフィルタ

    Wien filter



    One of the in-column type energy filters. The "Wien filter" uses magnetic and electric fields perpendicular to each other for getting energy dispersion, though the omega filter and the alfa filter use only magnetic fields. The Wien filter is used as a monochromator by incorporating it in the illumination system of a TEM. Since its energy dispersion for a high-voltage 200 kV electron beam is small, the electron beam is introduced into the filter before the beam is accelerated or after the beam is decelerated to several 100 V. In this case, its energy dispersion is ~10 μm/eV. There is a limitation on applying a high voltage to the Wien filter due to discharge between electrodes. Thus, the filter is used for an incident electron beam at a voltage of ~10 keV or less. The advantage of the Wien filter is that the electron trajectory in the filter is parallel to the optical axis or forms a straight line.

  • ウィークビーム法

    weak-beam method



    The "weak-beam method" is a technique to take a dark-field image of a weakly excited reflection (for example, the 1st order reflection) at the exact Bragg setting of a high-order reflection (for example, the 3rd order reflection) under a systematic reflection condition. The observation of a dislocation by this method enables us to elucidate only a highly strained part of the dislocation with bright contrast against dark background. Thus, the dislocation is more sharply imaged and the dislocation position is more accurately determined. Accurate analysis of a narrowly extended dislocation can be performed.

  • ウェーネルト電極

    Wehnelt electrode



    A cylindrical electrode with a hole of a diameter of 1 to 2 mm, which is installed in the electron gun. By applying a bias voltage induced through a bias resistance, the "Wehnelt electrode" converges a diverging electron beam emitted from the electron gun.

  • ウルトラ・スィン・ウィンドウ型EDS検出器

    ultra-thin window (UTW) EDS detector



    An EDS detector that uses an organic thin film of 0.3 to 0.5 mm thickness as a window material to prevent contaminants onto a detector element.
    Aluminum is evaporated on the surface of the organic thin film so as to avoid charging on the window. Compared with the beryllium window EDS detector, the ultra-thin window (UTW) EDS detector better suppresses absorption of low energy X-rays. Thus, the detector can analyze elements lighter than sodium (Na).

  • ウルトラミクロトーム法




    A specimen preparation method that is used for thinning biological specimens, high-polymer specimens and composite materials. “Ultramicrotomy” is also used to prepare thin films of soft metals. The use of a diamond knife enables a specimen to be sequentially cut with a thickness of several 10 nm to 100 nm.

  • 運動学的回折

    kinematical diffraction


    結晶性の試料に入射した電子はブラッグ条件を満たす格子面で反射(回折)する。反射が試料中で1回しか起こらないと仮定して回折現象を扱う近似法をいう。反射の強度は結晶構造因子の二乗に比例する。この近似は試料が薄い場合になりたつ(おおざっぱにいって 3nm以下)。試料が厚くなると何回も反射が起きるので、この近似はなりたたなくなり、回折強度や電顕像の説明には動力学的回折理論を適用しなければならない。

    An electron that passes through a crystalline specimen is reflected (diffracted) by lattice planes satisfying a Bragg condition. The kinematical diffraction approximation assumes that the Bragg reflection occurs only one time in the specimen. In this context, the reflection intensity is proportional to the square of the crystal structure factor of the reflection. This approximation holds only when a specimen is thin enough (<3 nm). As a specimen is thicker, the reflection occurs many times. In this case, the dynamical diffraction theory must be applied to the interpretation of reflection intensities and electron microscope images.

  • エアリーディスク

    airy disk


  • 映進面

    glide plane



    A symmetry element of the crystallographic space group. When a crystal is mirrored with respect to a certain crystal plane (mirror plane) and successively translated parallel to this mirror plane by a length of 1/2 or 1/4 of the crystal unit-cell, the translated crystal can be equivalent to the original crystal. In this case, this plane is called "glide plane." The glide planes are denoted by g, instead of m in the case of mirror planes.

  • 衛星反射

    satellite reflection



    A modulation which has a longer period than that of the fundamental lattice takes place in certain crystals. In such cases, weak diffraction spots due to the modulation appear around the fundamental diffraction spots from the basic lattice. The weak diffraction spots are called "satellite reflections."

  • 液体金属イオン源

    liquid-metal ion source



    A "liquid-metal ion source" uses a metal that is at the liquid state at normal temperature. This ion source, normally liquid gallium, is used for an FIB instrument.

  • 液体窒素トラップ

    liquid-nitrogen trap



    A device to condense gas molecules onto a metallic surface exposed to vacuum by cooling the surface with liquid nitrogen. In a TEM, the "liquid-nitrogen trap" is utilized to maintain high vacuum in the microscope column to prevent contamination.

  • エスケープピーク

    escape peak



    In EDS analysis, when characteristic X-rays emitted from a specimen are detected with a semiconductor detector, part of the energies of the X-rays entering the detector is used to excite inner-shell electrons of silicon (Si) that is a constituent element of the detector. As a result, a small peak appears in an EDS spectrum at an energy lower than that of characteristic X-rays by the excitation energy of Si. This peak is called an "escape peak" and therefore, care must be taken for spectral analysis.

  • S字ひずみ

    S-shaped distortion



    "S-shaped distortion" means the distortion characteristic of the electromagnetic lens for the electron beam. Unlike the light beam in the optical lens, the electron beam suffers rotation in the electromagnetic lens. The rotation magnitude increases as the electron beam deviates from the optical axis, and then an image that should be observed as a line on the image plane (fluorescent screen) is viewed as an s-shaped image. The distortion becomes a problem for the projector lens because there exist electron beams which pass largely apart from the optical axis. Combination of lenses with opposite polarity can cancel the distortion, but this technique has not been used yet.

  • X線吸収分光

    XAS X-ray absorption spectroscopy



    A spectroscopy method to acquire a spectrum of X-rays absorbed by a substance. In a similar manner as EELS, XAS of the soft X-ray region enables us to obtain the density of states of the unoccupied state (conduction band) of a material.

  • X線発光分光

    XES X-ray emission spectroscopy



    A spectroscopy method, which measures the density of states of the occupied states (valence band) by analyzing X-rays emitted from a substance illuminated with an X-ray beam or an electron beam.

  • エッチング




    "Etching" is to selectively remove specific surface atoms of a specimen by utilizing chemical or physical reactions.

  • エネルギーコントラスト

    energy contrast



    Image contrast produced by differences in loss energies of inelastically scattered electrons. When the absorption-edge energy of a certain element is chosen with the energy-selection slit, mapping of the selected element in the specimen can be performed. In the future, it will be possible to perform electronic state mapping by selecting the excitation energy of a specific electronic states.

  • エネルギー選択スリット

    energy-selection slit



    The slit inserted into the energy dispersive plane of an energy filter, which selects electrons having specific energies.

  • エネルギー損失吸収端微細構造

    ELNES energy-loss near-edge structure



    A fine structure appearing in an energy region of about 30 eV above the absorption-edge energy in the EELS core-loss spectrum. This structure is called "energy-loss near-edge structure (ELNES)." The ELNES is produced by the transitions of electrons from the inner-shell state to the conduction band (unoccupied state), enabling us to obtain the density of states of the conduction band of a substance.

  • エネルギー幅

    energy spread



    "Energy spread" means an energy width of an electron beam. This is determined by fluctuations of the initial speed of electrons emitted from the cathode and by inelastic scattering of electrons in a specimen.

  • エネルギーフィルタ

    energy filter



    Instrument that selects electrons with only specific energies in electrons exiting from a specimen. When only elastically scattered electrons are selected by the energy filter, the background due to inelastically scattered electrons is successfully removed. Thus, a clear microscope image or diffraction pattern is obtained, which provides high-precision structural information. When the absorption-edge energy of a specific element is selected, the corresponding element is mapped. The energy filter is classified into the incolumn type incorporated in the TEM column and the post-column type attached below the column. There are various energy filters with different designs.

  • エネルギー分解能

    energy resolution



    "Energy resolution" is the minimum energy (eV) of a spectral peak that can be resolved in spectroscopy. In EDS, the detector performance determines the energy resolution to be 130 to 140 eV. In WDS, it is about 10 eV; however recently, some WDS analyzers can produce an energy resolution below 1 eV. In EELS, the energy spread of the incident electron beam almost determines the energy resolution. Standard EELS resolution using a field-emission electron gun is about 0.7 eV. When an electron gun is equipped with a monochromator, a higher energy resolution of about 0.2 eV is obtained.

  • エネルギー分光器

    energy analyzer



    An energy analyzer is used to disperse energies of characteristic X-rays or soft X-rays in WDS, and those of inelastically scattered electrons in EELS. In the case of WDS, analyzing crystals and gratings are respectively used for characteristic X-rays (element analysis) and for soft X-rays (measurements of the density of states of the valence band). In the case of EELS, an omega filter is used as an incolumn type energy analyzer, and a sector analyzer is used as a post-column type energy analyzer.

  • エネルギー分散型X線分光

    EDS energy-dispersive X-ray spectroscopy


    試料から発生した特性X線を直接半導体検出器で検出し、電気信号に変えて分光分析する手法。検出した特性X線のエネルギーに比例したパルス電流を生じさせ、これを多チャンネル波高分析器で選別して測定する。波長分散型と比べ軽い元素(B: ボロン以下)は分析できないが、X線の検出効率は高い。照射電流量は波長分散型より少なくてすむので(数pA~数nA)試料へのダメージは少ない。通常の分解能は~140eV(Mn: マンガンのKα発光(5.9keV)に対して)程度である。統計誤差で決まる分解能は発生X線のエネルギーEの平方根×√3程度である(生成される電子数nは、バンドギャップエネルギーを~3eVとして、n~E/3、統計誤差Δn~√n。したがって、エネルギー巾(誤差)~Δn・3=√E・√3)。最近はBe(ベリリウム)も分解できる検出器も開発されている。定量精度は0.5~5%である。EDSはEPMA(分光結晶を用いる)に比べて、空間分解能は2桁高いが分析の定量精度は1桁悪い。略称はEDSであるが、EDXともいう。

    Energy-dispersive X-ray spectroscopy (EDS) is an element analysis method. Characteristic X-rays generated from a specimen are detected by a semiconductor detector and converted into electric signals. In the EDS analyzer, the pulse currents that are proportional to the energies of the detected characteristic X-rays are generated, and then these currents are measured with a multi-channel pulse-height analyzer. EDS has higher detection efficiency of X-rays than WDS, but the analyzing power of light elements is lower than WDS. (EDS cannot analyze elements from boron (B) on down.) Since the illumination current of the electron beam for EDS can be decreased from several pA to several nA compared with WDS, the beam damage to a specimen is small. Normally, the resolution of EDS is ~140 eV for Mn Kα emission at 5.9 keV. The resolution determined by statistical counting error is around the square root of energy E of the generated X-ray × √3. (The number of created electrons n is obtained as n~E/3 by taking the band gap energy as ~3 eV. Since the statistical error Δn is ~√n, the energy spread (error) is obtained to be ~Δn・3 = √E・√3.) Recently, an EDS detector that can resolve a beryllium (Be) peak has been developed. Its quantification accuracy is 0.5 to 5%. Compared with EPMA that uses analyzing crystals, EDS provides high spatial resolution, 100 times better than EPMA but shows 10 times worse quantification accuracy than EPMA. "EDX" is also used as the abbreviation of energy-dispersive X-ray spectroscopy.

  • エピタキシ




    "Epitaxy" is a technique to deposit and grow a crystalline film on a crystalline substrate using vacuum evaporation (deposition) or chemical vapor deposition (CVD), etc. In epitaxy, the crystalline film formed has a specific orientation relation with the substrate crystal.

  • FFT

    FFT fast Fourier transform


    フーリエ変換を高速に行う計算方法。コンピューターを使うので連続的な積分の代わりに有限の離散的な和で実行される。離散的な和をいくつかのグループに分け、さらに計算の順序を工夫して計算量を大幅に減少させる方法。周期 N の離散フーリエ変換では、通常の変換では演算の回数がNの2乗に比例するが、FFTでは NlogN に比例する。高分解能像の解析等に使われる。

    A computing method to decrease the calculation time of a Fourier transform. Since "fast Fourier transform (FFT)" is executed using a computer, calculations are performed by a discrete finite sum, instead by an integration. It greatly decreases the computation time by dividing the calculation into certain sub-groups and by changing the order of the calculation. In a discrete Fourier transform with a period of N, the number of operation is normally proportional to N2 but it is decreased to N log N in FFT. This method is used for analysis of high-resolution images.

  • (L2, L3), (M4, M5)…スペクトル

    (L2, L3), (M4, M5)…spectra


    EELSスペクトルにおいて、50eV以上の領域に現れる元素固有の吸収端。吸収端は内殻電子の伝導電子帯への励起によって生じる。励起する内殻の違いによって、K、L、M...殻励起スペクトルと呼ばれる。内殻電子準位は、スピン軌道相互作用により、さらに細かく別れており、それらはK(1s1/2), L1 (2s1/2), L2(2p1/2), L3(2p3/2), M1(3s1/2), M2(3p1/2), M3(3p3/2), M4(3d3/2), M5(3d5/2), …と表される。3d遷移金属元素のL2と L3準位のエネルギー差は5~20eV程度なので、EELSスペクトルには、それらのエネルギー差だけ異なる、似た形状のスペクトルが連続して現れる。SiやAlではL2とL3準位の差が1eV以下と小さいために、分離しない一つの吸収端スペクトルとして観測されるので、L2,3とかかれることが多い。L2スペクトルとL3スペクトルの強度比は、内殻電子準位での電子の占有比からは1:2になると期待されるが、伝導電子帯の形状やコアーホール相互作用などによって強度比は1:2からずれる。4d遷移金属元素のM殻励起の場合には、M4およびM5スペクトルが2~10eV隔たって現れる。

    Absorption edges characteristic of elements, which appear in an energy region higher than 50 eV in an EELS spectrum. These absorption edges arise due to excitations of inner shell electrons to the conduction band. They are called "K, L, M…" shell excitation spectra depending on the excited inner shell. The inner-shell levels have fine structures due to the spin orbit coupling. The split levels are expressed as K(1s1/2), L1(2s1/2), L2(2p1/2), L3(2p3/2), M1(3s1/2), M2(3p1/2), M3(3p3/2), M4(3d3/2), M5(3d5/2), …. Since the difference of the L2 & L3 energy levels of 3d transition metals is 5 to 20 eV, two spectra with similar shape successively appear with the energy difference in the EELS spectrum. For Si and Al, the L2 & L3 spectra form a non-separated absorption-edge spectrum because the energy separation of the L2 & L3 levels is 1 eV or less. Thus, they are denoted as L2,3. The intensity ratio of the L2 & L3 spectra is expected to be 1:2 from the occupation ratio of the levels. However, the ratio experimentally observed is different from the ratio expected due to non-flat configuration of the conduction band and the core-hole interaction. In the case of the excitation of M shell electrons of 4d transition metals, M4 and M5 spectra appear successively with an energy difference of 2 to 10 eV.

  • エワルド球

    Ewald sphere



    Ewald sphere⇒
    金(Au)の[001]入射での逆格子点列 (格子面間隔d=0.204nm) とエワルド球。小さい円はMoKα特性X線 (λ=0.07109nm)、大きい円(円弧)は加速電圧200kVの電子線 (λ=0.002508nm) に対するエワルド球である。電子顕微鏡の取込角の一般的な限界である±10°まで表示してある。青色の逆格子点はブラッグ条件を近似的に満たす。

    The Ewald sphere is a sphere of the radius defined as the reciprocal of the wavelength of the incident wave 1/λ, and is drawn with the point as the center, the point being at the length 1/λ from a certain reciprocal lattice point along the direction of the incident wave to a specimen crystal. The Ewald sphere explains what Bragg reflections occur using the relation between the incident wave vector and the reciprocal lattice points. All of the reciprocal lattice points on the Ewald sphere satisfy the Bragg condition. For a high energy incident electron (100 or 200 keV), the Ewald sphere can be approximated as a flat plane because the radius of the Ewald sphere is much larger than the distance between the reciprocal lattice points. As a result, the reflections, which appear as cross sections between the Ewald sphere and the reciprocal lattice points, can be indexed easier than the indexing in X-ray diffraction.

    Ewald sphere

    The reciprocal lattice points of gold (Au) for [001] incidence (lattice spacing d = 0.204 nm) and the Ewald spheres. The small sphere is the Ewald sphere for X-ray of MoKa (λ = 0.07109 nm) and the large sphere (arc) is the Ewald sphere for an electron beam of 200 kV (λ = 0.002508 nm).
    The Ewald sphere for the electron beam is displayed up to ±10°, which corresponds to a usual limitation of the acceptance angle of an electron microscope. Blue reciprocal lattice points approximately satisfy the Bragg condition.

  • エンベロープ(包絡)関数

    envelope function



    envelope function⇒
    加速電圧200kVにおけるエンベロープ関数(包絡関数)の例 (黒線)。横軸は空間周波数、縦軸は試料の情報が電顕像にどのように伝達されるかを示す。包絡関数の値が1(あるいは-1)に近いほど、試料の構造の情報が結像に多く寄与する。包絡関数が零に近づくにつれて試料の構造情報は欠落してゆく。
    包絡関数は色収差や照射角広がり等の影響によって決まる干渉性の度合いを表す。色収差や照射角広がりが大きい場合は、散乱波の干渉性は空間周波数の増加とともに早く劣化し、包絡関数は早く零に近づく。実際の位相コントラスト伝達関数は、 灰色線で示すように包絡関数が掛かったもので、空間周波数の増加とともに像強度への散乱波の寄与が減少する。

    The phase-contrast transfer function plays an important role for the resolution of an HREM image contrast. Another important factor is the envelope function. The phase contrast is damped with increase of scattering angle due to chromatic aberration of the objective lens caused by energy difference in the electron beam, the divergence angle of the electron beam, stability of the objective lens, etc. The function that expresses the damping is called "envelope function." The spatial frequency at which the envelope function becomes practically 0 (zero) is called "information limit."


    Example of an envelope function (black line) at an accelerating voltage of 200 kV. The horizontal axis stands for the spatial frequency and the amount of information on the crystal structure of a specimen transferred to a TEM image. The closer the value of the envelope function to 1 (or –1), the more structural information on the specimen contributes to form a TEM image. The closer the envelope function to 0 (zero), the more structural information is lost.
    The envelope function expresses the degree of coherence of the scattered waves, which is determined by chromatic aberration, angular spread of an incident electron beam, etc. When the chromatic aberration or angular spread is large, the degree of coherence of scattered waves deteriorates quickly with increase of spatial frequency, or the envelope function attenuates quickly to 0. The phase-contrast transfer function (PCTF) should incorporate the effect of the envelope function, then resulting to an actual PCTF as indicated by a gray line. This PCTF shows that the contribution of the scattered waves to the image formation damps with the spatial frequency.


  • ADF(エーディーエフ)検出器

    annular dark-field detector



    An annular detector with an inner diameter of ~3 mm and an outer diameter of ~8 mm, which is used for obtaining a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image. The "annular dark-field (ADF) detector" of a phosphor screen or a YAG scintillator receives scattered electrons and converts them into a light signal. The light signal is directed to a PMT through a light pipe and converted into an electric signal, and the electric signal is amplified.

  • 凹面回折格子

    concave grating



    A kind of reflection grating that is designed in such a way that many grooves are cut in parallel on the surface of a spherical or parabolic concave mirror. The concave grating is used for not only spectroscopy but also for focusing a beam or producing a parallel beam.

  • オブジェクティブ ミニレンズ

    objective mini lens


    対物レンズの下におかれる弱いレンズ。対物レンズのように磁場を強めるポールピースを持たない。Low MAGモードで低倍率(~50~3000倍)を得るとき、対物レンズの励磁を切ってオブジェクティブ ミニレンズで制限視野絞り上に結像するために使われる。倍率は1~2倍。もう一つの使い方は、MAGモードで1000倍程度の低倍率を得るとき、対物レンズの性能(像質)を下げないために強励磁にしておき、オブジェクティブ ミニレンズを使って像を縮小(~0.5倍)し、広い視野を中間レンズに導くために使われる。

    The "objective mini lens" is a weakly excited lens placed below the objective lens. This lens does not have a polepiece to strengthen a magnetic field as the objective lens does. This lens is used to form an image on the selector aperture in Low MAG mode (~50× to 3,000×) by stopping the excitation of the objective lens. The magnification at the objective mini lens is 1× to 2×. This lens is also used to obtain a high quality low magnification image of about 1,000× in the MAG mode. That is, the excitation of the objective lens is kept strong to maintain image quality of the objective-lens, and the image is demagnified (to ~0.5×) by the objective mini lens, thus a wide view image is formed on the object plane of the intermediate lens.

  • オメガフィルタ

    omega filter



    omega filter ⇒
    エネルギーEの電子の軌道(光軸を通る軌道)を青で示し、⊿Eだけエネルギーを失った電子の軌道(エネルギー分散を起こした軌道)を赤線で示す。エネルギー分散が起きている面 (S) をスクリーンに投影すると、ロス(損失)エネルギーに対する強度分布(エネルギースペクトル)が観察される。面S上にはエネルギースリットが置かれている。
    また、エネルギー分散が消滅する面、すなわちアクロマティック面 (A) をスクリーンに投影すると、エネルギー分散の無い像が観察される。その際、エネルギースリットを用いて、ゼロロスエネルギーを選択するとゼロロス像(フィルタ像とも言う)が得られ、ロスエネルギーを選択するとロス像が得られる。

    (a) Siのエネルギースペクトル(加速電圧:200kV)、(b)エネルギースペクトルのラインプロファイル ⇒
    ZLPはゼロロスピーク。P1 はプラズモンロス (Ep = 16.7eV) によるピーク。P2, P3… はプラズモンの多重散乱によるピーク。L2,3 は内殻電子励起によるなだらかなピーク。

    cubic-BN [110]のCBED図形(加速電圧100kV) ⇒
    エネルギースリット無し (Unfiltered)の左図では、縞模様がぼやけて不明瞭であるが、エネルギースリットでロスエネルギー (約10eV以上) をカットした右図 (Filtered) では、縞模様が明瞭に観察されている。回折図形の定量解析を行う場合、エネルギーフィルタは必要不可欠である。

    氷包埋したリポソームの像(加速電圧200kV) ⇒

    One of the in-column type energy filters, which is installed between the intermediate and projector lenses in a TEM. The filter (spectrometer) is composed of four electromagnets and has a shape of the letter “omega.” Thus, this is called “omega filter.” Its energy dispersion is approximately 1 μm/eV for a 200 kV electron beam. The omega filter is used to date to acquire filtered (zero-loss) images, energy-loss images and zero-loss CBED patterns.


    Schematic of the action of the omega filter and an acquired spectrum.
    A blue curve shows the trajectory of electrons passing through the optical axis with an energy E. A red curve shows the trajectory of electrons suffered by energy dispersion with an energy loss of ⊿E. When the optical plane at which energy dispersion (S) is created is projected onto the screen, the intensity distribution against energy losses, or an energy spectrum is observed.
    When the achromatic plane (A), at which energy dispersion disappears, is projected onto the screen, an image without energy dispersion is observed. In this case, if the energy slit placed on plane S is inserted to pass no energy-loss electrons, a zero-loss image (so called “filtered image”) is acquired. If the energy slit selects energy-loss electrons, an energy-loss image is obtained.


    (a) Energy spectrum of Si acquired at an accelerating voltage of 200 kV. (b) Line profile of the energy spectrum. ZLP is the zero-loss peak. P1 is a peak of a plasmon loss electrons (Ep = 16.7 eV). P2, P3… are peaks produced by multiple scattering of the plasmon. Weak and broad peaks L2,3 are the spectra due to excitation of inner-shell electrons.

    cubic-BN [110]のCBED図形(加速電圧100kV)

    CBED patterns of cubic-BN [110] acquired at an accelerating voltage of 100 kV. The two patterns were taken by projecting the CBED patterns formed at the achromatic plane onto the screen. (a) CBED pattern without using the energy slit (unfiltered pattern). (b) Filtered CBED pattern by selecting zero-loss energy with the energy slit. The graphs below the patterns are line profiles of each line A-B.
    In the unfiltered pattern at the left, the patterns inside the CBED disks are unclear. To the contrary in the filtered pattern at the right, where the lost energies approximately more than 10 eV are cut, the patterns in the disks are clearly seen. The energy filter is indispensable for quantitative analysis of CBED patterns.


    TEM images of ice-embedded liposome acquired at an accelerating voltage of 200 kV, taken by projecting the images formed at the achromatic plane onto the screen. (a) Conventional image without using the energy filter (unfiltered image). (b) Zero-loss image using the energy filter (filtered image).
    It is seen that the image contrast of liposome is enhanced in the filtered image (b).

  • オンサイト励起

    on-site excitation



    In EELS, "on-site excitation" means that the inner-shell excitation occurs spatially only on an excited atom. When excitation of an inner-shell electron to an unoccupied state (band) is considered, since the wavefunction of the inner-shell electron is localized on an atom, if the final state is not overlapped with that wavefunction, the excitation (transition) does not occur. Thus, the ELNES spectrum reveals the anti-bonding state of the excited atom.

  • オージェ電子

    Auger electron



    When an atom at an excitation state makes a transition to the ground state, if its energy is not used to emit characteristic X-rays but used to emit an electron in the atom, the emitted electron is called "Auger electron." The Auger electron energy is characteristic of an element and the escape depth of the Auger electron is very small (0.5 nm to several nm). Thus, the Auger electron is utilized for qualitative and quantitative compositional analysis and electronic structure analysis (analysis of chemical-bonding states) on top surfaces of solids. The accuracy of Auger electron spectroscopy is about 10%.

  • オーバーフォーカス




    "Overfocus" means that the excitation of the objective lens in a TEM is slightly increased from that at the in-focus (focused on a specimen). At this excitation, the image produced on the selector aperture is the specimen image when the objective lens is focused below the specimen.

  • 加圧凍結法

    high pressure freezing


    急速凍結固定法の一種で、生体の組織や細胞、細菌などの試料を固定する方法である。試料を凍結する際に2,000気圧程度の圧力をかけることで、水の融点が下がり(2,000気圧で-20 ℃程度) 粘性が上がるため、組織の破壊の原因となる氷晶の形成が抑えられる。大気圧下での凍結に比べ、数十倍の深度(200 μm程度)で一様な非晶質氷の凍結を行うことができる。凍結後の試料を電顕観察する際には、(1)そのまま凍結切片を作製する場合や、(2)凍結置換法を行った後に試料を室温まで戻し、樹脂包埋後、超薄切片を作製する場合や、(3)凍結割断法によりレプリカを作製する場合がある。

    High pressure freezing, one of rapid freeze fixation techniques, is to fix biological specimens such as biological tissues, biological cells and bacteria.  Rapid freezing under an about 2000 atm suppresses formation of ice crystals, which give rise to the destruction of the tissues, by decreasing the melting point of water by about -20 °C and increasing its viscosity.  This technique provides a uniform freezing under amorphous ice with a depth more than one order of magnitude larger (about 200 μm) compared with the freezing depth at the atmospheric pressure.  Specimen preparation for TEM observation of the frozen specimen is carried out by one of the following three procedures.  (1) Applying freeze sectioning to the specimen, (2) Applying resin embedding and ultrathin sectioning to the specimen after the specimen is subject to freeze substitution and is returned to room temperature, and (3) Making a replica of the specimen by freeze fracturing.

  • 介在物




    Inclusions are impurity particles captured in a solid.

  • 回折限界

    diffraction limit


    光学系に収差が無い場合の集光限界。電子波には回折現象があるので、収差がない光学系においても、物体の一点から出射した電子波は像面で無限小の一点には集まらず、有限の大きさ(エアリーディスク)までにしか集光できない。回折収差によるエアリーディスクの半径 rはr=0.6λ/sinαである。ここで、λは電子線の波長、αはレンズの開き角である。この式から、エアリーディスクの大きさは電子線の開き角を大きくとると小さくなることがわかる。透過型電子顕微鏡で実現できている開き角は10-2radである。この集光限界のために理想レンズでも点分解能は無限に小さくはならない。

    The diffraction limit is the resolution limit due to diffraction of an electron wave for the optical system with no aberrations. Even in the aberration-free optical system, electron waves exiting from one point on the object do not form an infinitesimal point on the image plane but these electron waves are focused into a finite size spot (airy disk) due to their diffraction phenomenon. The radius r of the airy disk is given by the equation r = 0.6λ/sinα, whereλis the wavelength of the electron and α is the divergence angle of the electron. From the equation, it is seen that the size of the airy disk is small for a large divergence angle of the electron beam. In real TEMs, the achievable divergence angle is ~5×10-2 rad. This limitation makes it impossible to produce an infinitesimal point resolution even for ideal lenses.

  • 回折格子




    The grating is an element to obtain a spectrum utilizing diffraction. It is made of a metal and many equally spaced grooves are cut on the surface. (The minimum spacing between the grooves that can be cut is ~0.5 μm.) The spacing must be suitable for the wavelength of the spectrum to be measured. In order to obtain a spectrum from a wide energy range, several gratings with different groove spacings are required. Some gratings are designed to be cut with a non-equal pitch of grooves to reduce aberrations. The grating is used for electronic structure analysis by soft X-ray spectroscopy.

  • 回折コントラスト

    diffraction contrast


    TEM像における散乱コントラストの内、結晶性試料の場合、角度に関して連続的に分布している散乱波は、ブラッグ反射を起こして非連続的に分布する回折波となる。試料の場所 (位置) によって回折条件が変わると回折波の強さが変化して、像にコントラストがつくことを回折コントラストという。明視野像(透過波で結像される像)では、回折を起こした試料の部分は強度が減り暗く写る。暗視野像(一つの回折波で結像される像)では、その回折が起きている試料部分が明るく写る。

    diffraction contrast ⇒
    加速電圧200 kVで取得した多結晶Si(半導体配線)のTEM像と回折図形。

    (a) 明視野TEM像。大きさ数10 nm~数100 nmの多数の結晶粒で構成され、それぞれが異なる結晶方位をとっている。赤もしくは緑色矢印で示した結晶粒では、回折した波が対物絞りによって遮られるため、暗く観察されている。

    (b) (a)と同視野から得た暗視野TEM像。(a)の緑色矢印で示した結晶粒からの回折波を取り込むように対物絞りを挿入しているため、その部分が明るく観察されている。

    (c) 回折図形。多結晶からの回折図形のため、デバイ・シェラー環が観察されている。(a)、(b)の緑色矢印で示した結晶粒からの回折波を緑色丸で囲っている。

    Scattered electrons in a crystalline specimen are not continuously distributed with scattering angles but discontinuously distributed as diffracted waves. Diffraction contrast means the intensity change in an electron microscope image that is formed when the diffraction condition is changed with areas of the specimen. In the bright-field image (formed by the transmitted wave), the area where diffraction takes place loses its image intensity, thus getting dark. In the dark-field image (formed by a diffracted wave), the corresponding area gains image intensity, thus getting bright.

    回折コントラスト:diffraction contrast
    TEM images and a diffraction pattern of polycrystalline Si (a semiconductor interconnect) taken at an accelerating voltage of 200 kV.

    (a) Bright-field TEM image. The specimen is composed of many crystalline particles with size of a few 10 nm to a few 100 nm, which exhibit different crystal orientations. In the crystalline particles indicated by red allows and a green arrow, the diffracted waves are intercepted by the objective aperture. As a result, the particles are observed with dark contrast.

    (b) Dark-field TEM image taken from the same area in (a). The objective aperture is inserted so that the diffracted wave from the crystalline particles indicated by the green arrow in (a) is acquired. As a result, the particle is observed with bright contrast.

    (c) Diffraction pattern. Since the specimen is polycrystalline, the Debye-Scherrer ring is observed. A green circle encloses the diffracted wave from the crystalline particle indicated by the green arrow in (a) and (b).

  • 回折波

    diffracted wave



    A wave that undergoes Bragg reflection (diffraction) in a crystalline specimen. In the two-beam dynamical theory, the intensity of the diffracted wave periodically changes with specimen thickness.

  • 回転軸

    rotation axis


    結晶点群の対称要素の一つ。ある直線を軸として、結晶全体を一定の角度(180°, 120°, 90°, 60°)、回転させたとき、回転前の結晶と一致する場合、この軸を回転軸という。これらの回転角に対応して、2回、3回、4回、6回の回転軸がある。

    A symmetry element of the crystallographic point group. When the whole crystal (constituent atoms) is rotated by a certain angle (180°, 120°, 90° or 60°) with respect to a line, the rotated crystal can be equivalent to the crystal before rotation. In this case, this line is called "rotation axis." Corresponding to the respective rotation angles, there exist 2-fold, 3-fold, 4-fold and 6-fold rotation axes.

  • 回転対称レンズ

    rotationally symmetric lens



    A lens whose symmetry does not change even when rotated with respect to the lens axis. Conventionally-used lenses (objective lens, condenser lens, etc.) are "rotationally symmetric lenses." On the other hand, recently-developed lenses for analytical purposes, such as the Wien filter, the omega filter, the alfa filter and the Cs corrector, are non-rotationally symmetric lenses.

  • 回反軸

    rotary-inversion axis



    A symmetry element of the crystallographic point group. When the whole crystal (constituent atoms) is rotated by an angle of 90° with respect to a line, and successively an inversion is operated for the rotated crystal, the resultant crystal can be equivalent to the crystal before the operations. In this case, the combination of the two symmetries is called "rotary-inversion axis." Only the 4-fold rotary-inversion axis is a symmetry of the crystallographic point group.

  • 界面




    An "interface" is a boundary surface between two different phases. In the case of crystalline phase, the interface often takes a specific crystalline plane. In materials science, it is important to analyze grain boundaries in metals, and interfaces (boundary surfaces) on multiple layers in semiconductors and ceramics.

  • カウスティク(火面)

    caustic surface



    In the ideal (aberration-free) lens, all the electrons that exit from a point on the object plane converge at a point on the image plane, and trajectories of adjacent electron beams do not intersect each other. However, in an actual lens with aberration, the adjacent trajectories intersect and the trace of intersections forms a bright envelope surface. The bright surface is called the "caustic surface."

  • 可干渉性




    "Coherence" is used to indicate the degree of the capability of interference of the electrons emitted from an electron gun. The spatial coherence length of the electrons exiting from the electron source, i.e., the interference distance along the direction perpendicular to the traveling direction of the electrons is determined by the source size and the wavelength of the electrons. A highly coherent electron source is essential for electron holography, where the electron waves are directly brought into interference. Such an electron source or a small-sized source is also required for taking a high-contrast crystal structure image formed. The temporal coherence length, i.e., the interference distance along the traveling direction of the electrons is determined by the monochromaticity and wavelength of the electrons exiting from the source. The temporal coherence has not become a matter of discussion yet in the case of TEM.

  • 化学結合状態

    chemical-bonding state



    "Chemical-bonding state" means the energy and momentum of electrons which connect atoms to each other in a molecule or crystal. EELS enables us to perform detailed analysis of the chemical-bonding state.

  • 化学研磨

    chemical polishing



    "Chemical polishing" is a technique used for thinning inorganic materials of semiconductors and insulators. In this technique, a specimen is immersed in a polishing solution that is mainly composed of strong acid or strong alkali. Then, the specimen is thinned with its surface kept smooth. The advantage of chemical polishing is that thin specimens can be made with no mechanical distortion stress. Normally, a polishing solution that does not cause selective dissolution (etching) is used. When a particular layer in a multi-layer semiconductor is required to observe, a specified solution is used, which dissolves other layers while leaving the particular layer.

  • 化学固定

    chemical fixation



    Chemical fixation is a technique to fix a specimen with chemicals to prevent autolysis by the action of enzymes and deformation of morphologies during specimen preparation.  Biological tissues start autolysis caused by their enzymes immediately after stopping the activities of them. For the TEM observation of a biological specimen, the specimen must be prepared by removing water to preserve its morphologies under vacuum in the microscope column, and by thinning the specimen to transmit an electron beam.  For these requests, dehydration, resin embedding and thin sectioning are applied, but the procedures cause deformation of fine structures of the specimen. Chemical fixation is carried out to preserve the morphologies and physical properties at the living states of the specimen as much as possible.  This technique prevents the autolysis and deformation by cross-linking the proteins or lipids of biological materials using chemicals.  Chemical fixation for a TEM is performed by the two steps, prefixation and postfixation.

  • 化学シフト

    chemical shift



    "Chemical shift" in solid state physics means that the energy level of an inner-shell electron changes when the valence number (chemical state) changes. For example, if one valence electron is removed from an atom, inner-shell electrons are further attracted to the nucleus of the atom and the energy level of the inner-shell electrons shifts to a lower level. Thus, the energy difference between the inner-shell level and the bottom of the conduction band becomes larger. As a result, the onset energy of the EELS core-loss spectrum shifts to a higher energy. The removal of one valence electron can cause an energy shift of about 2.5 eV.

  • 化学的配列秩序/無秩序

    chemical order/disorder


    化合物や合金を構成する各元素の配列に関する秩序。例えば、二個の原子A, Bを含む化合物の場合、各原子が同一サイトをABABと交互に規則正しく配列しているとき化学的配列秩序があるといい、ランダムに配列していると無秩序な配列という。無秩序な配列は、構成原子の化学的性質が互いに似ている場合に起こる。高温で無秩序状態をとり、低温の秩序状態に相転移することがある。

    An order about the arrangement of constituent elements in a compound or an alloy. For example, in the case of a compound containing two atoms A and B, a "chemical order" implies that each atom is alternately arranged in an ordered fashion. When each atom is arranged in a random fashion, this state is called a "chemical disorder." The chemical disorder takes place when the chemical properties of the constituent atoms are similar to each other. Compounds or alloys can take a chemical disorder state at high temperature and undergo a chemical order state at low temperature.

  • 架橋




    “Cross-linking” means that target chain-like macromolecules are additionally bounded to each other with other molecules by constructing inter- or intra-molecular bridges.

  • 仮想光源

    virtual source



    In the case of the filed-emission electron gun, the action of the electrostatic lens is weak and the crossover is not produced in front of the tip of the electron gun. The "virtual source" is a point behind the tip, where all trajectories of the emitted electrons virtually meet (at one point) by the extrapolation of the electron trajectory.

  • 加速管

    acceleration tube (accelerating tube)



    The "acceleration tube" consists of acceleration electrodes used for sequentially accelerating an electron beam, which is emitted from the electron gun, up to a required voltage. In a 200 kV TEM, six acceleration electrodes constitute the acceleration tube.

  • 加速電圧

    accelerating voltage



    A voltage to accelerate electrons, which are emitted from the electron gun and illuminate a specimen. This voltage is a voltage applied between the cathode and the final electrode of the acceleration tube.

  • カソードルミネッセンス




    • 半導体の場合、入射電子によって価電子帯の電子が伝導帯に励起され、価電子帯には正孔が生成される(対生成という)。励起された自由電子と正孔はクーロン力によって結びつけられた対(自由励起子;低温で顕著に起こる)を形成する。自由励起子は不安定で任意の場所で再結合して発光する。また、生成された自由励起子を形成できない温度(通常室温以上)では電子および正孔は電荷のキャリアとして個別に半導体中を拡散する。キャリアがドナーやアクセプターとなる不純物原子に捕獲されると発光性の再結合が起こる。転位などの格子欠陥に捕獲されると非発光性の再結合が起こる。このことを利用すると、特定の波長を使ったCL像から不純物原子の空間分布が検出できる。 なお、試料の温度が上昇すると格子振動が大きくなり、格子振動を介した非発光性の再結合が増加し発光は弱まるので、多くの場合液体窒素温度程度またはそれ以下の低温で測定する必要がある。また、照射電子ビームの加速電圧が閾電圧(~100kV)を越えると点欠陥の生成が増加し、禁制帯内に深い欠陥準位が作られ、その準位を介した非発光性再結合が生じてCLの発光強度が減少するので、100kV以下の加速電圧で測定する必要がある。
    • 絶縁体の場合、酸化物や硫化物中に添加した遷移金属元素のd電子や希土類元素のf電子がつくる不純物中心や、アルカリハライド結晶中の空孔に局在した電子(この状態を色中心という)などが禁制帯内に基底準位と励起準位を形成し、それらの準位間の電子遷移で発光が起こる。この発光位置から添加元素の位置情報が得られる。加速電圧の制限は特に厳しくない。
    • 有機物では有機分子の最低非占有分子軌道(LUMO)から最高占有分子軌道(HOMO)への電子遷移によって発光する。局所的な情報は得られないが、有機分子の劣化や経年変化の情報が得られる。試料が電子線に弱いので低加速電圧での観察が求められる。

    (東工大 山本直紀氏による)

    図1 カソードルミネッセンス(CL)検出システムの概念図 ⇒図1


    図2 貫通する転位を含むGaN成長膜のTEM暗視野像、CL像とCLスペクトル(加速電圧80kV) ⇒図2

    サファイア基板上にMOCVD法で成長させたGaN膜(膜厚 4μm)を基板側からイオンミリングにより薄膜化し、エッジの薄い領域で、試料を貫通する転位を含む領域を透過電子顕微鏡(TEM)とCLにより観察した結果を示す。
    (a) TEM暗視野像。図中の矢印は転位を示す。
    (b) 同じ領域を室温において波長366nm(3.39eV)の光を使って表示した単色CL像。試料の広い領域で自由励起子(FX)発光が起こっているのが見られる(明るい部分)。矢印で示した転位のところでは、キャリアが捕獲され非発光性再結合を起こすため、暗いコントラストを示している。
    (c) 異なる試料温度で測定したCLスペクトル。主ピーク(P1)はGaNのFX発光、P2ピークは不純物が関与した発光、P3ピークはドナー・アクセプタ対発光(D,A)である。CL像で転位を明瞭に見るためにはバックグラウンドを形成するFX発光が重要である。 FX発光強度は温度の上昇とともに減少し、室温での強度は19Kに比べ2桁小さくなる。特に試料の薄い領域の観察など発光強度が弱い場合には低温での測定が必要である。転位の周囲のCL強度分布の解析からキャリアの拡散距離が求められる。

    Electrons in a solid are excited by electron-beam irradiation leaving holes. The electrons recombine with the holes to emit light (ultraviolet to infrared). This phenomenon is called "Cathodoluminescence". Cathodoluminescence is utilized as a method to analyze the electronic structure of solids in an electron microscope. The method can measure local electronic states (energy levels) of impurities and defects, the electronic states being formed between the valence band and the conduction band (in the forbidden band). Thus, the method enables the evaluation of inorganic materials containing the structural defects with a high spatial resolution (better than 1 μm) by the combined use with structural information obtained from SEM / STEM / TEM images. Applications to biological specimens, such as detection of specific proteins, have also been studied.

    • In the case of semiconductors, electrons in the valence band are excited to the conduction band by incident electrons with generating holes in the valence band (referred to as electron-hole pair generation). The excited electrons and holes form a pair (free exciton (FX): It occurs remarkably at low temperatures) bound by Coulomb force. Free excitons are unstable and recombine at arbitrary places and emit light. At room temperature or higher temperatures, the free excitons cannot be formed, thus the generated electrons and holes diffuse independently in the semiconductor as carriers. When they are trapped by impurity atoms creating donors and acceptors, radiative recombination occurs. When they are captured by lattice defects such as dislocations, non-radiative recombination occurs. For example, the distribution of impurity atoms can be detected from a CL image using a specific wavelength.
      CL measurements of semiconductors have to be conducted at liquid nitrogen temperature or lower because the luminescence intensity weakens due to the increases of non-radiative recombination through the lattice vibrations. Also, the CL measurements have to be performed with an accelerating voltage less than 100 kV. : When the accelerating voltage of the incident electron beam exceeds the threshold voltage (approx. 100 kV), the generation of point defects increases. The point defects create deep defect levels within the forbidden band and non-radiative recombinations via those levels increase, causing decrease of the luminescence intensity.
    • In the case of insulators, impurity centers are formed by d-electrons of transition elements and f-electrons of rare earth elements when they are added in oxides or sulfides, and color centers are formed at vacancies in alkali halide crystals. These electrons trapped at such localized centers produce a ground level and an excited level within the forbidden band. Light emission occurs at the electronic transition between those levels, enabling positional information on additive elements to be obtained. Restriction on the accelerating voltage of the incident electron beam is not severe.
    • In the case of organic materials, light is emitted by electronic transition from the lowest unoccupied molecular orbital (LUMO) of the organic molecule to the highest occupied molecular orbital (HOMO). Local information cannot be obtained, but information on degradation and aging of organic molecules can be obtained. Since the organic specimen is susceptible to electron-beam irradiation, observation at a low accelerating voltage is required.

    (By Naoki Yamamoto in Tokyo Institute of Technology)

    Fig.1 Schematic diagram of cathodoluminescence (CL) detection system.

    Light emitted from a specimen in a STEM (SEM) by an incident electron beam is collected and reflected by a parabolic mirror, and becomes parallel light, then guided outside the electron microscope. This light passes through the lens 1 (L1) and is focused by the lens 2 (L2) onto the slit of the spectrometer in front of the CCD detector. The spectrum of the light passing through the slit is recorded with the CCD. The incident electron beam is two-dimensionally scanned using the beam deflector controlled with a computer, and the emission spectra from each beam position are successively acquired by the CCD. After measurement, a two-dimensional monochromatic CL image is displayed by selecting a specific wavelength. From the STEM or SEM image and the CL image of the specimen, the optical properties of the structural defects are obtained.
    The luminescence ranges from infrared light (1 to 2.5 μm in wavelength) to ultraviolet light (200 nm to 380 nm). Specific gratings and detectors are used for ultraviolet-, visible- and infrared-light depending on the wavelength range. The wavelength resolution of the detector is approximately 1 nm (less than 10 meV in energy).

    Fig.2 TEM dark field image, CL image and CL spectra of GaN epitaxial film containing the dislocations penetrating the specimen (accelerating voltage 80 kV)

    A GaN epitaxial film grown by the MOCVD (metal organic chemical vapor deposition) method on a sapphire substrate (film thickness 4 μm) was thinned from the substrate side by ion milling. A transmission electron microscope (TEM) image and a CL image and CL spectra of a thin edge region containing the dislocations penetrating the specimen are shown.

    (a) TEM dark field image. Arrows in the image indicate the dislocations.

    (b) Monochromatic CL image of the same area in (a) taken at room temperature using an emission light with wavelength of 336 nm (3.39 eV).
    It is seen that free exciton (FX) emission occurs in the whole area of the specimen (bright part). Dark contrast appears at the dislocations because the carriers are captured there and non-radiative recombination occurs.

    (c) CL spectra measured at different specimen temperatures. The main peak (P1) is FX emission of GaN, the P2 peak is light emission associated with impurities, and the P3 peak is donor-acceptor pair emission (D, A). The FX emission intensity, which is important for elucidating the dislocation positions, decreases with increasing temperature, i.e., the intensity at room temperature is two orders of magnitude smaller than that at 19K. Thus, measurement at low temperature is necessary, especially for a thin specimen with a low emission intensity. From the analysis of the CL intensity distribution around a dislocation, the diffusion length of the carrier can be measured.

  • 価電子励起

    valence-electron excitation



    A phenomenon in which valence electrons are excited to the conduction band. EELS enables us to obtain the dielectric function of a substance through the valence-loss spectrum (low-loss spectrum).

  • 価電子励起スペクトル(低エネルギー損失スペクトル)

    valence-loss spectrum (low-loss spectrum)



    A spectrum in the low energy region (below ~50 eV) in an EELS spectrum is called "valence-loss spectrum (low-loss spectrum)." This spectrum enables the band gap energy (0 to 10 eV) and the plasmon energy (10 to 50 eV) to be obtained. Dielectric and optical properties of solids can be investigated from the spectrum.

  • 可動絞り

    movable aperture



    An aperture that allows selection of its hole diameter and adjustment of its position from the outside of vacuum. The "movable aperture" includes the condenser aperture, the objective aperture and the selector aperture.

  • カメラ定数

    camera constant



    The product of the camera length and the wavelength of the incident electron is called "camera constant." The camera constant is equal to the product of the distance from the central spot produced by a transmitted wave to a certain diffraction spot and the lattice spacing corresponding to the diffraction spot. Thus, if the camera constant is calculated using a standard specimen whose lattice spacing is known, measuring the distance from the transmission spot to a certain diffraction spot makes it possible to calculate the lattice spacing of the corresponding diffraction spot.

  • カメラ長

    camera length



    An effective distance from a specimen to a plane where an observed diffraction pattern is formed.

  • カロリメータ




    A device that measures the total energy of a neutral particle, a charged particle or an electromagnetic wave through absorption. An XES device equipped with a "calorimeter" provides a high energy resolution (~10 eV (recent highest data is 4.5 eV)). However, the calorimeter needs liquid helium (He), resulting into large in size. The solid angle of signal acquisition for the calorimeter is ten times or much smaller than EDS. Thus, the calorimeter is used for SEM but not for TEM.

  • 環境制御TEM

    ETEM Environmental TEM


    試料周囲にガスを導入して通常の鏡筒内真空よりも高い圧力環境下で試料観察ができるシステムを装備した透過電子顕微鏡。方式により隔膜型と差働排気型に大別される。前者は、試料ホルダ内にガス環境室(EC:environmental cell)を設ける方式である。ECにはガス導入/排気用通路が接続されるとともに環境室の上下には電子線透過用の穴が開いている。導入されたガスの鏡筒内へのリークを防ぐために、これらの穴にはカーボンや窒化ケイ素の薄膜(隔膜と呼ぶ)が貼られている。後者は、鏡筒内試料室にガスを導入する方式である。導入されたガスが鏡筒内各部に拡散して鏡筒内真空が悪化するのを防ぐために、たとえばポールピース内の上下など、試料上下の光軸上に複数組のオリフィスを組み込み、それぞれのオリフィスで仕切られた空間を差働排気している。試料と導入ガスとの間の反応過程のその場観察や含水試料観察に利用される。

    The Environmental TEM (ETEM) is a TEM which enables us to observe specimens under a gas-controlled environment. A volume around the specimen is filled with gases so that the pressure of the volume is kept higher than that of the TEM column. The ETEM is classified into two types; isolation-film type and differential pumping type. The former ETEM is equipped with an (gas) environmental cell (EC) in the specimen holder. A passage for gas introduction and evacuation is connected to the EC. There are holes above and below the EC to allow electron-beam transmission. To prevent gas leakage into the microscope column, thin films such as carbon or silicon nitride films (called "insulation films") are sealed to the holes. The latter ETEM is designed to introduce gasses into the specimen chamber in the microscope column. To prevent vacuum deterioration of the column caused by gas diffusion, differential pumping is adopted. For example, multiple orifices are incorporated into the upper and lower parts of the polepieces (on the optical axis). This construction enables differential pumping of spaces isolated by the respective orifices. The ETEM is used for in-situ observation of reaction processes between the specimen and the introduced gasses, observation of water-containing specimens, etc.

  • 干渉(電子の)

    interference of electrons



    Interference of electrons occurs due to the wave nature of electrons. When the electron waves are superposed, the amplitudes are added when their phases are the same but are canceled when their phases are opposite. When electrons travel a crystalline specimen, they are reflected by various atomic planes in the specimen (Bragg reflections) and diffracted waves are produced in various directions. When these waves meet on the TEM image plane, the waves constructively interfere where their phases are matched, whereas the waves destructively interfere where their phases are opposite. As a result, a fringe or a net image intensity modulation is formed.

  • 干渉色(超薄切片の干渉色)

    interference color of ultrathin section


    超薄切片に対し白色光を殆ど垂直に入射させた場合、切片表面からの反射光と裏面からの反射光が干渉して発する色のこと。この干渉色は切片の厚さに対応するため、この干渉色を確認することで切片のおおよその厚さを把握することができる。具体的には、厚さが約70 nmでシルバーゴールド、約100 nmでゴールド、約200 nmでブルーを発する。

    Interference color of an ultrathin section is produced by the interference of light reflected from the top- and bottom-faces of the ultrathin section when white light is incident onto a section in the almost vertical direction. Since the interference color corresponds to the thickness of the section, the interference color enables us to know a rough thickness of the section. Sections with thicknesses of about 70 nm, about 100 nm and about 200 nm emit interference colors of silver gold, gold and blue, respectively. 

  • 干渉縞(電子波による)

    interference fringe



    A series of light-and-dark fringe that is produced by interference of electron waves.

  • 環状明視野法

    ABF-STEM annular bright-field scanning transmission electron microscopy



    SrTiO3[100]入射の高分解能STEM像 ⇒
    加速電圧: 200 kV、 入射電子線の収束角: 半角22 mrad
    図(a) HAADF-STEM像。相対的に重い元素からなるSrとTi+Oコラムは輝点として明瞭に可視化されている。しかし、軽い元素であるOコラム位置では輝点を観察することはできない。検出器の取り込み角は半角90 - 170 mrad。
    図(b) ABF-STEM像。HAADF像では観察することができないOコラムを暗点として明瞭に観察することができる。検出器の取り込み角は半角11 - 22 mrad。

    2つの検出器の光線図の比較 ⇒
    図(a) HAADF-STEMにおける入射電子線の収束角と散乱電子線の検出器への取り込み角の関係。検出器の典型的な取り込み角はβ1 ~ 50 mrad、β2 ~ 200 mradである。高角度に散乱された非弾性散乱電子を検出する。200 kVの収差補正電子顕微鏡の場合、αは25 mrad程度である。通常、ABF検出器やLAADF検出器はHAADF検出器の下部に配置される。
    図(b) ABF-STEMにおける入射電子線の収束角と散乱電子線の検出器への取り込み角の関係。入射電子線の収束半角をαとすると検出器の取り込み角は、β1はα/2、β2はαと同程度に設定する。透過波の光軸中心部を用いず周辺部のみをリング状に検出する。 200 kVの収差補正電子顕微鏡の場合、α、β1、 β2はそれぞれ25 mrad、13mrad、25 mrad程度である。

    Annular bright-field scanning transmission electron microscopy (ABF-STEM) is a bright-field high-resolution STEM method which preferentially receives only the ring-shaped circumference (e.g. 12 to 24 mrad) of the direct (transmitted)-beam disk using an annular bright-field (ABF) detector, without using the central part of the bright field disk. The integrated intensities of the received electrons are displayed in synchronism with the incident probe position for acquisition of a high-resolution atomic image. The ABF method enables us to effectively visualize atomic columns composed of light atoms.
    In these light-element atomic columns, the intensities of electrons which travel along the atomic columns parallel to the incident beam, become higher than the scattered electrons due to the electron channeling effect. Thus, the electrons which are incident on the light atomic columns increase to pass through the center hole of the ABF detector. As a result, light elements are effectively imaged as dark spots (image formed by smaller quantity of electrons). On the other hand, the electrons which are incident on the heavy atomic columns increase to scatter at high angles outside of the ABF detector. As a result, heavy atomic columns are also imaged as dark spots. Thus, the ABF method enables us to observe both the atomic columns of relatively heavy elements (transition metals, etc.) and light elements (O, Li, etc.) with the same contrast.
    HREM and BF-STEM have long been used to visualize atomic columns. However, those two methods necessitate image simulations for correct image interpretation because the intensity of the atomic column largely depends on the defocus amount and specimen thickness. In the ABF-STEM image, (except for extremely thin specimen) the atoms are always imaged as dark spots irrespective of the variation of specimen thickness. Even in the image formed with a certain defocus, atoms are still imaged as dark spots because the incident electrons over a certain angular range reduce the interference effect of each electron. This makes an easy interpretation of the ABF image compared to the HREM and BF-STEM images. 

    High-resolution STEM images of SrTiO3 taken at the [100] incidence. (Accelerating voltage: 200 kV, Convergence semi-angle of the incident electron beam: 22 mrad)
    Fig.(a) HAADF-STEM image taken with an acceptance semi-angle of the detector 90 to 170 mrad. Sr columns and Ti + O columns, which are composed of relatively heavy atoms, are clearly visualized. However, the light-atom O columns cannot be observed as bright spots.
    Fig.(b) ABF-STEM image taken with an acceptance semi-angle of the detector 11 to 22 mrad.
    The light-atom O columns, which cannot be seen in the HAADF image, are clearly observed as dark spots.

    Comparison of Ray diagrams of two detectors

    Fig.(a) Relationship between the convergence semi-angle of the incident electron beam and acceptance semi-angles of the detector for HAADF-STEM. Typical inner and outer semi-angles of the detector are respectively β1 = ~50 mrad and β2 = ~200 mrad, detecting inelastically scattered electrons at high angles. The value of the convergence semi-angle α is approximately 25 mrad for a 200 kV Cs-corrected TEM. Usually, an ABF detector and a LAADF detector are placed below a HAADF detector.

    Fig.(b) Relationship between the convergence semi-angle of the incident electron beam and acceptance semi-angles of the detector for ABF-STEM. The inner and outer acceptance semi-angles of the detector are respectively taken as β1 ≒ α/2 and β2 ≒ α, where a is the convergence semi-angle. It should be noted that the only peripheral part of the bright field disk (without the central part) is used for ABF-STEM. In the case of a 200 kV Cs-corrected TEM, α, β1 and β2 are respectively ~25 mrad, ~13 mrad and ~25 mrad.

  • 緩和時間

    relaxation time



    When the external condition of a system changes and then the system reaches its equilibrium state or its steady state under the new condition, the process is called "relaxation." The "relaxation time" means the time that characterizes the velocity of the process from an initial non-equilibrium state to the final equilibrium state.

  • 外部磁場

    external magnetic field



    "External magnetic field(s)" are magnetic fields that affect an electron microscope from the outside. Measures to prevent an adverse influence of the external magnetic fields on the instrument performance are needed. The tolerable external magnetic field for the installation of the electron microscope is 1 mG or less.

  • 外乱

    external disturbance (interference)



    Noises from external electro-magnetic fields and external mechanical vibrations, which degrade the stability and performance of an electron microscope, are called "external disturbance (interference)."

  • ガウシアンフォーカス

    Gaussian focus



    A focus (imaging) condition for an ideal lens without aberrations. The image plane formed by the ideal lens is called the Gaussian plane.

  • ガウス関数

    Gaussian function


    a exp { -(x - b)2 / c2} で与えられる関数。ここで、a, b, cは定数。分光分析においてスペクトルの波形分離の際、孤立スペクトルの形状、バックグラウンドの形状を仮定するときに用いる関数。この関数をもちいてバックグラウンドの前処理やスペクトル強度のフィッティングを行う。ローレンツ関数と比較すると、ピークから離れたすそ引きの部分で少し早く減衰する。実際のスペクトルの形状はローレンツ関数のほうがよく合うが、ガウス関数は数学的に取り扱い易いので便利に用いられる。

    "Gaussian function" is a function given by a exp { - (x - b)2 / c2}, where a, b and c are constants. It is used for pre-processing of the background in a spectrum and for fitting of the spectral intensity. Compared with the "Lorentzian function," the Gaussian function damps a little quickly in its tail. Real spectral shapes are better fitted with the Lorentzian function. However, the Gaussian function is conveniently used because it is manipulated mathematically easier than the Lorentzian function.

  • ガウス/ローレンツ混合関数

    mixed Gaussian/Lorentzian function



    "Mixed Gaussian-Lorentzian function" is a function composed of a Gaussian and a Lorentzian function. It is used for pre-processing of the background in a spectrum and for fitting of the spectral intensity when the both functions are inappropriate to reproduce an experimental spectrum.

  • ガス放出




    "Outgas" means gas desorption from an object. In the case of a TEM, outgas means that deposited substances are emitted as gas from surfaces exposed to vacuum in a TEM column.

  • 画素滞在時間

    Dwell time


    Dwell timeに水平方向の走査画素数を掛け、振り戻し時間 (Flyback time)を加算すれば水平方向走査時間が得られる。水平方向走査時間に鉛直方向の走査画素数を掛ければ、走査像一枚の取得時間が計算できる。

    "Dwell time" means a time for an electron beam to stay per pixel at acquisition of a STEM image by electron-beam scan. The Dwell time is an index for the scan speed of the electron beam.
    When the Dwell time is multiplied by the number of scan pixels in one horizontal line scan, and then the Flyback time is added, the scan time for one horizontal line scan is obtained. When this scan time is multiplied by the number of the vertical scans (horizontal scan lines), the acquisition time of one scanning image is calculated.

  • ガラスナイフ

    glass knife


    使用上の注意としては: 硬いものを切ったり、同じ刃の場所で何度も切ったりすると、刃こぼれして試料表面を傷つけるので刃の位置を変えながら使用する。

    glass knife⇒

    A glass knife is a blade for a microtome. The knife is a fabricated sharp edge line of a glass made by fracturing a thick glass or a glass rod. The glass knife is used to make an exposed specimen surface flat prior to ultrathin sectioning using a diamond knife, or to perform trimming of the resin of a resin embedded specimen.
    Precautions for use; When the knife is applied to hard materials or the same position of the blade is repeatedly used, the blade tends to spill and can damage the surface of a specimen. Thus, the knife needs to be used while changing the position of the blade.

    glass knife
    Glass knife

  • ガンマカーブ

    gamma curve



    A "gamma curve" is an intensity compression curve for an observed intensity distribution to compress to a visual range when the intensity of a TEM image or a CBED pattern has a large dynamic range.

  • 機械研磨

    mechanical polishing



    "Mechanical polishing" is a physical polishing technique used for specimen preparation of TEM. The common techniques are as follows: (1) Manual polishing using water-resistant paper (down to ~100 μm thick), (2) Rotational polishing device-based polishing using diamond or corundum particles (down to ~several 10 μm thick), (3) Dimple grinder-based polishing using corundum particles (down to <10 μm thick), and (4) Tripot polisher-based polishing using diamond particles (down to <10 μm thick).

  • 幾何収差

    geometrical aberration



    In geometrical optics where electron trajectories are described as motions of charged particles in an electromagnetic field, the deviation of the real imaging point of an electron from the ideal imaging point with no aberrations is called “geometrical aberration.” Optical properties are expressed by a power-series polynomial of r (distance of an electron beam from the optical axis) and α (angle between the beam and the optical axis), in which a beam emitted from one point on the object plane is mapped to a point on the image plane. If only the first order terms of the expression is taken, the polynomial expresses ideal imaging with no aberrations (Gauss imaging). If the higher order terms than the second order are taken into account, the deviation of the real imaging point from the ideal imaging point appears.
    The order of the geometrical aberration is determined by the sum of the order of α (angle between the beam and the optical axis) and that of r (distance of an electron beam from the optical axis). It is conviniently used for describing the order of the aberration. On the other hand, the wave aberration is useful because the order of the wave aberration is closely related to the symmetry of the aberration. The order of the wave aberration is expressed by adding 1 (one) to the order of the geometrical aberration. For examples, the two-fold astigmatism is a first-order aberration in terms of the geometrical aberration but is the second-order aberration in terms of the wave aberration, and that the three-fold astigmatism is a second order in the geometrical aberration but a third order in the wave aberration.

  • 菊池図形

    Kikuchi pattern



    Kikuchi Pattern⇒
    (a)菊池ライン:結晶内のある点Oで非弾性散乱した電子が、入射電子の方向Iに対してかなり傾いた結晶面の表の面Fと裏の面Bでブラッグ反射を起こすと、ブラッグ反射位置 (方向) 1, 2に暗線と明線のペアが生ずる。これを菊池ライン(KL)という。電子線の入射方向Iに近い方(1)の菊池ライン(KL)は、B面によって反射された波とF面を透過してきた波から作られ、その強度は、その周辺に比べて低い(暗線defect)。電子線の入射方向Iから遠い方(2)の菊池ライン(KL)は、F面によって反射された波とB面を透過してきた波から作られ、その強度は周辺に比べて高い (明線excess)。
    点Oで生ずる非弾性散乱の振幅は、入射線の方向に近い低散乱角側で大きく、散乱角が大きくなるにつれて小さくなる。(入射波の方向に近い方向に非弾性散乱された電子によって)結晶の表の面Fからのブラッグ反射は、強い明線(excess KL)と強い暗線(defect KL)を形成する。(入射波の方向から遠い方向に非弾性散乱された電子によって)結晶の裏の面Bからのブラッグ反射は、表の面Fからの効果を打ち消すように働く。しかし、裏の面による強度は小さく打消しの効果は小さいので、明線の菊池線(excess KL)が入射波から遠い側(2)に、暗線の菊池線(defect KL)が入射波に近い側(1)に形成される。



    Kikuchi pattern obtained from a Si single crystal⇒

    The Kikuchi pattern is a diffraction pattern produced by Bragg reflections of inelastically scattered (thermal diffuse scattering) electrons in a specimen. Since the inelastically scattered electrons distribute over large angles, the Bragg reflections by the inelastically scattered electrons do not form diffraction spots but form a pair of excess and defect lines (Kikuchi lines) respectively by hkl and -h-k-l reflections. The low-intensity (defect) Kikuchi lines appear near side of the direction of the incident beam, whereas the high-intensity (excess) Kikuchi lines appear far side of the direction.
    When low-order reflections hkl and -h-k-l are strongly excited, a high-intensity (excess) band (Kikuchi band) is formed between the reflections due to a strong dynamical diffraction effect. Kikuchi lines appear sharply for a highly perfect and thick crystal. Kikuchi patterns are effectively used for precise adjustment of a crystal orientation by tilting the crystal for the Kikuchi lines to locate on the Bragg reflection spots.

    菊池図形 Kikuchi Pattern

    (a) Kikuch lines: When the electrons inelastically scattered at a certain point O in a crystal cause Bragg reflections from the front face (F) and the back face (B) of a crystal plane quite inclined against the direction of incident electrons I, a pair of defect intensity and excess intensity lines which are called Kikuchi lines (KL) are produced at the positions (directions) of the Bragg reflections 1 and 2. The intensity of Kikuchi line (1) near side of I is lower than that of the surrounding area (directions). To the contrary, the intensity of Kikuchi line (2) far side of I  is higher than that of the surrounding area (directions).
    The amplitude of the electrons inelastically scattered at the point O is large at low scattering angles and becomes small as the scattering angle increases. The Bragg reflection (2) from the front face (F) of a crystal plane due to the electrons inelastically scattered near the incident direction I forms strong excess and strong defect Kikuchi lines. The Bragg reflection (1) from the back face (B) of the crystal plane due to the inelastically scattered electrons far from the direction I compensates the contributions from the front face. However, since the compensation by the latter is small, the low intensity (defect) KL (1) is formed near side of I, and the high intensity (excess) KL (2) is formed far side of I.

    (b) Transformation from Kikuch lines to Kikuchi band: When the inclined angle of the crystal plane becomes small with respect to the direction of the incident electrons I, the difference of the amplitudes of inelastically scattered electrons incident on the reflection planes F and B becomes small. As a result, the bell-shaped intensity of Kikuchi lines becomes low, the symmetrical feature is lost, but an asymmetric (dispersion type) intensity starts to appear.

    (c) Kikuchi band: When the crystal plane becomes symmetric with respect to the direction of the incident electrons (I), the amplitudes of inelastically scattered electrons become equal for the Bragg reflections 1 and 2. As a result, the bell-shaped intensity vanishes and then, the dispersion type intensity is formed due to a strong dynamical diffraction effect. In the angular region between the positions (directions) 1 and 2, the intensity becomes higher than outside the region. This high intensity band is called Kikuchi band (KB).

    (d) Kikuchi pattern obtained from a Si single crystal: Many pairs of Kikuchi lines due to high-order reflections are seen. In the vicinity of a symmetric incidence, a Kikuchi band is seen between “G = 220 reflection” and “G = -2-20 reflection”. The low-intensity (defect (dark)) Kikuchi lines appear near side of the incident beam direction, whereas the high-intensity (excess (bright)) Kikuchi lines appear far side of the direction. (However the Kikuchi pattern below is shown with reversal of bright and dark.)

    Si単結晶からの菊池図形:Kikuchi pattern obtained from a Si single crystal

  • 寄生収差

    parasitic aberration


    ザイデルの5収差のようにレンズ本来の持つ収差でなく、ポールピースの材料の不均質性や機械加工の精度、レンズ間の光軸の不一致などによる残留収差のこと。軸上コマ収差、スター収差、スリーローブ、軸上(2, 3, 4, 5, 6回)非点収差がこれに当たる。

    "Parasitic aberrations" are not inherent aberrations like five Seidel aberrations, but residual aberrations which arise from magnetic non-uniformity of the polepiece material, inaccuracy of machining the polepiece and disagreement of the optical axes between lenses. The parasitic aberrations include axial coma aberration, star aberration, three lobes and axial two-, three-, four-, five- and six-fold astigmatisms.

  • 規則・不規則構造

    ordered and disordered structure



    For example, in the high-temperature phase of Cu3Au, Cu and Au randomly occupy the lattice points of the face-centered structure. In the low-temperature phase, Au occupies the position of origin and Cu occupies the three face-centered positions. In this manner, the "ordered and disordered structure" means that when the external condition (temperature) changes, the structure of a substance changes where the constituent atoms are arranged orderly or randomly. The order-disorder transformation occurs in not only alloys but also inorganic compounds. If an ordered structure is formed, diffraction spots specific to the structure appear.

  • 輝度




    "Brightness" means the current density per unit solid angle, which is a measure of the quality of an electron source. As the tip of the cathode is smaller, the brightness is higher. The brightness is kept constant at any stage of an optical system if the optical system is free from aberrations.

  • キャスタン・ヘンリー型フィルタ

    Castaing-Henry filter



    One of the in-column type energy filters, which is installed between the intermediate and projector lenses in a TEM. The filter consists of an isosceles-triangle electromagnet and an electrostatic mirror that reflects incident electrons to reverse their traveling direction. Since the "Castaing-Henry filter" exerts an electrostatic potential, the incident-electron energy is limited to 80 keV. Its energy dispersion is ~1 μm/eV for a 80 kV electron beam.

  • CAT(キャット)法

    CAT(composition analysis by thickness-fringe)method



    The "CAT" method is devised to determine the compositions of layer materials that have the same lattice spacing but have different compositions between the layers, like an artificial lattice material of AlxGa1-xAs. Utilizing the fact that the distance between thickness fringes (extinction distance) is inversely proportional to the crystal structure factor, this method determines the compositions of the different layers by measuring the difference of the extinction distances between the layers of a wedge-shaped specimen.

  • 吸収効果

    absorption effect



    In spectroscopic analysis of characteristic X-rays (EDS), the "absorption effect" means that part of X-rays generated within a specimen is absorbed by the specimen. Since this effect cannot be neglected when a specimen is thicker (~several 10 nm or thicker though depending on target elements), correction for the detected X-ray intensity is required in quantitative analysis. The correction of the absorption effect is crucial for thick specimens because this effect is larger than the atomic-number effect and the fluorescence excitation effect.

  • 吸収端エネルギー

    absorption-edge energy



    The energy to excite an electron bound to an orbit of an atom to the lowest level of the unoccupied state.

  • 吸収ポテンシャル

    absorption potential



    When incident electrons strike constituent atoms in a specimen, the incident electrons undergo inelastic scattering. Inelastically scattered electrons do not interfere constructively with elastically scattered electrons, thus giving rise to absorption or attenuation of elastic scattering. This effect can be taken into account in the elastic scattering theory through imaginary potential or "absorption potential."

  • 急速凍結固定法

    rapid freeze fixation



    Rapid freeze fixation is a technique to physically fix the morphology of biological tissues, biological cells, bacteria and suspended specimens composed of viruses, purified proteins, etc., by rapidly freezing the specimens. Chemical fixation, which is used in ordinary specimen preparation of biological tissues for TEM, may cause outflow of mineral salts, etc., in the tissues or deformation of the membrane structures of the tissues. On the other hand, rapid freeze fixation enables us to fix a specimen while preserving the morphology of the tissues. Rapid freeze fixation techniques include high pressure freezing, metal mirror freezing (slam freezing) and ice embedding.

  • 球面収差

    spherical aberration



    When an electron beam exiting obliquely from the point at the optical axis on the object plane passes through the objective lens, it does not come to the optical axis on the ideal Gaussian image plane, but intersects the optical axis at a point slightly shifted from the image plane (in the TEM, slightly before the image plane (lens side)). As a result, a circular blurred image is produced on the image plane. This defect is called "spherical aberration." The amount of blur is given by Csα3 on the object plane, where Cs is a spherical aberration coefficient and α is an angle between the electron beam and the optical axis. The spherical aberration is the most important aberration of the objective lens among the aberrations. For a rotationally symmetric lens with respect to the optical axis, the value of Cs is always positive. In TEM, the third-order spherical aberration has nowadays been successfully corrected. Cs correctors using combination of hexapoles and transfer lenses have become main stream.

  • 球面収差補正装置(Csコレクター)

    Cs corrector


    負の球面収差係数を作り出し、磁界軸対称レンズである対物レンズ、コンデンサーレンズの正の球面収差係数を打ち消す装置。1) 極性が反対の2個の六極子とそれらを繋ぐトランスファーレンズから成り、第一の六極子で負の球面収差係数を作り出す。第一の六極子で作られる不用な3回対称のビームの歪みは第二の六極子によって取り除かれる。負の球面収差は第二の六極子によって倍加される。2) 八極子と四極子を組み合わせた素子を3対用意し、第一の素子でX方向に負の球面収差を発生させ、第二の素子でY方向に、第三の素子でそれらの中間方向に負の球面収差を発生させる。対物レンズの球面収差の補正により高いTEM像分解能、コンデンサーレンズの球面収差の補正により、より小さく高強度のプローブが得られ、より高分解能のHAADF像、一原子列からの元素分析ができる。

    Cs corrector⇒ :二段六極子型球面収差補正装置

    二段六極子型球面収差補正装置では、厚みを持った六極子場が負の球面収差を発生させることを利用して収差補正を行う。左上図は、六(十二)極子内での電子線の軌道を10mradの角度毎に(内側の水色から外側の赤色の線)示したものである。一段目の六極子(Hexapole) 場で負の球面収差が発生する。軌道は本来必要の無い三角形状になってしまうが、二段目の極性が反対の六極子場で一段目の六極子場で生じた三角形状が打ち消されて円筒対称軌道に戻る。二段目の六極子は一段目の六極子と同じ負の球面収差を作り、球面収差量は二倍になる。軌道は、六極子場を励磁しない場合(黄緑色)に比べて、より発散方向(外側)に広がる(赤色)。この負の球面収差を用いて、対物レンズの正の球面収差を打ち消す。なお、右下の図中のトランスファーレンズは、一段目の六極子から出た光線をその形状を保って二段目の六極子に転送するためのもので、左上の図では、その働きは省略してある。

    The "Cs corrector" produces a negative spherical aberration coefficient (Cs) to cancel positive Cs of the objective and condenser lenses, which are axially-symmetric magnetic field lenses. The following Cs correctors are now in practical use. 1) One consists of two hexapoles with opposite polarity and transfer lenses that connect the hexapoles. The first hexapole produces a negative Cs. The unnecessary three-fold distortion produced by the first hexapole is compensated by the second hexapole. The value of negative Cs is doubled by the second hexapole. 2) The other consists of three pairs of elements combining octupoles and quadrupoles. Negative Cs is produced in the X direction by the first element, in the Y direction by the second element and the intermediate direction by the third element, respectively. Cs correction of the objective lens achieves a higher resolution TEM image. Cs correction of the condenser lens leads to a smaller, higher-intensity electron probe, thus, enabling us to obtain a higher-resolution HAADF image and to perform elemental analysis of one atomic column.
    Figure shows the schematic of a Cs corrector and its basic action. The corrector, which consists of two hexapoles with opposite polarity and transfer lenses connecting the hexapoles, produces a negative Cs and cancels a triangle shape of the beam caused by the first-stage hexapole field using the second-stage hexapole field.

    球面収差補正装置(CS corrector)
    Fig.Two-stage hexapole Cs corrector
    Electron trajectory in hexapoles or dodecapoles (upper left) and schematic of lens configuration (lower tight)

    In a two-stage hexapole Cs corrector, the thick hexapole field produces a negative Cs, and this action is used to correct the positive Cs of the objective lens. Upper left figure shows the cross section of the electron trajectory in the hexpoles for every 10 mrad angle (from inside blue line to outside red line). The first-stage hexapole field creates a negative Cs but an unwanted triangle shape trajectory. The second-stage hexapole field with the opposite polarity again creates the same amount of negative Cs and the opposite sense of triangle to cancel the triangle shape trajectory caused by the first hexapole, As a result, the amount of negative Cs is doubled and a cylindrical symmetric trajectory is retrieved. Owing to the negative Cs, the cross section of the trajectory expands outwards (shown in red), compared to the trajectory for the case of no hexapole field (in green). With the use of this negative Cs, the positive Cs of the objective lens is canceled. It should be noted that, the transfer lens (lower right figure) is used to transfer an electron beam emerged from the first-stage hexapole into the second-stage hexapole while preserving the beam shape. In the upper left figure, the action of the transfer lens is omitted.

  • 鏡映面

    mirror plane



    A symmetry element of the crystallographic point group. When the whole crystal (constituent atoms) is mirrored with respect to a certain plane, the mirrored crystal can be equivalent to the crystal before the mirror operation. In this case, this plane is called "mirror plane."

  • 境界




    In the case of crystal, a "boundary" separates crystals with different orientations or phases, or it separates crystals with different compositions or structures. Boundaries include stacking fault, twin boundary, inversion domain boundary, anti-phase domain boundary, grain boundary, and multi-layer boundary.

  • 境界条件

    boundary condition



    The boundary condition is the condition which should be satisfied by the solution function of the differential equation of a scattering problem at the boundary of a crystal. The boundary conditions in the case of the Bethe' s method for the amplitudes of transmitted and diffracted waves are as follows: 1) The amplitudes of the incident electron wave and those inside the crystal are the same at the entrance surface. 2) The tangential components of those electron waves are the same at the entrance surface.

  • 強磁性体

    ferromagnetic material



    A material that consists of atoms having magnetic moments, which align parallel to each other, thus exhibits strong spontaneous magnetic polarizations without any external magnetic field. In a magnetic domain, all the magnetic moments take the same direction. When an external magnetic field is applied to a ferromagnetic material, strong magnetic moments appear in the direction of the magnetic field, and residual magnetic moments exist even after the magnetic field is removed, thus exhibiting a hysteresis loop of the magnetic moment against the magnetic field. Certain materials show ferromagnetism below a phase transformation temperature, called the Curie temperature Tc, and are paramagnetic (disordering of the moments) above the temperature.

  • 強誘電体

    ferroelectric material



    A material that has spontaneous electric polarizations, which can be reversed by the application of an external electric field. In a ferroelectric domain, all the polarizations take the same direction. When an external electric field is applied to a ferroelectric material, strong polarizations appear in the direction of the electric field, and residual electric polarizations exist even after the electric field is removed, thus exhibiting a hysteresis loop of polarization against the external field. Certain materials show ferroelectricity below a phase transformation temperature, called the Curie temperature Tc, and are paraelectric above this temperature.

  • キラリティー(対掌性)



    右手と左手の関係ように、ある構造とその鏡像の関係にある構造が回転操作によって互いに重ね合わせることができない構造として存在することを言う。 このような構造は鏡映対称および中心対称を含まない点群に属する結晶の場合に生ずる。

    As in the case of the human left-and-right hands, "chirality" means that two certain structures having mirror-image relation to each other cannot coincide through rotation operations. These structures are possible for crystals belonging to the point groups which do not have mirror symmetry and centro-symmetry.

  • 近軸近似

    paraxial approximation


    レンズの近軸近似とは、電子線の軌道を扱うときに、電子線が光軸となす角が小さいという近似。軌道計算に現れる式の中では角度αについての三角関数を線型近似にすること(たとえばsin α → α), 光学表面を球面の一部と近似することと言いかえることもできる。近軸近似ではザイデルの5収差を生じない。

    "Paraxial approximation" is an approximation used in ray tracing of an electron beam where the angle between the electron beam and the optical axis is small. In other words, trigonometric functions of the angles appearing in ray optics are approximated by linear functions (ex. sin α → α) and optical surfaces are replaced by portions of a sphere. In the paraxial approximation, five Seidel aberrations do not appear.

  • 禁制反射

    forbidden reflection



    Even when a set of lattice planes of a crystal satisfies the Bragg condition, its reflection intensity becomes 0 or vanishes if its crystal structure factor is 0 (zero). Such a reflection is called "forbidden reflection." There are two kinds of forbidden reflections, which occur due to the type of space lattice and the symmetry element of the space group.

  • 金属




    A substance in which ions are bound with each other through free electrons (electrons extending over a crystal). The crystal structure of a "metal" is a face-centered cubic structure, a body-centered cubic structure, or a hexagonal close-packed structure. A metal exhibits high electric conductivity, high thermal conductivity and high light reflectivity, and is highly malleable as well as highly ductile.

  • 金属圧着凍結法

    metal mirror freezing (slam freezing)


    急速凍結固定法の一種。液体窒素等の冷媒で冷却した金属ブロックに生体試料を圧着して急速凍結する方法。金属ブロックの材料には、熱伝導率の高い高純度の銅に金メッキを施したものを用いることが多い。試料の温度降下効率を高めるために、金属ブロック表面は鏡面仕上げが施されている。この方法では、比較的安価な装置で凍結が行えるが、加圧凍結法に比べて試料の浅い部分(20 μm程度)しか電子顕微鏡観察に適した凍結は行えない。主に組織等を固定する際に用いられる方法である。凍結後の試料を電顕観察する際には、(1)そのまま凍結切片を作製する場合や、(2)凍結置換法を行った後に試料を室温まで戻し、樹脂包埋後、超薄切片を作製する場合や、(3)凍結割断法によりレプリカを作製する場合がある。

    Metal mirror freezing (slam freezing) is one of rapid freeze fixation techniques. This technique punches and rapidly freezes a biological specimen against a metal block cooled by a coolant such as liquid nitrogen.  In many cases, high-thermal-conductivity, high-purity copper with gold plating is used for a metal block.  To increase a temperature drop efficiency of the specimen, the surface of the metal block is prepared into a flat mirror-surface.  This technique can be performed using a relatively inexpensive device, but provides a smaller freezing depth suitable for TEM observation (about 20 µm) than the suitable depth produced by high pressure freezing.  This technique is mainly used to fix tissues.  Specimen preparation for TEM observation of the frozen specimen is carried out by one of the following three procedures.  (1) Applying freeze sectioning to the specimen, (2) Applying resin embedding and ultrathin sectioning to the specimen after the specimen is subject to freeze substitution and is returned to room temperature, and (3) Making a replica of the specimen by freeze fracturing. 

  • 金属間化合物

    intermetallic compound



    A compound that consists of two or more metallic elements.

  • 逆位相境界

    anti-phase boundary



    "Anti-phase boundary" separates two adjacent crystals which have the same crystallographic orientation but have a 180°phase shift (a shift of half period) each other. Anti-phase boundaries frequently appear in the ordered phase of a binary alloy.

  • 逆空間

    reciprocal space



    A space constructed by reciprocal lattices. In a TEM, the "reciprocal space" appears in the back focal plane of the objective lens on which a diffraction pattern is formed.

  • 逆格子

    reciprocal lattice



    "Reciprocal lattice" is a set of points which have distances inversely proportional to the spacings of lattice planes of a real lattice in the directions perpendicular to the original lattice planes. The reciprocal lattice is generated automatically from the real lattice through a mathematical relation.

  • 逆フーリエ変換

    inverse Fourier transform



    Fourier transform is a method that transforms a function of certain variables into the function of the variables conjugate to the certain variables. On the other hand, "inverse Fourier transform" is a method that transforms the Fourier-transformed function into the function of the original variable. For example, when a crystal potential as a function of position is Fourier-transformed, crystal structure factors are obtained as a function of wavenumber. Next, when the crystal structure factors are inverse-Fourier-transformed, the crystal potential as the function of position is obtained. In a TEM, Fourier transform and inverse Fourier transform of the specimen crystal are automatically executed, so that the diffraction pattern and structure image are obtained at the back focal plane and the image plane, respectively.

  • 逆流(真空ポンプオイルの)




    "Back-stream" is a phenomenon where the oil mist from the rotary pump or the diffusion pump flows to the high-vacuum side. The back-stream must be prevented.

  • 空圧ダンパ

    pneumatic damper



    A mount that absorbs vibrations using pneumatic springs. The "pneumatic damper" is used for preventing vibrations of a TEM unit.

  • 空間群(結晶空間群)

    crystallographic space group



    Since the unit cells are arranged repeatedly in a crystal, symmetry operations by which a point in a crystal is transformed to an equivalent point of a neighboring unit cell are allowed as symmetry operations leaving the crystal unchanged. These symmetry elements are screw axes and glide planes. "Crystallographic space groups" are constructed by the combinations of the screw axes and the glide planes with the symmetry elements of the crystallographic point groups. There exist 230 space groups.

  • 空間格子

    space lattice


    単位格子(平行6面体)が空間的に周期的に配列したものをいう。空間格子は、その格子定数(a, b, c, α, β, γ)の違いによって7つの結晶系に分けられる。単位格子は、その内部に格子点を持つものが可能で、面心、体心、底心格子がある。これらの格子を区別すると空間格子は14種類になり、これらをブラヴェ格子という。単純格子以外は禁制反射を引き起こす。

    "Space lattice" means a periodic array of a unit lattice (a parallelepiped) in a space. The space lattice is classified into 7 crystal systems according to lattice parameters (a, b, c, α, β, γ). Unit lattices of several crystal systems can locate within them. According to the location of the lattice points, face-centered lattice, body-centered lattice and base-centered lattice are created. As a result, it amounts to 14 type lattices, which are termed Bravais lattices. Lattices other than primitive lattice cause forbidden reflections to occur.

  • 空間周波数

    spatial frequency



    When considering an electron microscope image as a superposition of electron waves, spatial frequency is expressed as the reciprocal of wavelengths of these waves that are components of the image. The intensity distribution with respect to the spatial frequency is called "power spectrum."

  • クライオ電顕

    cryo-electron microscopy



    "Cryo-electron microscopy" is a microscopy method used for the observation of biological specimens at the temperature of liquid nitrogen or liquid helium. The biological specimens of purified proteins, viruses, lipid molecules, etc. are prepared by various freezing methods (ice embedding, freeze sectioning, etc.) without staining, and are inserted into a microscope with the specimens kept frozen. Since biological specimens are mostly composed of light elements, scattering contrast is extremely weak to observe. Thus, the specimen is observed using phase contrast produced at a defocus of a few μm.
    For inserting the low-temperature (frozen) specimens, two techniques are available: the use of a cryo-transfer holder or a dedicated cryo-electron microscope which has an automatic specimen transfer mechanism.
    3D structure analysis methods using cryo-electron microscopy include single particle analysis and tomography.

  • クライオトランスファホルダ

    cryo-transfer holder



    A specimen holder used for biological specimen observation in cryo-electron microscopy. A biological specimen on a microgrid is loaded on the specimen holder in the cryo-workstation under liquid nitrogen temperature. The holder is connected to a Dewar for Liq. N2 and the tip of the holder is maintained at the liquid-nitrogen temperature. When the holder is inserted into the electron-microscope column, the tip of the holder is exposed to the air (though in a short time), thus the holder incorporates a shutter to prevent frost deposition to the specimen.

  • クライオポンプ

    cryo pump



    The cryo-pump produces a cryogenic surface using a coolant such as liquid helium. Residual gas molecules are adsorbed to this surface resulting in a high vacuum. The working pressure is from 10-2 to 10-13 Pa. However, the pump is not suitable for adsorption of hydrogen, helium and neon. In the specimen chamber in a TEM, a fin cooled by liquid nitrogen is used to produce high vacuum.

  • クラマース-クローニッヒの関係式

    Kramers-Kronig relation



    A formula that gives the relation between the real and imaginary parts of the response function in linear response theory. In EELS, "Kramers-Kronig relation" is used when obtaining a dielectric function from the loss function of a substance.

  • クリフ・ロリマー法(薄膜近似法)

    Cliff-Lorimer method


    特性X線の分光分析(EDS)において、目的元素の定量に用いる手法で試料が数10nm以下(測定元素の違いにより変わる)の場合に適用される。薄膜近似法ともいう。たとえば二元素A、Bから成る物質の場合、特性X線強度IA、IBを測り、問題の物質のイオン化断面積、蛍光収率などに比例定数(k 因子)を用いて、元素A、Bの濃度比CA/CBを式CA/CB=k・IA/IBから求める方法。試料が薄い場合は、吸収効果、原子番号効果、蛍光励起効果の三つの効果に対する補正を行わなくても、比較的高い精度の定量ができる。試料が厚いときは、放出X線の強度は上記の三つの効果を受けるので、これらの影響を補正しなければならない(ZAF補正)。

    The Cliff-Lorimer method is a qualitative measurement method of elements in spectroscopic analysis of characteristic X-rays (EDS). It is also called the thin-film approximation method. The method is applied when a specimen thickness is 10 nm or less (though depending on measured elements). For example, when a substance is composed of two elements A and B, characteristic X-ray intensities IA and IB are measured. Then, the concentration ratio of element A to element B (CA/CB) is obtained from equation CA/CB = k・IA/IB, where k is a proportionality factor, which is determined by ionization cross sections, fluorescent yields etc. of the elements. If a specimen is thin, quantitative measurements can be performed with a relatively high accuracy even when corrections for the atomic-number effect, the absorption effect and the fluorescence excitation effect are neglected. On the other hand, if a specimen is thick, the corrections must be executed for the measured intensities (ZAF correction).

  • クロスオーバ




    An electron beam emitted from the cathode is converged by an electrostatic acceleration lens in the electron gun, and then forms the minimum cross section ahead of the cathode. The minimum cross section is termed a "crossover." The crossover is formed in the case of an electron gun fitted with a conventional tungsten emitter or a LaB6 tip. The brightness of the electron gun refers to that of the crossover.

  • クロスオーバポイント

    crossover point



    A point where the cross section of the electron beam becomes minimum when the beam is converged with the electron lens.

  • 偶発反射(非系統反射)

    accidental reflection



    "Accidental reflection(s)" are reflections excited, other than systematic reflections.

  • グリッド



    透過電子顕微鏡で観察する試料を載せる直径3 mm、厚さ20~50 μmの金属等の板のこと。四角、丸、スリットなどさまざまな形状を持つグリッドがあり、観察目的に応じて適切な形状のものを選択する。グリッドの材質には銅、モリブデン、金、チタンなどがある。元素分析をする場合は、検出目的の元素を含まない材質のグリッドを使用する。

    • 格子状のグリッド
    • 単孔グリッド
    • 文字(マーク)入りグリッド
    • FIB用グリッド


    A "grid" is a plate of a metal, etc. with a diameter of 3 mm and a thickness of 20 to 50 μm, which supports a specimen for TEM observation. Various grids such as a square-, a circular-, and a slit-grid, are available. They are selectable depending on observation requirements. The material of the grid is copper (Cu), molybdenum (Mo), gold (Au) or titanium (Ti), etc. In elemental analysis, a grid which does not contain the elements to be analyzed, is used.

    • Reticular grid
      The grid is most commonly used. Fragmented specimens are placed or pasted on the grid. For viruses or small particles, a supporting film is pasted on the grid and then, the specimen is placed on it.
    • Single hole grid
      The grid is used to observe a wide area of specimen without disturbance of the mesh of a reticular grid. Thus, it is suitable for observation at ultra-low magnifications.
    • Reference grid
      The grid is conveniently used at repeated observation of the same field because the marks (letters) to memorize the observation position are prepared on the grid.
    • FIB grid
      The grid is used to attach a thin film specimen prepared by FIB, to the heads of the grid.

    Examples of grid
     Square grid
    1. Square grid
    Single hole grid
    2. Single hole grid
    Reference grid
    3. Reference grid
    FIB grid
    4. FIB grid

  • グリーン関数

    Green's function


    グリーン関数G(r,r')は、r'にある点散乱体が点rに及ぼす影響(応答)を与える関数。電子線の動力学理論の場合のグリーン関数は(-1/4π)・exp (i k|r-r'|)/|r-r'|。

    The Green's function, G(r, r'), provides a response at point r from a point scatterer located at r'. The Green's function in the case of the dynamical theory of electron diffraction is (-1/4π)・exp (i k|r - r'|)/|r - r'|.

  • 蛍光



    蛍光とは、X線や電子線などの刺激により、物質中の電子が遷移した励起状態 (非占有状態) から放出される光(赤外線~紫外線~X線)。EDSでは蛍光X線を元素分析に用いる。結晶で、ある元素のK殻の電子が非占有状態に励起され、その元素のL殻の電子が空いたK殻に遷移するとき、元素に固有なK特性X線が放出される。

    "Fluorescence" means light (electromagnetic wave; infrared ray to ultra violet ray to X-ray) emitted from electronically excited states which are created by absorption of incident X-rays, electrons etc. In EDS, fluorescent X-rays are used for element analysis. In a crystal, an electron in the K-shell of an element is excited to an unoccupied state, and then an electron in the L-shell of the element falls to the K-shell, characteristic K X-rays inherent to the element being emitted.

  • 蛍光収率

    fluorescent yield



    A probability of radiation of electromagnetic waves emitted when an excited electron falls to the ground state.

  • 蛍光板

    fluorescent screen



    A tool to visualize TEM images and diffraction patterns. A phosphor on a "fluorescent screen" is excited through electron collision. The emitted visible light produces "light and dark (contrast)" corresponding to the electron intensities to the screen. A fluorescent material is composed of a matrix of zinc sulfide (ZnS) and a dopant of copper (Cu), aluminium (Al) or europium (Eu). A phosphor with high luminous efficiency and with a persistence of ~100 ms is chosen for the fluorescent screen. The fluorescent screen works also as a beam shutter. When acquiring a TEM image, the screen is raised. In recent years, electron microscope images are not observed on the fluorescent screen but on a computer display.

  • 蛍光励起効果

    fluorescence excitation effect



    In spectroscopic analysis of characteristic X-rays (EDS), the "fluorescence excitation effect" means that X-rays emitted from non-target elements, whose energy is higher than that of the characteristic X-rays of the target element, are absorbed by the target element and characteristic X-rays of the target element are additionally emitted. Since this effect cannot be neglected in quantitative analysis when a specimen is thicker (~several 10 nm or thicker though depending on target elements), correction for the detected X-ray intensity is required. This effect is, however, smaller than the absorption effect.

  • 計数率

    counting rate



    When the average value of the occurrence of an event is measured by a counter, "counting rate" means the number of counts per unit time.

  • 系統反射

    systematic reflection



    A series of reflections g, 2g, 3g... aligned in a certain direction (for example, 100, 200, 300...) in an electron diffraction pattern. Reflections other than "systematic reflection(s)" are called "accidental reflection(s)."

  • 結晶構造

    crystal structure


    原子、分子から成るある単位が周期的に配列したものを結晶という。その単位を単位胞と呼ぶ。単位胞内の原子配列がわかれば、結晶全体の構造を理解したことになる。 単位胞内の原子、分子の配列を結晶構造という。透過電子顕微鏡による結晶構造の詳細な解析には収束電子回折を用いる。

    "Crystal" is an object in which a unit composed of atoms and molecules is periodically arranged. The unit is called a unit cell. If we know the atomic arrangement in the unit cell, we obtain the entire knowledge of the crystal. The arrangement of atoms and molecules in the unit cell is called "crystal structure." In TEM, convergent-beam electron diffraction (CBED) is used for the detailed analysis of the crystal structure.

  • 結晶構造因子

    crystal structure factor



    The crystal structure factor gives the amplitude and phase of a diffracted wave from a crystal. The factor is determined by the atom species and their positions in a unit cell.

  • 結晶構造像

    crystal structure image



    HREM, which allows wave interference between transmitted and diffracted waves to be caused, enables us to obtain an image exhibiting the crystal structure of a thin crystalline specimen (thickness <10 nm). This image is obtained at the defocus condition, which is determined by the spherical aberration of the objective lens and the accelerating voltage of the incident beam (Scherzer focus). The image is taken by setting the electron beam parallel to a low-order zone axis and by passing a transmitted beam and many diffracted beams through the objective aperture. When the image is not taken at Scherzer focus, it is called "lattice image," which does not always correspond to the crystal structure. Three important factors to take an image corresponding to the crystal structure are: (1) Preparation of a sufficiently thin crystalline specimen, (2) High-accuracy adjustment of the crystal orientation, and (3) Adjustment of the Scherzer focus condition.

  • 結晶構造解析

    crystal structure analysis



    For crystal structure analysis, the electron microscope (TEM) image is not used, but the electron diffraction is used because the spatial resolution of the TEM is around 0.1 nm, but the electron diffraction pattern achieves a spatial resolution of 0.001 nm. In structure analysis, there are two methods; one is to use kinematical diffraction, the other is to use dynamical diffraction. The former is applied when a crystalline specimen is thin and consists of light elements and the dynamical diffraction effect can be neglected. Actually, this method is used for protein crystal analysis. The intensities of each reflection are measured from a diffraction pattern. The phases of the reflections are obtained from the real and imaginary parts of the scattering factors which are obtained by Fourier transform of the corresponding TEM image. Then, the structure is obtained by Fourier synthesis of the intensities and phases. The latter method, which uses convergent-beam electron diffraction (CBED), is applied to structure analysis of nano-scale crystals in the field of materials science. The CBED method has more advantage to study the secondary structure of solid materials, or local structures due to lattice defects and lattice strain than to study the primary structure of crystals. A disk diffraction pattern is acquired by illumination of an electron beam with an incidence angle of several 10 mrad on a small specimen area of a diameter of 10 nm or less. The acquired disk diffraction pattern (CBED pattern) exhibits a two-dimensional rocking curve (intensity distribution) corresponding to the spread of the incidence beam angle. (The CBED pattern appears to be complex due to the dynamical diffraction effect, thus the pattern is greatly different from the Laue function or the rocking curve which is expected from kinematical diffraction.) The crystal structure is solved by the fitting between the simulated CBED pattern obtained by the full dynamical calculation and the experimentally-acquired CBED pattern. Since the phases of the diffracted waves are reflected in the diffraction intensities due to multiple diffraction effects, separate determination of the phases of the diffracted waves is not necessary, which is needed in the case of kinematical diffraction. In addition, an energy filter is effectively used to remove inelastic scattering. The third method is the pre-session method. In this method, to avoid the strong dynamical diffraction effect using illumination of a cone-shaped incident beam on a crystalline specimen with a tilt angle of several degrees from a zone axis, the intensities produced by the cone illumination are added for each reflection. The crystal structure is solved by applying the kinematical theory using the obtained intensities, where the direct method for X-ray diffraction is used to estimate the phases of the diffracted waves.

  • 結晶成長

    crystal growth



    "Crystal growth" means that a single crystal or a polycrystal grows from a crystalline substance through various processes such as solidification from melt, solidification from vapor, and precipitation from solvent.

  • 結晶場分裂

    crystal field splitting



    "Crystal field splitting" means that the energy level of 3d electrons is split depending on a crystal field surrounding the 3d electrons. In the case of the perovskite structure, a transition metal having 3d electrons is located at the center of the oxygen octahedron, the energy of the eg orbital of the 3d electrons, which is faced to the oxygen atoms, is higher than that of the t2g orbital, which is pointing between the oxygen atoms. In an EELS spectrum, two peaks corresponding to the t2g and eg states due to the crystal field splitting appear when 2p electrons are excited to the 3d unoccupied band and when 1s electrons are excited to the 2p band hybridized with the 3d state.

  • 結晶方位

    crystal orientation



    "Crystal orientation" is defined by the plane (Miller) indices of the lattice plane of a crystal. In observation of an electron microscope image using a TEM, the particular crystal orientation (usually, orientation expressed by the low-order indices) is aligned to the direction of the incident electron beam. The use of a Kikuchi pattern enables us to easily align the crystal orientation with high accuracy.

  • 結像レンズ系

    imaging lens system



    The "imaging lens system" consists of the objective-, intermediate-, and projector lenses. By adjusting the excitation currents of the respective lenses, various aberrations are suppressed and image rotations are eliminated. Then, images can be taken at a wide range of magnifications, from low magnifications (~50×) to high magnifications (~1,500,000×). In addition, by changing the focal point of the first intermediate lens, a diffraction pattern is obtained.

  • 検出限界

    detection limit



    "Detection limit" is defined as the minimum quantity of a detectable specific component in various analyses. If the amount of signals falls short of the detection limit or the level of disturbance of the noise, the signals cannot be detected.

  • 検出効率

    detection efficiency



    "Detection efficiency" is defined as the ratio of the output signals to incident electrons, X-rays or photons to a detector (input signals). A detector with high detection efficiency meets various requirements, such as high conversion efficiency from input to output, short dead time, and low noise.

  • 検出立体角

    solid angle



    "Solid angle" for detection of EDS signals is a three-dimensional angle formed by the cross-sectional detection area (sphere) of the detector with respect to the incidence point of the electron beam on the specimen from which characteristic X-rays are emitted. The solid angle can be made larger for a larger detection area and a smaller distance between the specimen and the detector.

  • 検出量子効率

    DQE detective quantum efficiency



    "Detective quantum efficiency (DQE)" is the ratio of (S/N)2 of the output (detection) signal to the (S/N)2 of the input signal in various analyses. In the case of the ideal detector, DQE reaches 1.

  • 研磨




    "Polishing" is a mechanical or chemical treatment to prepare a smooth and uniform surface without selecting crystal orientations unlike etching and cleaving.

  • 検量線

    calibration curve



    A "calibration curve" provides the responses of a physical property to a certain variable as a curve. For example, if a calibration curve between the concentration of an element and the intensity of the X-ray emission from the element is provided in advance, the quantitative measurement of the element in a substance can be carried out from a measured X-ray emission intensity.

  • k 因子

    k factor


    EDSでクリフ・ロリマー法を適用する場合に使う因子。実験的にk 因子を決める場合は、目的の物質に近い組成の二元素A、Bから成る標準試料について特性X線強度IA、IB を測定し、組成CA、CB を用いて、式k=CA/CB ・IB /IAからk 因子を求める。理論的にk 因子を求める場合はk=(MAQBωBαB)/(MBQAωAαA)によって求める。ここで、M、Q、ω、αはそれぞれ原子量、イオン化断面積、蛍光収率、全K線に対するKα線の比。Qおよびωの精度は悪い。また実際には検出器窓材などによる吸収効果も考慮する必要がある。3d金属程度までの元素に対しては、k 因子に実験値を用いた場合と計算値を用いた場合で、誤差は10%程度といわれている。原子番号が大きく異なる元素から成っている物質の場合には定量精度が悪くなる。

    A factor used for the Cliff-Lorimer method in EDS analysis. For the determination of the k factor, a substance composed of two elements A and B, whose composition is similar to the target substance, is used as a standard specimen. Characteristic X-ray intensities IA and IB of the standard specimen are measured. And then the k factor is determined by equation k = CA/CB・IB /IA using the known compositions CA and CB. The k factor is theoretically given by equation k = (MAQBωBαB)/(MBQAωAαA), where M, Q, ω and α are atomic weight, ionization cross section, fluorescent yield and the ratio of Kα line to the total K lines of a substance, respectively. It is noted that the accuracies of Q and ω are low. In actual cases, the absorption due to the window material is also needed to be taken into account. For the elements up to 3d metals, it is said that the error between the quantitative analysis using experimental k factor and that with the theoretical k factor is about 10%. For a substance composed of elements with greatly different atomic numbers, the accuracy of the analysis is low.

  • ケーラー照射

    Koehler illumination


    コンデンサー ミニレンズへの励磁電流を強くし、対物レンズの前方磁界の前焦点位置に入射ビームを集束させることにより、電子線を試料に平行に照射する方法のこと。TEM像(明視野像、暗視野像、HREM像)を得るときに用いられる。試料への平行照射が崩れると、試料の場所によって回折条件が異なることになり、像の解釈に支障をきたすことがある。

    A beam illumination method, which illuminates the specimen with a parallel electron beam by increasing the excitation of the condenser mini lens so that the incident electron beam is focused onto the pre-focal point of the pre-magnetic field of the objective lens. This illumination is used for the observation of bright-field image, dark-field image and HREM image. If the parallel illumination onto the specimen is failed, the diffraction condition becomes different depending on the specimen position. This may mislead interpretation of the image.

  • 原子形状因子

    atom form factor



    A scattering amplitude of an incident electron generated by an atom. The scattering angle dependence on the scattering amplitude is given by the form of the atom. Incident electrons are scattered by the electrostatic potential that is created by an atomic nucleus and surrounding electrons. (X-rays are scattered by electrons). The atom form factor is used to calculate the crystal structure factor.

  • 原子散乱因子

    atomic scattering factor


  • 原子番号効果

    atomic-number effect



    In spectroscopic analysis of characteristic X-rays (EDS), the "atomic-number effect" means that, since the amount of incident electrons which do not contribute to the emission of the characteristic X-rays of a target element (the excitation of the electrons of the target element) due to backscattering of the incident electrons is dependent on the average atomic number, the intensity of the X-rays generated from the specimen is dependent on the atomic numbers of the constituent elements of the specimen. When the atomic numbers of constituent elements are largely different, this effect has to be considered. Since this effect cannot be neglected in quantitative analysis when a specimen is thicker (~several 10 nm or thicker though depending on measured elements), correction for the detected X-ray intensity is required.

  • 原子面

    atomic plane



    A crystal is regarded as a stacking of atomic planes, which is created by a regular array of atoms. In a (perfect) crystal, different kinds of atomic planes stack periodically.

  • 減衰




    In wave propagation, "damping" means that the amplitude of a wave is decreasing as the wave is traveling.

  • 元素マッピング

    element (elemental) mapping


    元素マッピングの主な手法には、EELSを用いるものと、EDSを用いるものの2つがある。EELSの場合、内殻電子の励起スペクトル(内殻電子励起スペクトル)中の各元素に固有の損失エネルギーをエネルギーフィルタで選択して像モードにすることにより、各元素の分布像を得る。(この説明はTEM-EELSに準拠しているが、スキャンニング法によるSTEM-EELSもある。) EDSの場合は、電子ビームを二次元走査しながら各元素に固有のX線の強度を測定し、その強度に応じた輝度変調を、走査信号と同期させてコンピュータモニタ上に表示させることにより、二次元元素分布像を得る。

    (a) EDSを用いた高空間分解能元素マップ。試料:SrTiO3、加速電圧:80kV。⇒
    電子ビームを二次元走査してX線スペクトルを取得し、元素に固有の特性X線強度 O-K, Ti-Kおよび Sr-L を走査点上に分布させた像である。RGBは各元素マップを重ね合わせたものである。

    (b) STEM-EELSを用いた高空間分解能元素マップ。試料:SrTiO3、加速電圧:80kV。⇒
    電子ビームを二次元走査して内殻電子励起スペクトルを取得し、元素に固有の損失エネルギー強度 O-K, Ti-Lおよび Sr-M を走査点上に分布させた像である。RGBは各元素マップを重ね合わせたものである。

    (c) オメガフィルタを用いたTEM-EELSにより得られた元素マップ。試料:SiC/Si3N4、加速電圧:1250kV。⇒
    TEM-EELSで内殻電子励起スペクトル(図右下)を取得し、元素に固有の損失エネルギー強度 C-K, N-K または O-Kをスリットで選択して得た各元素のエネルギーフィルタ像である。RGBは各元素マップを重ね合わせたものである。

    "Element (elemental) mapping" is carried out by using EELS spectra and EDS spectra. In the case of EELS mapping, the loss energy characteristic of each element in a core-loss spectrum is selected with the energy slit at the EELS mode, and then the mapping of the element is obtained by switching to the image mode. (This explanation is based on TEM-EELS but there is STEM-EELS method which uses the scanning technique like EDS mapping.) In the case of EDS mapping, the X-ray intensities characteristic of each element are measured while the electron beam is two-dimensionally scanned on the specimen, and then brightness modulations corresponding to the X-ray intensities are displayed on a computer monitor synchronized with the scanning signals. As a result, a two-dimensional distribution image of an element is obtained.

    element (elemental) mapping

    (a) High spatial resolution elemental maps acquired by EDS. Specimen: SrTiO3, Accelerating voltage: 80 kV.
    X-ray spectra are acquired by two-dimensionally scanning the electron beam over the specimen, and intensities of characteristic X-rays of O-K, Ti-K and Sr-L are displayed on the corresponding scanning points. RGB map is the overlay of each elemental map.

    (b) High spatial resolution elemental maps acquired by STEM-EELS. Specimen: SrTiO3, Accelerating voltage: 80 kV.
    Core-loss spectra are acquired by two-dimensionally scanning the electron beam over the specimen, and intensities of energy-loss electrons of O-K, Ti-L and Sr-M are displayed on the corresponding scanning points. RGB map is the overlay of each elemental map.
    Elemental maps acquired by TEM-EELS using an Omega filter.

    (c) Elemental maps acquired by TEM-EELS using an Omega filter. Specimen: SiC/Si3N4, Accelerating voltage: 1250 kV.
    Core-loss spectra (bottom-right figure) are acquired by TEM-EELS. Energy-loss intensities of C-K, N-K or O-K which are characteristic of respective elements are chosen with the energy selection slit. Then, the energy filtered images of the elements C, N and K are displayed as elemental maps. RGB map is the overlay of each elemental map. Elemental mapping using TEM-EELS enables to acquire a wide-field low-magnification elemental map image over an area of a few μm.

  • コアホール相互作用

    core-hole interaction


    内殻の電子が励起されて伝導帯へ遷移するとき、内殻にできたホール (内殻空孔,コアホール) と励起された電子との間のクーロン相互作用や内殻空孔が電子構造に及ぼす影響の総称。金属の場合は、自由電子がコアホールの影響を遮蔽するのでコアホール相互作用は小さいが、自由電子がない酸化物の場合には相互作用は大きい。
    酸化物などの絶縁体から得られるEELSの吸収端近傍微細構造 (ELNES) は、内殻にホールを導入しない理論計算ではよく再現されないことが知られていた。この問題を解決するために考え出されたのが、コアホール相互作用である。コアホール相互作用を取り入れてELNESスペクトルを計算すると、実験で得られる吸収端スペクトルが、理論スペクトルによって格段に良く再現されるようなる。EELSにおいて、コアホール相互作用があると吸収端が低エネルギー側にシフトする。励起された電子とホールのエネルギー差が小さいほど効果は大きい。
    図1(a)に、酸化物である酸化マグネシウム (MgO) から実験で得られたO-K ELNESスペクトルを示す。図1(b)に内殻空孔を導入しない場合の計算スペクトルを示す。計算されたスペクトルの形状が、実験で得られたスペクトルの形状に対して一致していないことが分かる。図1(c)に、酸素の内殻 (1s) に空孔を導入して、励起された電子に対するクーロン力が強くなる効果 (コアホール相互作用) を取り入れて計算したELNESスペクトルを示す。コアホール相互作用を取り入れて計算したELNESスペクトルと実験で得られたスペクトルの一致度が格段に改善していることが分かる。ELNESの理論計算のスペクトルの説明にはコアホール相互作用を考慮することの重要性が理解できる。
    図2に、中央の酸素原子 (O*) の1s軌道に、内殻空孔がない場合 (図2(a)) と内殻空孔を導入した場合 (図2(b)) の伝導帯電子の波動関数の二乗を示す。内殻空孔を導入しない場合 (図2(a)) に比べて、内殻空孔を導入した方 (図2(b)) が、波動関数の二乗の強度が中央の酸素原子近傍で高くなっている。これは、空孔を導入したために酸素原子の近傍で伝導電子の感じるクーロン力が強くなったためである。このように、コアホール相互作用は、波動関数の局所的な空間的形状に影響を及ぼしていることが分かる。
    (東京大学 溝口照康教授による)

    MgOのO-K ELNESスペクトル⇒図1
    (a) 実験で得られたELNESスペクトル
    (b) 計算によるELNESスペクトル: コアホール相互作用(内殻空孔)を導入しない場合
    (c) 計算によるELNESスペクトル: コアホール相互作用(内殻空孔)を導入した場合

    MgO (001)の伝導帯における電子の波動関数の二乗、内殻空孔の有無による違い⇒図2
    (a) コアホール相互作用(内殻空孔)を導入しない場合
    (b) コアホール相互作用(内殻空孔)を導入した場合
    酸素の1s軌道に内殻空孔を導入すると (図2(b))、導入しない場合 (図2(a)) に比べて伝導帯の波動関数の存在確率が酸素の原子近傍でより大きくなっていることが分かる。

    Core-hole interaction means a Coulomb interaction between a hole created in an inner shell (a core-hole) and an excited electron, and the effect on the electronic structure caused by the core-hole. In the case of metals, the effect of the core-hole interaction is small because the free electrons screen the effect of the hole. However, in the case of oxides, the effect is large because oxides have no free electrons.
    It has been known that conventional theoretical calculations cannot provide a good agreement with the experimental spectrum of an energy-loss near-edge structure (ELNES) in an EELS (electron energy-loss spectroscopy) spectrum obtained from an insulator (oxides, etc.). To solve this problem, the core-hole interaction has been introduced. When the ELNES spectra are calculated by taking account of the core-hole interaction, the experimental spectra are well reproduced.
    The core-hole interaction causes the absorption edge of the EELS spectrum to shift to a lower energy side. The effect of the interaction is large when the energy difference between the excited electron and the hole is small.
    Fig. 1(a) shows an experimental O-K ELNES spectrum of magnesium oxide (MgO). Fig. 2(b) shows a calculated spectrum of the same material without core-hole interaction. The two spectra do not show a good agreement in their shapes. Fig. 1(c) shows a calculated spectrum with core-hole interaction, where a core-hole is created in the inner shell (1s) of oxygen (O) and a strong Coulomb force between the hole and the excited electron is taken into account. For this spectral calculation, the core-hole interaction was taken into account, where a Coulomb force is strong against the excited electron. This spectrum is seen to show a much better agreement with the experimental spectrum. This enables us to understand the importance of the core-hole interaction for explaining the experimental ELNES spectra.
    Fig. 2 compares the wave functions of the conduction electrons between the two cases (a) without a core-hole and (b) with the core-hole in the 1s orbital of the central oxygen atom (O*). It is seen that the intensity of the wave function near the central oxygen in (a) is higher than in (b). This is because Coulomb force received by the conduction electrons in the vicinity of the oxygen atom is stronger due to creation of the core-hole. Thus, the core-hole interaction is seen to affect the local spatial distribution of the wave function.
    (By Professor Teruyasu Mizoguchi, The University of Tokyo)

    O-K ELNES spectra of MgO.
    Fig. 1 O-K ELNES spectra of MgO.
    (a) Experimental ELNES spectrum.
    (b) Calculated ELNES spectrum without the core-hole interaction.
    (c) Calculated ELNES spectrum with the core-hole interaction.
    The calculated ELNES spectrum which takes account of the core-hole interaction shows a much better agreement with the experimental spectrum.

    Fig. 2
    Squares of the wave functions of the conduction electrons of MgO (001) with and without the core hole.
    (a) Square of the wave function without the core-hole interaction.
    (b) Square of the wave function with the core-hole interaction.
    The square of the wave function of the conduction electrons in (b) is seen to be larger near the central oxygen atom than that in (a).

  • 高圧ウォブラ

    high-tension wobbler



    A function to align the optical axis to the acceleration voltage center by adding slight voltage fluctuations (~±250 V) to the accelerating voltage of the electron beam.

  • 高圧ケーブル

    high-tension cable



    A high withstand-voltage cable that connects the high-voltage power supply for accelerating an electron beam with the electron gun in an electron microscope.

  • 高圧タンク

    high-tension (voltage) tank



    A container that houses a high-voltage generator to accelerate electrons emitted from the electron gun.

  • 高圧電源

    high-voltage power supply



    A power supply that generates a high negative voltage to accelerate electrons emitted from the electron gun. The stability of the "high-voltage power supply" at present is ~1×10-6.

  • 高圧発生装置

    high-voltage generator


  • 広域エネルギー損失微細構造

    EXELFS extended energy-loss fine structure



    A fine structure appearing in an energy region of about 40 to 200 eV above the absorption-edge energy in the EELS core-loss spectrum. This structure is called "extended energy-loss fine structure (EXELFS)." The EXELFS is produced due to the scattering of electrons, which are excited from the inner-shell state to the conduction band (unoccupied state), by the adjacent atoms. When the EXELFS spectrum is Fourier-transformed, information on local atomic arrangements is obtained. EXELFS corresponds to EXAFS in X-ray spectroscopy.

  • 高角度散乱暗視野(走査透過電子顕微鏡)法

    HAADF-STEM high-angle annular dark-field scanning transmission electron microscopy


    走査透過電子顕微鏡法(STEM) の円環状検出器による暗視野法(ADF)のうち、格子振動による熱散漫散乱によって高角度に非弾性散乱された電子を円環状の検出器(~50-十分高角:たとえば200mrad)で受け、この電子の積分強度を入射電子プローブの位置に対応させて表示してSTEM像を得る手法。像強度は原子番号の1.4~2乗に比例するとされているので、重い原子がより明るく観察され、軽い原子は見えにくい。高角度に散乱された電子を使うので散乱断面積が小さく多重散乱がないこと、および電子波の干渉効果が結像に関与していない(非干渉像)ため、像の解釈が容易である。分解能は試料上の入射ビームのサイズでほぼ決まり、最高性能の装置では0.05nmを切っている。円環状検出器の中心を通り抜けた電子を使ったEELSとの併用により、原子コラムごとの元素分析ができる。一方、軽元素を効果的に可視化するSTEMとして、環状明視野法(ABF-STEM)、低角度散乱暗視野法(LAADF-STEM)という方法もある。

    図(a) HAADF-STEMにおける入射電子線の収束角と散乱電子線の検出器への取り込み角の関係。検出器の典型的な取り込み角はβ1 ~ 50 mrad,β2 ~ 200 mradである。高角度に散乱された非弾性散乱電子を検出する。200 kVの収差補正電子顕微鏡の場合、αは25 mrad程度である。通常、ABF検出器やLAADF検出器はHAADF検出器の下部に配置される。

    High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) is a STEM method which receives inelastically scattered electrons or thermal diffuse scattering (TDS) at high angles using an annular dark-field (ADF) detector (~50 to sufficiently high angle; e.g. ~200 mrad). A STEM image is acquired by displaying the integrated intensities of the electrons in synchronism with the incident probe position. As the HAADF image intensity is reported to be proportional to 1.4 square to a square of the atomic number, heavy atoms are observed brighter, but light atoms are difficult to be observed. The HAADF image is easily interpreted due mainly to two reasons.
    1) No multiple scattering arises because the scattering cross section of TDS at high angles used for the imaging is small.
    2) The interference effect of electrons does not take place for the imaging (non-interference image).
    The resolution of the HAADF image is almost determined by the incident probe diameter on the specimen. A high-performance STEM instrument provides a resolution better than 0.05 nm. A combined use with EELS, which uses electrons transmitted through the center hole of the ADF detector, enables element analysis column by column. Nowadays, the annular bright-field (ABF) STEM and the low-angle annular dark-field (LAADF) STEM are utilized as STEM methods to effectively visualize light atoms.
    Fig.(a) Relationship between the convergence semi-angle of the incident electron beam and acceptance semi-angles of the detector for HAADF-STEM. Typical inner and outer semi-angles of the detector are respectively β1 = ~50 mrad and β2 = ~200 mrad, detecting inelastically scattered electrons at high angles. The value of the convergence semi-angle α is approximately 25 mrad for a 200 kV Cs-corrected TEM. Usually, an ABF detector and a LAADF detector are placed below a HAADF detector.

  • 高加速電子

    highly accelerated electron



    An electron that is accelerated at a high voltage (>100 kV) having a high energy. As the accelerating voltage is higher, the wavelength of the electron is shorter.

  • 光学ポテンシャル

    optical potential



    A potential to which the imaginary part is added to incorporate the effect of absorption of an incident beam in a specimen. In the explanation of a TEM image using the dynamical theory, the optical potential is used. The absorption effect which gives the imaginary part of the potential includes plasmon excitation, thermal diffuse scattering and single-electron excitation. Plasmon excitation contributes to the average (normal) absorption and thermal diffuse scattering to the anomalous absorption. Single-electron excitation gives little effect to the anomalous absorption comparing to thermal diffuse scattering.

  • 後固定




    Postfixation is the second-step fixation technique of chemical fixation for biological specimens observed with a TEM.  This technique aims at preservation of lipids or enhancement of a TEM image contrast.  In the preparation of a biological specimen for TEM observation, dehydration and resin embedding are applied.  In these procedures, fixation only with aldehyde (glutaraldehyde, paraformaldehyde, etc.) cannot fix lipids in the specimen.  Thus, the membrane structures that consist of lipids flow out of the specimen when performing dehydration with ethanol or an organic solvent. In addition, aldehyde bounded to the specimen does not contribute to the enhancement of the image contrast because it consists of only light elements.  These problems are solved by postfixation with heavy metal oxide reagents (osmium tetroxide, etc.) which is a subsequent process of prefixation with aldehyde.  Osmium tetroxide fixes lipids by binding it to a double-binding region of unsaturated fatty acid and by constructing a cross-link for preventing outflow and deformation of the lipids.  In addition, osmium is a heavy metal, thus enhancing the image contrast of the binding region.  Osmium tetroxide is an effective reagent, but it has disadvantages that include slow permeation into the specimen and destruction of proteins in the specimen.  To prevent these disadvantageous phenomena, fixation (prefixation) of proteins with aldehyde is required before applying fixation with osmium tetroxide.

  • 格子欠陥

    lattice defect



    Disorder of the atomic arrangement in a crystal. In a perfect crystal, constituent atoms create a regular and an ordered arrangement. However in a real crystal, the order of arrangement is violated and structural disorder exists. "Lattice defect" is classified into planar faults, line defects and point defects, in terms of its form.

  • 格子振動

    lattice vibration



    Constituent atoms in a crystal vibrate around their equilibrium positions due to thermal energy. "Lattice vibration" means that atoms vibrate each other with a specific phase relationship. When the incident electrons on a specimen are scattered with the exciting lattice vibrations, a diffuse intensity distribution is created. This scattering is called thermal diffuse scattering.

  • 格子縞

    lattice fringe



    The lattice fringe is a periodic fringe in a TEM image, which is formed by two waves; a transmitted wave exiting from a crystal and a diffracted wave from one lattice plane of the crystal. The spacing of the fringe corresponds to that of this lattice plane.

  • 格子定数

    lattice parameter (constant)



    The lattice parameters are the quantities specifying a unit cell or the unit of the periodicity of the atomic arrangement. The lattice parameters (constants) are composed of "a, b, c," lengths of the unit cell in three dimensions, and "α, β, γ," their mutual angles.

  • 格子像

    lattice image



    HREM, which allows wave interference between transmitted and diffracted waves to be caused, enables us to obtain a lattice image of a thin crystalline specimen at an appropriate defocus of the objective lens. The lattice image (intensity distribution) does not always correspond to the electrostatic potential in the crystalline specimen projected along the direction of the incident electron beam (projected potential). However, the lattice image displays correctly the periodicity of a crystal. When the image is obtained at the defocus condition, which is determined by the spherical aberration of the objective lens and the accelerating voltage of the incident beam (Scherzer focus), it corresponds fairly well to the electrostatic potential (atomic arrangement) in the crystal. This image is called "crystal structure image."

  • 格子面

    lattice plane



    In a crystal, equivalent atomic planes are aligned in parallel with an equal distance. Thus, a crystal is regarded as an assembly of planes created by atoms. In this context, a set of parallel planes is named a "(crystal) lattice plane." The distance between the neighboring planes is termed the spacing of the plane. In a crystal, there are many lattice planes with different orientations.

  • 後焦点面

    back focal plane



    A focal plane located in the opposite side of the object (plane) with respect to a lens is called the back focal plane. A diffraction pattern is formed on the "back focal plane," thus the plane corresponds to the reciprocal space of the specimen.

  • 光軸合わせ

    optical-axis alignment



    "Optical-axis alignment" is to align the axes of the illumination and imaging systems, ranging from the electron gun to the projector lens, with the optical axis. This alignment enables the electron beam to travel in a straight path.

  • 高次ラウエ帯反射

    higher-order Laue zone (HOLZ) reflection


    入射線の方向に垂直な逆格子面をラウエ帯という。原点(入射点である逆格子点)を含むラウエ帯をゼロ次ラウエ帯(ZOLZ)と呼び、入射線の向きと反対方向に原点から数えてn番目のラウエ帯をn次ラウエ帯と呼ぶ。n = 0以外のラウエ帯を総称して高次ラウエ帯という。高次ラウエ帯(HOLZ)反射はCBED図形内の中心から離れた位置にリング状に細い線として現れる。ゼロ次ラウエ帯(ZOLZ)反射は結晶の二次元的情報しか反映しないのに対し、HOLZ反射は結晶の三次元的情報を反映する。HOLZ反射は大きな回折ベクトルを持ち、その現れる位置は格子定数のわずかの違いに敏感なので、結晶構造解析や格子歪みの高精度の解析に利用される。

    "Laue zones" are defined as the reciprocal lattice planes perpendicular to the direction of the incident beam. A Laue zone containing the point of origin (reciprocal lattice point corresponding to the incidence point) is called the zeroth-order Laue zone (ZOLZ). The Laue zone of the n-th-order counted from the point of origin in the opposite direction of the incident beam is called the n-th-order Laue zone. Laue zones other than ZOLZ are termed "higher-order Laue zones (HOLZ)." The HOLZ reflections appear as narrow ring lines at positions distant from the center of a CBED pattern. The HOLZ reflections provide three-dimensional information on a crystal, whereas, the ZOLZ reflection gives only two-dimensional information on a crystal. The HOLZ reflections have larger diffraction vectors and their positions are sensitive to a slight change of the lattice parameters. Thus, these reflections are efficiently used for high-accuracy analysis of lattice distortions and crystal structures.

  • 高精細像

    high-definition image



    "The high-definition image" means an image consisting of a small sized pixel, a wide dynamic range and high gray levels. Photo films for imaging have a pixel size of ~3 μm, a dynamic range of 2 digits and a gray scale of <16 bits. CCD has a pixel size of 13.5 μm, a dynamic range of 4 digits and gray scales of 16 bits. The imaging plate has a pixel size of 25 μm, a dynamic range of 5 to 6 digits and gray scales of 20 bits.

  • 光電子増倍管(フォトマル)

    PMT photomultiplier tube



    "Photo multiplier tube (PMT)" consists of a phototube that incorporates an electron multiplier. PMT detects weak light, and converts the light signal into an electric signal, then amplifies the electric signal (×105 to 106). PMT is used for a detector, such as a secondary-electron detector in SEM or HAADF detector for scattered electrons in TEM.

  • 高分解能像撮影

    high-resolution photography



    For "high-resolution photography," photographic films were used but have been replaced by CCD cameras. Since the pixel size of the film is ~3 μm and that of the CCD camera is ~15 μm, the magnification for the film is 300,000 to 400,000× but that for the CCD camera is 600,000 to 1,000,000×. Photography at a low magnification is recommended from the view point of specimen drift.

  • 高分解能電子顕微鏡法

    HREM high-resolution electron microscopy



    A technique of transmission electron microscopy to obtain a lattice image or a crystal structure image from a thin specimen by utilizing wave interference between transmitted and diffracted waves using a TEM equipped with a small Cs objective lens. An image which corresponds to the crystal structure is obtained by precisely adjusting the incident beam orientation to a zone axis and by setting the focus of the objective lens to Scherzer focus. The spatial resolution depends on the Cs value of the objective lens and the accelerating voltage of the incident beam. When the specimen is thick (more than 10 nm), the image obtained does not well correspond to the crystal structure due to the dynamical diffraction effect. A combined use with a HAADF-STEM image enhances the reliability of the image interpretation. HREM is used for analysis of crystal structures and lattice detects, including interface structures.

  • 後方散乱電子回折

    EBSD electron backscatter diffraction



    A Kikuchi pattern, which is produced by inelastically backscattered electrons emitted from a specimen, sensitively changes with specimen orientation. "Electron backscatter diffraction (EBSD)" is a method for obtaining crystal-orientation distribution images of crystal grains of a polycrystalline specimen. To obtain the image, the incident electron beam (probe) is scanned over the specimen surface, and the orientation change of the Kikuchi pattern is observed. EBSD provides an image with a spatial resolution of ~0.1 μm and an angular resolution of ~1°. The angular range acquired by EBSD is ~20°. Normally, EBSD is performed in a SEM though this may be performed also in a TEM.

  • 後方磁界

    post-magnetic field



    In a modern electron microscope, a specimen is placed in the objective lens. The magnetic field produced below the specimen (at the intermediate lens side) is called "post-magnetic field." Since the spherical aberration and chromatic aberration of the post-magnetic field determine the image resolution, this field is the most important part for image formation.

  • 氷包埋法

    ice embedding



    (a) 氷包埋法の概略 ⇒

    (b) 氷包埋した試料の断面図。 ⇒

    (c) 氷包埋したT4ファージのクライオTEM像。⇒

    Ice embedding is one of rapid freeze fixation techniques used for biological specimen preparation in transmission electron microscopy.
    This technique embeds a suspended specimen of biological macromolecules (purified proteins, viruses, etc.) in an amorphous ice film with a few tens of nm to a few hundreds of nm. It enables us to observe a molecular state of the specimen in a liquid solution without staining.
    In an actual experiment, a few μL suspension liquid is dropped onto a micro grid subject to hydrophilic treatment, excessive liquid is removed with a filter paper, then the specimen is rapidly frozen by immersing it into a coolant as quickly as possible. Liquid ethane or liquid propane is used commonly as a coolant because these are easy to sublimate and have a large temperature difference between the melting point and the boiling point.

    Schematic of ice embedding.
    氷包埋法の概略_Schematic of ice embedding.

    Cross sectional view of ice-embedded specimens, which are embedded in amorphous ice.
    氷包埋した試料の断面図_Cross sectional view of ice-embedded specimens.

    Cryo-TEM image of ice-embedded bacteriophage T4.
    氷包埋したT4ファージのクライオTEM像_Cryo-TEM image of ice-embedded bacteriophage T4.
    The morphology of the head and tail parts of the bacteriophage is well preserved.

  • コッククロフト・ウォルトン型高電圧回路

    CWC Cockcroft-Walton high-voltage circuit



    A multi-stage circuit that combines rectifiers and capacitors to generate a stable high DC voltage from an AC voltage. The "Cockcroft-Walton high-voltage circuit (CWC)" is used for reducing voltage fluctuations of the high-voltage power supply (high-voltage generator).

  • 固定絞り

    fixed aperture



    An aperture with a certain size fixed at an appropriate position. It includes various apertures: An fixed aperture is placed below the condenser lens to cut unnecessary beams from the electron source. A fixed aperture made of tantalum is inserted into the illumination system to cut X-rays excited in the column for achieving high-accuracy analysis. A fixed aperture is inserted at the entrance of the intermediate lens system of the imaging system to cut reflection electrons in the column. A fixed aperture is inserted below the projector lens to enable differential pumping between the camera chamber and the column part.

  • コマ収差(軸外)

    (off-axial) coma aberration



    Electron beams exit from a point that is not located at the optical axis on the object plane at various angles with respect to the optical axis do not come to one point on the image plane after passing through the lens but produce a cone-shaped (comet-shaped) image. This phenomenon is called "(off-axial) coma aberration." In this case, the vertex angle of the cone (divergence angle of the tail of the comet) is 60°. This is one of five Seidel aberrations which are inherent to the lens. It is noted that this is different from the axial parasitic coma aberration. Coma aberration is theoretically the next most important aberration to the spherical aberration for the objective lens. Although an example of off-axial coma correction has been reported, the effect of coma aberration is small for high magnification images. The name of "coma" originates from "comet."

  • コマ収差(軸上)

    axial coma aberration



    "Axial coma aberration" is a parasitic aberration due to incomplete axial symmetry of an electromagnetic lens (objective lens). This aberration deforms a circular image of the electron source to a cone-shaped (comet-shaped) image. The axial coma aberration arises from asymmetry of the pole piece bore of the lens, magnetic non-uniformity of the pole piece material, electron charging on the aperture, etc.

  • コマフリー軸

    coma-free axis



    "Coma-free axis" is an axis where the axial parasitic coma aberration of the objective lens becomes 0 (zero). Alignment of the coma-free axis means to align the incidence direction of the electron beam with the coma-free axis. The axial coma aberration is a parasitic aberration that is originated from mechanical disagreement between the axes of lenses. It should be noted that this aberration is different from the (off-axial) coma aberration among five Seidel aberrations, which is intrinsic to the lens. In the case of an electron microscope without a Cs corrector, the axial coma aberration due to the disagreement of the axis of the objective lens is corrected by the alignment coils above the specimen chamber. The coma-free axis is not so different from the accelerating voltage center. On the other hand, in the case of an electron microscope equipped with a Cs corrector, the axial coma aberration due to the disagreement of the axis of the Cs corrector is the matter of concern. A double-deflection coil system is provided for the alignment of the coma-free axis other than the alignment coil system for accelerating voltage center. The coefficient of the axial coma can be corrected to a value of a few nm. In actual alignment, using an amorphous carbon (C) thin foil or an amorphous germanium (Ge) thin film, the incident beam is tilted to more than some 10 mrads and 4 to 16 micrographs of the thin foil are taken at 0°to 360°in the azimuth directions to form a diffractogram tableau. Then, the tilt of the electron beam to the Cs corrector placed after the objective lens is adjusted so that a set of the tableau becomes centro-symmetric with respect to the center of the tableau (position at a tilt angle of 0°). This alignment is important when taking high-resolution images.

  • 固溶体

    solid solution



    When two or more kinds of substances are mixed and have a uniform structure (particularly in the case of ion crystals and semiconductors), the mixed crystal is called a solid solution. Different atoms are randomly arranged on equivalent lattice sites in the solid solution. Below a certain temperature, the different atoms can take an ordered arrangement.

  • コラム近似

    column approximation



    "Column approximation" is an approximation method to calculate the amplitudes of transmitted and diffracted waves at the bottom of a crystal, which assumes the crystal to be composed of columns. The top specimen plane, which affects the formation of an electron wave at a point on the crystal bottom plane, is deduced by Fresnel zones. The radius of the first Fresnel zone, R, is given by √(λt), where, λ is the wavelength of the electron and t is the specimen thickness. When it is assumed that λ = 0.0026 nm and t = 100 nm, the diameter of the Fresnel zone, 2R, is ~0.5 nm. If Fresnel zones are taken up to the third zone, its diameter is ~1.5 nm. That is, when the amplitude of an electron wave at a certain point on the crystal bottom plane is calculated, it is enough to consider transmission and diffraction of the electron wave in a column of 2 nm or less. When a distorted crystal is treated, the amplitudes of the transmitted and diffracted waves are calculated inside such columns, in each of which the crystal is assumed to be a perfect, and between which the crystals are shifted each other corresponding to the distortion.

  • コルニュの渦巻き

    Cornu spiral



    "Cornu spiral" is a graphical presentation of the diffraction amplitude produced by Fresnel diffraction (Fresnel integral) on the complex plane (Gaussian plane) with the integration range (length from the source to the observation point) as a variable, resulting in a spiral shape. The diffraction intensity obtained by Fresnel diffraction is calculated as the square of the length of the line drawn from the start point (corresponding to the position of the source) to the end point (the observation point) of the Cornu spiral.

  • 混晶

    mixed crystal


  • コンデンサー・オブジェクティブレンズ

    condenser-objective lens (C-O lens)


    対物レンズの前方磁界をコンデンサーレンズとして作用させ電子線を試料上に絞って照射し、後方磁界で結像するレンズ。前方磁界の縮小率は~1/100で、試料上に微小プローブを作れるので、微小領域を照射することが必要なCBED、STEM像の分解能向上、EDS、EELSの分析領域の微小化には不可欠である。HREM用の平行ビームを作るにはコンデンサー ミニレンズを使う。

    The "condenser-objective lens (C-O lens)" makes the pre-magnetic field of the objective lens act as a condenser lens so that the electron beam is focused onto the specimen, and makes the post-magnetic field act as an objective lens to form the specimen image at the image plane. Since the electron beam is demagnfied to ~1/100 by the pre-magnetic field on the specimen, the C-O lens is essential for various purposes, such as CBED that requires sub-nanometer-area illumination, improvement of STEM image resolution, and decreasing of analysis region for EDS and EELS. To produce a parallel beam for HREM in the TEM mode, a condenser mini lens is used.

  • コンデンサー絞り

    condenser aperture



    The "condenser aperture" is classified into the fixed aperture and the movable aperture. As for the former case, a fixed condenser aperture with a diameter of ~0.5 mm to 1 mm is inserted into the first condenser lens to cut unnecessary beams. As for the latter case, about five movable apertures with different diameters ranging from ~10 μm to 200 μm are inserted into the second condenser lens, which determine the divergence angle and the dose of the incident beam.

  • コンデンサーミニレンズ

    condenser mini lens


    コンデンサーレンズと対物レンズの間に置かれ、観察モードに適した収束角を持つビームを作るレンズ。対物レンズの場合のように磁場を強めるポールピースを持たない。コンデンサー ミニレンズの励磁が弱いときは、STEM、CBED、分析仕様の収束照射(微小領域照射)になる。励磁を強くすると、明暗視野像やHREM像の観察仕様の平行照射になる。

    The "condenser mini lens" is placed between the condenser lens and the objective lens for producing an electron beam with an appropriate convergence angle suitable for respective observation modes. The condenser mini lens does not have a polepiece that strengthens the magnetic field as the objective lens does. When the excitation of condenser mini lens is weak, convergent illumination of an electron beam for a nano-area for STEM, CBED and analytical use is achieved. On the other hand, when the lens excitation is strong, parallel illumination of electron beam for observation of the bright-field image, dark-field image and HREM image is achieved.

  • コンデンサーレンズ

    condenser lens



    The "condenser lens" consists of two lenses: The first lens demagnifies the crossover of the electron beam emitted from the electron gun to ~1/10 in size. The second lens transfers the demagnified beam onto the object plane of the objective lens with a magnification of ~1×.

  • コントラスト伝達関数

    CTF contrast transfer function


  • コンビネーション収差

    combination aberration



    If two thin optical elements (lenses, multi-poles, etc.) are placed at a free space, higher order aberrations than those inherent to the elements can arise due to a synergetic effect of the inherent aberrations. The higher order aberrations induced are called "combination aberrations." A thick hexapole spherical aberration corrector produces a third-order negative spherical aberration by a self-conbination effect of two three-fold astigmatism fields (second-order aberration). With the use of this third-order negative spherical aberration, the third-order positive aberration of the objective lens can be corrected. In the case of the combination between a spherical aberration (Cs) corrector and an objective lens with a free space (incomplete image transfer) between them, a positive or negative fifth-order spherical aberration is induced by a cross combination between the third-order negative aberration of the Cs corrector and the third-order positive aberration of the objective lens. Using the fifth-order spherical aberration produced, the residual fifth-order spherical aberration of the system can be removed.

  • コーティング




    "Coating" is to form a thin layer (ex. metallic layer) on the surface of a target substance.

  • 合金




    A metallic substance of a composite of intermetallic compounds or metallic phases, which contains two or more metallic elements.

  • 極表面

    top surface


    固体表面の内、特にごく薄い表面(0.5~数nm 以内)を指す。試料の極表面を加工するとか、オージェ電子は極表面から放出されるという言い方をする。

    In a solid surface, the "top surface" is defined as an extremely thin surface (~0.5 to several nm from the surface). This term is used in the following manner. (1) The top surface of a specimen is fabricated. (2) Auger electrons are emitted from the top surface.

  • 5次球面収差

    fifth-order spherical aberration


    回転対称な電界および磁界型レンズの収差のうち、電子線が光軸に対する角度αの5乗に比例する収差を、5次の球面収差という。3次のみならず5次の球面収差も電子レンズに必ず存在する。通常にいう球面収差とは、電子線が光軸に対する角度αの3乗に比例する収差を指し、収差係数の表記としてCsが使用されるのに対し、5次の球面収差の収差係数の表記にはC5が用いられることが多い。3次の球面収差補正が行われるようになり、C5の影響を考慮する必要が出てきた。幸いなことに、二段6極子とそれらを繋ぐ転送レンズを備えた3次の球面収差補正装置を用いると、C5の値を可変にすることができるので、C5 = 0にすることができる。

    Among the aberrations of rotationally symmetric magnetic and electrostatic lenses, the aberration proportional to α5 (α: an angle between an electron beam and the optical axis) is called "fifth-order spherical aberration." Not only the third-order spherical aberration, but also the fifth-order spherical aberration inevitably exists in an electron lens. The term, "spherical aberration," normally indicates the third-order aberration proportional to α3, and a symbol Cs is used as the spherical aberration coefficient. On the other hand, a symbol C5 is normaly used as the fifth-order spherical aberration coefficient. In recent years, the third-order spherical aberration has been corrected, thus the fifth-order spherical aberration has been needed to be considered. Fortunately, the use of a Cs corrector with the two-stage hexapoles and transfer lenses between them makes possible the value of C5 variable, thus C5 = 0 being available.

  • 5次の収差

    5th order aberrations


    ザイデルの5収差が、電子線の光軸への入射角αと光軸からの距離rについての3乗に比例する収差であるのに対して、次の次数である5次の収差のことで、シュワルツシルドの9収差という。Csコレクターの開発により、電子顕微鏡では3次の球面収差、および他の3次(軸上寄生)収差も補正されるようなった。(軸上)4次収差は、アライメントで補正される特徴があるため、(軸上寄生)5次収差が次に幾何的なボケの原因となる。5次の収差のうち、5次の球面収差C5α5が問題になる。しかし、(3次の)Csコレクターと転送レンズ(トランスファーレンズ)があればC5の値は可変にすることができ、C5 = 0にすることができる。二段ヘキサポール型のCsコレクターでは5次収差のうち、軸上寄生収差である6回非点収差の影響が大きく、これを小さくする努力が払われている。

    "Five Seidel aberrations" are proportional to the cube of α (angle between the incident electron beam and optical axis) and r (distance of the electron beam from the optical axis). "The 5th order aberrations" or so called "nine Schwarzschild aberrations" mean the aberrations of the next order to the Seidel aberrations or those proportional to the fifth power of α and r. Due to the development of Cs correctors, the third-order spherical aberration and third-order axial (parasitic) aberrations have nowadays been successfully corrected. The fourth-order axial (parasitic) aberrations can be corrected by the alignment of the optical axis. Thus, the fifth-order axial aberrations must be considered to decrease blurring of an image. If we have a Cs corrector with transfer lenses, the value of the fifth-order spherical aberration C5α5 is adjustable, thus C5α5 = 0 being possible. In the case of two-stage hexapole type correctors, efforts to minimize the axial (parasitic) 6-fold rotation astigmatism among the 5th order aberrations have been made.

  • ゴニオメータ・ステージ

    goniometer stage



    A stage that has a tilt mechanism. The "goniometer stage" is used for aligning the crystal orientation and for observing a specimen by tilting it with respect to the incident electron beam.

  • 最小錯乱円

    disk of least confusion


    電子レンズには球面収差があるので、物体の光軸上の一点からいろいろな方向に出射した電子線は理想像面(収差がないとしたときの結像面(ガウス像面))で一点に集まらない。光軸となす角が小さな出射ビームは理想像面に近いところに像を作り、光軸となす角が大きいビームは理想像面よりレンズに近い側に像を作る。これらを加え合わせると、理想像面から少しレンズ側にずれたところに最小の円(ディスク)像が作られる。これを最小錯乱円という。球面収差による最小錯乱円の直径dsは ds = (1/2)Csα3で与えられ、ガウス面上でのボケの1/4である。ここでCsは球面収差係数、αは電子線の光軸とのなす角。

    Since the electron lens has spherical aberration, electron beams, which exit from a point at the optical axis on the object plane while traveling in various directions, do not come to one point at the optical axis on the ideal image plane (Gaussian plane). An exiting beam, whose angle to the optical axis is small, nearly comes to the optical axis on the ideal image plane. An exiting beam, whose angle with respect to the optical axis is large, intersects the optical axis above the ideal image plane, thus deviates from the optical axis on the ideal image plane. Adding these formed images produces a least circle (disk) image at a position shifted a little from the ideal image plane to the objective lens. This circle is called "disk of least confusion." The diameter of the disk of least confusion, ds, is given by ds = (1/2)Csα3, which is 1/4 of blur on the Gaussian plane. Here, Cs is spherical aberration coefficient, α is the angle between the electron beam and the optical axis.

  • 最小二乗法

    least-squares method


    実験値と計算値の残差の二乗和を最小にするように未知パラメータを決定する方法。結晶構造解析や分光スペクトルの波形分離などに利用されている。未知パラメータの線形結合(Σai・xi + b)によって残差の二乗和を最小化する場合を(線形)最小二乗法という。フィッティングに非線形関数を用いる場合を非線形最小二乗法という。関数を仮定せず数値計算によって未知パラメータのフィッティングを行う場合も非線形最小二乗法である。たとえば、収束電子回折図形の強度と結晶構造モデルから計算される強度との残差二乗和の値を最小にするような構造パラメータ(原子位置、温度因子)を求めるのに使われる。ある構造パラメータの組について残差二乗和を求め、残差二乗和の各パラメータに対する微分が負になるような構造パラメータの組を発生させ、それらの値に対する残差二乗和を計算する。この過程を繰り返して残差二乗和の最小値に到達する。

    "Least-squares method" is a method to determine unknown parameters so that the sum of squares of the residuals between the experimental and calculated values is minimized. It is used for crystal structure analysis and spectral curve fitting. When the sum of the squares of the residuals is minimized by a liner combination of unknown parameters (∑ai・xi + b), the method is called linear least-squares method. When a nonlinear function is used for fitting, it is called nonlinear least-squares method. Nonlinear least-squares method includes cases where fitting of unknown parameters is executed by numerical calculations without assuming a specific nonlinear function. For example, nonlinear least-squares fitting is effectively used to obtain structural parameters (atom positions, Debye-Waller factors) by minimizing the sum of the squares of the residuals between the experimental intensities of CBED patterns and the calculated intensities for crystal structure models. That is, the sum of the squares of the residuals for a set of certain structural parameters is obtained. Then, a set of structural parameters is generated so that the differential of the sum is negative with respect to each parameter. Then the sum of the squares of the residuals is calculated for the set of the generated parameters. Repeating the calculation procedure reaches the minimum sum of the squares of the residuals, determining the unknown parameters.

  • サイト占有

    site occupation (occupancy)



    "Site occupation (occupancy)" means that atoms occupy specific sites. This term is particularly used in ALCHEMI to determine what impurity atoms or doped atoms occupy what sites.

  • サイドエントリー型EDS検出器

    side-entry type EDS detector



    An EDS detector which is placed on the side of the objective lens with a viewing angle of 30° or less to a specimen set horizontally. Since the "side-entry type EDS detector" can be set near the objective lens, its detection solid-angle of emitted X-rays is large or its X-ray detection efficiency is high. To improve the accuracy of quantitative analysis, the diffusion length of the emitted X-rays in the specimen is required to decrease. For this purpose, the specimen is tilted as needed against the detector so that X-rays coming to the detector take a large angle against the specimen surface. Since the X-ray intensity is sensitive to the local roughness of the specimen, the accuracy of quantitative analysis is not high enough. However, this type detector is broadly used these days as it is suitable for the analysis of a smaller specimen area because it can be combined with a high resolution objective pole-piece which has a small gap and a small bore.

  • サイドエントリーステージ

    side-entry stage



    A specimen stage into which the specimen is inserted from the side of the polepiece of the objective lens. Compared with the top-entry stage, the "side-entry stage" has disadvantages of instability to vibrations and heat. However, in the case of this stage, a space above the specimen stage can be effectively used to add analytical functions (tools) and to achieve large tilt angles of the specimen. Thus, the side-entry stage is very useful in applications to materials science and tomography. Furthermore, the advantages of this stage include: a nano-sized beam is produced on the specimen with the use of the C-O lens, and a large take-off angle of an EDS detector is achieved. Therefore, the side-entry stage is suitable for analytical electron microscopy.

  • 差動排気

    differential pumping



    "Differential pumping" means that two chambers connected through an orifice or a fine tube with high evacuation resistance are evacuated by separate pumps. Each chamber reaches the pressure determined by the performance of the pumps, without influenced by each other. The camera chamber and the column achieve differential pumping because a fixed aperture (0.5 to 2 mm in diameter) or an orifice is inserted between them. Differential pumping is also executed between the specimen chamber and the electron gun chamber.

  • サブリメーションポンプ

    sublimation pump



    In the sublimation pump, titanium is heated and sublimated under a high vacuum. A fresh titanium-deposited film is formed on the inner wall of the pump. The getter action (chemical adsorption of gas molecules) of the fresh film surface is efficient for pumping in the high-vacuum region. The working pressure is 10-5 Pa or better. Since the pump needs heating, its long-time use is inadequate to maintain a high vacuum. To overcome this problem, the sublimation pump is combined with the ion pump, where the ion pump is constantly operated and the sublimation pump is operated when needed. The pump is not used so much to date.

  • サムピーク

    sum peak



    In EDS analysis, characteristic X-rays emitted from a specimen are detected with a semiconductor detector. Pulse voltages that are proportional to the energies of the detected characteristic X-rays are generated, and then these voltages are measured with a multi-channel pulse-height analyzer. When two different characteristic X-rays almost simultaneously enter the detector, these X-rays cannot be recognized as separate pulses. Thus, an EDS spectrum exhibits a spectral peak at an energy position of the sum of energies of the two characteristic X-rays, together with spectral peaks due to characteristic X-rays of the specimen. The peak is called a "sum peak" and therefore, care must be taken for spectral analysis.

  • 3回非点収差

    three-fold astigmatism



    The three-fold astigmatism, one of the second-order axial geometrical aberrations, is a parasitic aberration exhibiting three-fold symmetry. (Note that it is called a third-order aberration in terms of the wave aberration.) The aberration is corrected using magnetic fields produced by hexapoles.
    A widely used two-stage hexapole Cs corrector corrects the spherical aberration of the objective lens using a combination effect in the three-fold astigmatism field. In the Cs correction system, the first hexapole simultaneously produces a large three-fold astigmatism and a negative spherical aberration. Then, the second hexapole placed below the first hexapole produces a three-fold astigmatism having an opposite sense to the former and a negative spherical aberration. The three-fold astigmatism produced in the first stage is canceled by that with an opposite sense produced in the second stage. The positive spherical aberration of the objective lens is corrected by the negative spherical aberration produced in the two stages.

  • 参照波

    reference wave



    In electron holography, the "reference wave" is an electron wave directly coming from the electron source, which interferes with the transmitted wave suffered by a phase shift through an object. The two waves are superposed by an electron bi-prism to obtain an electron hologram.

  • 散乱角

    scattering angle



    "Scattering angle" means the angle of an electron scattered by an atom in a specimen. It decreases with the scattering angle. The scattering amplitude is larger for the atom with a larger atomic number.

  • 散乱コントラスト

    scattering contrast



    scattering contrast ⇒
    加速電圧120 kVで取得したマウスの腎臓尿細管のTEM像。

    Incident electrons are scattered by constituent atoms in a specimen. When scattered electrons are stopped by the objective aperture, those scattered electrons act as if there arises electron absorption in the specimen. This is expressed as scattering absorption. The scattering cross section of the electron becomes larger as the mass of the atom is larger, and then image contrast produced by differences in scattering amount is termed “scattering contrast.” Since the scattering cross section for electrons is large for the atom with a large mass, the scattering contrast is sometimes called “mass contrast.” The contrast of a TEM image taken from a non-crystalline specimen is explained by the scattering contrast. In the case of a crystalline specimen, elastically scattered waves behave as diffracted waves. Thus, this image contrast is interpreted by the behavior of the diffracted waves.

    散乱コントラスト:scattering contrast
    TEM image of kidney tubules of a mouse taken at an accelerating voltage of 120 kV.

    The specimen was chemically fixed using gultaraldehyde and osmium tetroxide and then, subjected to electron staining by uranium acetate and lead citrate. The parts containing heavy elements (osmium, uranium and lead) scatter more electrons at large angles (than the areas containing light elements), and such electrons are intercepted by the objective aperture. As a result, the parts are observed with low intensity (as dark).

  • 散乱断面積

    scattering cross section



    "Scattering cross section" is a probability of scattering of an electron by an atom, expressed by unit of area. It is large at low scattering angles and becomes small at high scattering angles because the atom has a finite size.

  • ザイデルの5収差

    Five Seidel aberrations


    電子線(光線)が完全な結像をすると仮定したときの軌道からのずれの量を収差という。単色電子線(光線)が近軸電子(光)線でないために生じる3次(光線が光軸となす角度αと光線の光軸からの距離rの積について3次)の収差の総称をザイデルの5収差という。5つの収差は、球面収差(α3に比例)、(軸外)コマ収差(rα2に比例)、非点収差と像面湾曲収差(r2αに比例)、歪曲収差(r3に比例)である。電子顕微鏡の場合、像拡大の初段、すなわち対物レンズに対しては、物体の拡大する範囲は小さいので、光軸上を通る電子線(r = 0)を考えればよい。したがって像のボケにはα3に比例する球面収差が最も重要である。理論上は次にコマ収差が重要である。(軸外)コマ収差補正の例はあるが、高倍率の像については(軸外)コマ収差の効果は小さい。後段にある中間レンズおよび投影レンズでは、物体(対物レンズで拡大された像)は大きいので、光軸から離れた場所を通る電子線による収差、すなわち距離rの次数の高い収差、非点収差、像面湾曲収差、歪曲収差が重要になる。最近は球面収差補正ができるようになっている。

    Aberrations are departures of the path of electron beams from the path of the ideal (Gaussian or paraxial) imaging. The term, "(five) Seidel aberrations," is the generic name of the third-order aberrations (third order with respect to the product of α (angle between the electron beam and optical axis) and r (distance of the electron beam from the optical axis)), which occurs for a monochromatic but non-paraxial electron beam. The five aberrations are (1) spherical aberration (proportional to α3), (2) (off-axial) coma aberration (proportional to rα2), (3) off-axial astigmatism (proportional to r2α), (4) curvature of image field (proportional to r2α), and (5) distortion (proportional to r3). In the case of an electron microscope, since the specimen area magnified by the objective lens, the first-stage lens, is very small (r ~0), it is enough to consider the beams passing through the optical axis. Thus, the spherical aberration is most important for the objective lens. The (off-axial) coma aberration is next most important theoretically. Although an example of coma correction has been reported, the effect of coma aberration is small for high magnification images. Since the magnified images or the objects for the intermediate and projector lenses are not small, the aberrations produced by the beams passing through the positions distant from the optical axis give definite contributions. That is, off-axial astigmatism, curvature of image field and distortion are more important for the lenses at successive stages. In recent years, the spherical aberration has been successfully corrected.

  • ZAF(ザフ)補正法

    ZAF correction method



    In spectroscopic analysis of characteristic X-rays, the "ZAF correction method" is used for quantitative analysis of target elements. As a specimen is thicker (~several 10 nm or thicker though depending on measured elements), the intensity of the emitted characteristic X-rays is influenced by the atomic-number effect, the absorption effect and the fluorescence excitation effect. Corrections of these three effects are required. In actual correction, the relative X-ray intensities obtained from an unknown specimen against those from a standard specimen (usually a compound of a simple composition) are measured. And then, the corrections of the three effects are made to the relative intensities. In the case of EPMA, the three effects are corrected. On the other hand, in the case of TEM, only the absorption effect, which has the largest effect, is taken into account in many cases. Normally, the Cliff-Lorimer method (thin-film approximation method) for a thin specimen is applied, which often provides good quantitative results with a relatively high accuracy.

  • シェルツァー・フォーカス

    Scherzer focus



    When a high resolution structure image of a phase object is taken in the TEM mode, "Scherzer focus" is used as the defocus condition, which is determined by the spherical aberration of the objective lens so that the phase of diffracted waves is shifted by 1/4 wavelength (or a phase of π/2) of the electron wave over a wide range of spatial frequencies.

  • しきい値

    threshold value



    The minimum physical quantity (normally the minimum energy) that is required to cause reactions or other phenomenon.

  • 仕切り弁

    isolation valve



    A valve to isolate a certain part from the other part. Each "isolation valve" is placed between the electron gun chamber and the column, the specimen chamber and the column, and the column and the camera chamber, so that the vacuum in a part is broken without any effect on the vacuum in the other parts.

  • 仕事関数

    work function



    "Work function" means the energy required for removing an electron from a solid.

  • 支持膜(試料の)

    supporting film



    A "supporting film" is a thin carbon, polyvinyl formal, or collodion film with a thickness of several 10 nm or less. It is pasted on a grid to support a specimen for a TEM on the specimen holder.

  • SIT管

    silicon-intensifier-target (camera) tube


    シリコンを用いた電子増倍ターゲットによる光の撮像管。電子増倍と電荷蓄積の機能を持つので低い光量でも作動する。これを電子顕微鏡に用いるには、電子を光に変換するための蛍光スクリーンがSIT管の前に置かれる。変換された光によって受光面に生じた光電子は、数kVに加速され検出面(電子増倍ターゲット)に結像される。数kVに加速された電子がシリコンターゲットに入射すると、飛躍的な数の電子・正孔対を発生し、高い増幅率が得られる。信号の取り出しは、背後から電子ビームを操作して行われる。ダイナミックレンジが広いのが利点であるが、結像の際に、周辺部分が暗くなるのが欠点である。 現在は、増幅率は低いが、周辺部分が暗くならず、小型で安価で、ノイズ低減技術の進歩によりノイズを低減したCCDに取って代わられており、電子顕微鏡には使われていない。

    A (camera) tube for light detection using a silicon-based electron multiplication target. The "silicon-intensifier-target (camera) tube" has functions of electron-multiplication and charge-accumulation, and then operates even with a low intensity of light. To use the tube for electron microscopes, a fluorescent screen is placed at the front of the tube for converting incident electrons to light. The photoelectrons generated on the reflexible surface are accelerated to a several kV and imaged on the silicon-based target. Then, many electron-hole pairs are created, leading to a high amplification. Readout is done by sweeping an electron beam from behind the target. The advantages of the tube are high sensitivity and wide dynamic range. A disadvantage is that the surrounding part of the tube becomes dark through the lens action. Recently, the tube has been replaced with a compact and inexpensive CCD, which has unfortunately low sensitivity and narrow dynamic range but has a low noise level and does not have dark surrounding parts. Thus, the tube is not used currently for a TEM.

  • 始動圧力

    starting pressure



    When the evacuation pump can start without damage and also can perform a normal evacuation action at a certain pressure, the pressure at the start of the pump is called the "starting pressure."

  • 絞り




    The "aperture" includes the condenser aperture, the objective aperture and the selector aperture. The aperture is classified into the fixed type aperture and the movable type aperture.

  • 絞り径

    aperture diameter



    A diameter of a lens aperture. The condense-aperture diameter determines the divergence angle of an electron beam. The objective-aperture diameter determines scattering angle of electrons exiting from a specimen (the number of diffracted beams used for forming a TEM image). The selector-aperture diameter determines an area from which a diffraction pattern is obtained.

  • 写真フィルム

    photo film



    A film that records a TEM image or a diffraction pattern. The "photo film" is directly exposed to electrons in the camera chamber of a TEM. The sensitivity characteristic of the photo film to the electron is similar to that to visual light. Since the photo film has a small dynamic range of 2 digits and insufficient linearity, it is not suitable for quantitative measurement. However, since its positional resolution is as high as about 3 μm, the photo film has been used for the photography of high-definition images. Its gray level is <16 bits. Now, the imaging plate and CCD are available as recording devices that have higher sensitivity than the photo film.

  • シャドウイング




    Shadowing is a technique to obliquely deposit metals (platinum, etc.) of a high scattering power with a low angle to the specimen surface of a biological specimen composed of proteins, DNA, viruses, etc., under vacuum. By shadowing, the TEM image contrast due to roughness of the surface of those specimens is enhanced. Biological molecules, such as proteins, DNA and viruses, are composed of light elements of carbon, nitrogen, oxygen or hydrogen. When a specimen of these molecules is observed with a TEM, most incident electrons pass through the specimen without suffering scattering. As a result, an obtained image hardly shows contrast. To solve this problem, metals (platinum, etc.) are vacuum-deposited onto the molecule particles. This deposition makes it possible to enhance the contrast of the surface roughness of fine structures. As the deposition angle is lower, the finer structures can be observed. When the deposition angle is higher, the fine structures are more embedded in the deposited metal. The technique is called "shadowing" or "shadow casting" because the metal-deposited part in the TEM image appears as a shadow.

  • 収束照射

    convergence illumination



    "Convergence illumination" is to illuminate a specimen with a converged beam.

  • 集束




    "Focusing" is to focus an electron beam to carry out focusing.

  • 集束イオンビーム加工

    FIB focused ion-beam milling


    まず、薄片化してTEM観察用試料とする部分が削られないように、FIB装置内で目的とする領域に白金あるいはカーボンの保護膜を形成する(図(a))。次に、高加速(30 kV程度)のGaイオンビームで目的の領域を厚さ数µm以下の試料片に加工する (図(b))。その試料片を取り出し、TEMグリッドに固定する (図(c))。最後に、試料の損傷が少ない低加速(5 kV程度)のGaイオンビームを用いて、10~100nm以下の薄片にする(図(d))。試料表面の損傷層(Gaイオン照射によるダメージ層)が問題になる場合は、さらに低加速(3kV以下)のGaイオンビームまたはアルゴンイオンビームを用いて損傷部分を取り除く。

    図 (a)~(e)⇒

    図 (a)目的の場所を保護するためにカーボンや白金を薄膜蒸着する。(b)目的の場所の周囲をGaイオン照射によって削り、厚さ数µm以下の試料薄片を作製する。(c)試料薄片をTEMグリットに固定する。(d)目的の場所を厚さ10~100nm以下に薄片化する。(e)FIBにより薄膜化された試料をTEM観察する。

    "Focused Ion Beam (FIB) milling" is a technique of a TEM specimen preparation to mill a bulk specimen with focused gallium (Ga) ions. The target region of the bulk specimen can be selectively thinned down to a desired shape while monitoring and controlling by SEM observation of the milling region. This technique is particularly indispensible for failure analysis of semiconductor devices.
    The FIB milling procedure is as follows: First, the surface of the target region is coated with a platinum- or carbon-protective film in the FIB system to avoid the milling of the target region (Fig. (a)). Next, the target region is milled with a Ga ion beam of a high accelerating voltage of about 30 kV to prepare a section of a thickness of a few μm or less (Fig. (b)). Then, the prepared section is picked up from the bulk specimen and fixed onto a TEM specimen grid (Fig. (c)). Finally, the fixed specimen is milled with a Ga ion beam of a low accelerating voltage of about 5 kV (for decreasing damages to the specimen) to create a thin section of a thickness of 10 to 100 nm (Fig. (d)). If the damaged layers due to the irradiation of Ga ions remain, the layers are removed by another milling with a Ga ion beam of a lower accelerating voltage (about 3 kV or less) or with an argon (Ar) ion beam.

    Focused ion-beam milling

    Fig. (a) Protection layer is formed on the target region by coating of carbon or platinum. (b) Surroundings of the target region are roughly milled with Ga ion beam to prepare a section (thickness: a few μm or less). (c) A section is fixed onto a TEM grid. (d) Thin section (thickness: 10 to 100 nm) is created from the target region by fine milling. (e) The thinned section prepared by FIB is subjected to TEM observation.

  • 収束角

    convergence angle



    When a cone shaped, convergent electron beam illuminates a specimen, the semi-angle of the cone is termed "convergence angle."

  • 収束電子回折

    CBED convergent-beam electron diffraction



    CBED (a)(b)⇒
    (a) 通常の電子回折 (制限視野回折)
    (b) 収束電子回折

    CBED (c)(d)⇒
    (c) 通常の電子回折 (制限視野回折) の例。試料:Si [111]、加速電圧:200kV。
    (d) 収束電子回折図形の例(ゼロロス像)。試料:Si [111]、加速電圧:200kV。


    A method for qualitative and quantitative analysis of crystal structures from a disk diffraction pattern, acquired by illumination of a cone-shaped convergent electron beam on a small specimen area with a diameter of 10 nm or less. The CBED disk displays the intensity distribution corresponding to changes of diffraction conditions (rocking curve). The method enables us to determine not only specimen thickness, lattice parameter, crystal symmetry (point group and space group) and characteristics of a lattice defect, but also a crystal structure (refinement of atomic coordinates, Debye-Waller factors, low-order structure factors (potential distribution)). When the large-angle convergent-beam electron diffraction (LACBED) technique is applied, the characteristic feature of a lattice defect is easily and unambiguously identified and the strains (and a dislocation) at interfaces of a multi-layer material are determined with a high accuracy. The use of an energy filter allows us to conduct more accurate structure analysis.

    (a) Conventional electron diffraction (Selected-area diffraction)
    Illuminating a parallel electron beam onto a specimen forms a spot diffraction pattern on the back focal plane of the objective lens. This diffraction pattern is magnified with the imaging lens system and then displayed on a screen. In the figure, the ray path with the imaging lens system is omitted.

    (b) Convergent-beam electron diffraction
    Illuminating a cone-shaped electron beam onto a specimen forms a disk diffraction pattern on the back focal plane of the objective lens. This diffraction pattern is magnified with the imaging lens system and then displayed on a screen.
    In conventional CBED, the convergence semi-angle a is limited at the maximum to the Bragg angle q to avoid the overlap of adjacent diffraction disks.

    (c) Example of Conventional electron diffraction (Selected-area diffraction) pattern.
    Diffraction pattern of Si [111] taken at an accelerating voltage of 200 kV.

    (d) Example of Convergent-beam electron diffraction pattern.
    CBED pattern of Si [111] taken at an accelerating voltage of 200 kV by eliminating energy loss electrons (Zero-loss pattern).


  • 焼結




    "Sintering" is to heat a powder specimen until each powder in the specimen adheres to each other without melting.

  • 焼結助剤




    A material used for sintering. Yttria, etc., are used as "filler.".

  • 照射(線)量




    A "dose" is the amount of the degree of (electron-beam) irradiation. The dose is defined by the irradiation beam energy per unit area on the specimen.

  • 照射損傷

    radiation damage



    "Radiation damage" is defined as structure deterioration of a specimen due to the irradiation of an electron beam. The primary radiation damage includes the knock-on damage and the ionization damage. In the knock-on damage process, an atom that suffers the collision by an incident electron is ejected from its lattice site, forming an interstitial atom and an atomic vacancy at the corresponding lattice site. In the ionization damage process, outer-shell electrons of an atom are ejected and the atom is ionized. In a subsequent relaxation process after the primary radiation damage process, particular lattice defects or amorphous structures are created. This process is called the secondary radiation damage process.

  • 照射電流検出器

    probe-current detector



    A detector that monitors the illumination beam current onto the specimen using a Faraday cup in EELS or EDS analysis.

  • 照射レンズ系

    illumination-lens system


    コンデンサーレンズとコンデンサー ミニレンズを指す。コンデンサー・オブジェクティブレンズ(C-Oレンズ)の前方磁界も含まれる。

    The "illumination-lens system" consists of the condenser lens and condenser mini lens. The pre-magnetic field of the condenser-objective lens (C-O lens) is also included in the illumination-lens system.

  • 消衰距離

    extinction distance



    When electrons pass through a crystalline specimen and cause one Bragg reflection to occur (two-beam approximation), if an incident wave reaches a certain depth (t), its amplitude becomes 0 (zero) and the reflected wave becomes maximum. Furthermore, if the incident wave reaches a depth (2t) twice as deep as the previous depth, the amplitude of the reflected wave becomes 0 again and the amplitude of the incident wave becomes maximum. Thus, the amplitudes of the incident and reflected waves exhibit beats with the depth. The distance of one periodicity of the beats is called "extinction distance." The extinction distance is inversely proportional to the crystal structure factor of the operating reflection and the wavelength of the incident electron beam.

  • 晶帯軸

    zone axis



    In a crystal, a group of planes parallel to a certain direction is called a crystal zone, and this direction is termed a "(crystal) zone axis."

  • 焦点可変量

    focal step



    The "focal step" means the amount of change of the focal length of the objective lens, when a knob for the objective lens current is varied. The minimum focal step of a recent electron microscope is ~1 nm.

  • 焦点距離

    focal length



    When an electron passes parallel to the optical axis of a lens, the electron intersects with the optical axis at the back focal plane. The "focal length" is the distance from the center of the lens to the focal plane along the optical axis. The focal length of the objective lens ranges 0.5 to 4 mm depending on the target of observation.

  • 焦点深度

    focal depth (depth of focus)



    The "focal depth (depth of focus)" is the range of distances for which the object is imaged with an acceptable sharpness on the image plane. The focal depth is proportional to the spatial resolution of a microscope and to the square of magnification, and inversely proportional to the aperture angle. In the case of a TEM, since the aperture angle is smaller than that of an optical microscope, the focal depth is large. For example, if the magnification is 10,000×, the aperture angle is 1×10-3 rad, and the resolution is 1 nm, the focal depth reaches 100 m.

  • 焦点はずし




    In TEM image observation, the focus of the objective lens is shifted for observing Fresnel fringes or for taking a lattice image or a structure image. This focus shift is called "defocus."

  • 焦平面(焦点面)

    focal plane



    A plane that is normal to the optical axis and passes through the focal point.

  • 消滅則

    extinction rule



    A rule expressing in what case forbidden reflections occur is termed the "extinction rule." (Forbidden reflection means the extinction of reflections due to scattering factor being 0 (zero) even when the Bragg condition is satisfied.) The extinction of the reflections occurs due to the type of space lattice and due to the symmetry element of the space group. In the former case, reflections vanish even in both the kinematical diffraction case and the dynamical diffraction case. In the latter case, i.e. due to glide planes or screw axes (symmetry elements of the space group), the extinction of the reflections occurs only when kinematical diffraction applies. When the dynamical diffraction effect occurs, the forbidden reflections can have intensity. However, even when there exists the dynamical diffraction effect, extinction occurs at a part of the reflections under a specific beam incidence condition. The extinction appears as a dark line in kinematically forbidden reflections in a CBED pattern.

  • ショットキー型電子銃

    Schottky-type electron gun



    Schottky effect means a phenomenon where the potential barrier of a substance decreases in a strong electric field, resulting in ease of thermoelectron emission. In the Schottky-type electron gun, the tungsten (W) tip emitter is heated at a lower temperature (~1800 K) than the temperature that can effectively emit thermoelectrons, and a strong electric field is applied to the tip, thus decreasing the potential barrier to emit electrons from the emitter. In the actual Schottky-type electron gun, the surface of the tip is covered with a thin layer of zirconium oxide (ZrO) to make electron emission easy by a decrease of the work function of the tip (~2.7 eV). The energy spread of the emitted electrons is ~0.7 eV. Its brightness is as high as 4×108 A/cm2.sr at 200 kV. The size of the virtual source produced is >10nm. The Schottky type gun is broadly used because of its high stability of the emission current. This type of gun is not the field emission type because the tunnel effect is not used.

  • ショットキー効果

    Schottky effect



    A phenomenon where the potential barrier decreases when a strong electric field is applied to a substance. The Schottky-type electron gun emits sufficient electrons with the aid of a strong electric field at a lower temperature (~1800 K) than the temperature that can effectively emit thermoelectrons. In the actual Schottky-type electron gun, the surface of the tungsten (W) tip is covered with a thin layer of zirconium oxide (ZrO) to further decrease the potential barrier.

  • シリアル検出

    serial detection



    In the acquisition of an energy-loss spectrum in EELS, the "serial detection" method uses a single channel detector (zero-dimensional detector) and measures the energy-loss spectrum in serial times along the energy axis. Recently, a detection method for EELS has changed to parallel detection.

  • シリコンドリフト検出器

    SDD silicon drift detector


    エネルギー分散型X線検出器のひとつでEDSに用いられる。入射X線を電子-正孔対に変換する原理はSi(Li)検出器と同じ。しかしながら,同心円状の電位勾配を持つ特殊な電極構造によって素子中央の小さなアノードに効率的に電子を集めることで,静電容量が小さくなり、信号の高速応答が可能となるため、シリコン・リチウム(Si(Li))検出器と比較して、高速かつ高いS/N比で電圧パルスを取り出すことができる。そのために熱ノイズによる暗電流の影響を受けにくく、ペルチェ冷却により-15°C程度で使用できる。Si(Li)検出器と同程度のエネルギー分解能で、1桁以上高い(>1×105 cps)計数率でX線分析が可能である。液体窒素を使わないので、検出器は小型軽量である。そのため、SDDはSi(Li)検出器に代って普及しはじめている。

    One of the energy-dispersive X-ray detector used for EDS. The principle, in which characteristic X-rays entering the detector element are converted to electron-hole pairs, is the same as for the Si(Li) detector. But unlike the Si(Li)detector, electrons generated from the detector element by the incident characteristic X-rays are efficiently guided to a small anode at the center of the element by a concentric electrode structure with a potential gradient. This unique electrode structure reduces capacitance, thus enabling high-speed signal response. Thus compared with the Si(Li) detector, voltage pulses are collected with higher-speed, higher-signal-to-noise ratio. As a result, SDD may not suffer the influence from dark current due to thermal noise, and works at approximately –15 °C by Peltier cooling. SDD provides an energy resolution comparable to the Si(Li) detector and also performs X-ray analysis with high count rate (>1 x 105 cps), which is more than one order higher than the Si(Li) detector. Since it is unnecessary to use liquid nitrogen, the detector can be compactly designed. Thus SDD has more been used in place of the Si(Li) detector.

  • シリコン・リチウム検出器

    Si(Li) detector


    エネルギー分散型X線検出器のひとつでEDSに用いられる。Liをドープしたシリコン単結晶半導体を検出素子として用いている。検出素子にX線が入射すると、そのエネルギーに比例した量の電子-正孔対 (生成エネルギーは~3 eV) が素子内部に発生する。この電子を外部から電圧をかけて素子底面のアノードに集め、電圧パルスとして取り出すことでX線エネルギーを計測する。検出可能元素はB (0.18keV @K線)~U (3.16keV @M線)。エネルギー分解能は~140 eV(@Mn K線)。ドープしたLiの拡散を防ぐため、また熱ノイズによる暗電流を少なくするため、液体窒素冷却を必要とする。最近は、計数率が高くペルチェ冷却で使用可能なSDDの登場により、使用されなくなりつつある。

    One of the energy-dispersive X-ray detector used for EDS. A lithium (Li)-doped silicon single-crystal semiconductor is used as a detector element. When X-rays enter the detector element, electron-hole pairs (their generation energy is approximately 3 eV) are generated in the detector element, whose number is proportional to the energies of the X-rays. The generated electrons are collected to the anode at the bottom of the detector element by applying an external electric field. That is, the X-ray energies are measured as electric voltage pulses. Detectable elements range from boron (B: 0.18 keV @K line) to uranium (U: 3.16 keV @M line). The energy resolution of the detector is approximately 140 eV (@Mn K line). Cooling of the detector by liquid nitrogen is required to prevent diffusion of doped Li and to reduce a dark current caused by thermal noise. Owing to the development of a silicon drift detector (SDD) which has a high count rate and can be used by Peltier cooling, the Si(Li)detector has less been used.

  • 試料汚染




    Hydrocarbons deposited on a specimen surface condense at an electron-beam irradiation area by the electrostatic force of the electron beam and are polymerized by the electron beam. This phenomenon is called "(specimen) contamination." Contamination is particularly severe when a small specimen area is irradiated with a focused, high-density electron beam, for example CBED or STEM.

  • 試料汚染防止装置

    anti-contamination device



    A device that is used for suppressing the deposition of hydrocarbons on a specimen in a TEM. By the condensation action of the cooled fin with liquid nitrogen which is set to surround the specimen holder, contamination on the specimen due to hydrocarbons is largely decreased. In this device, two small aperture holes are placed at the top and bottom to allow the electron beam to pass through the holes. The tip of the specimen holder (specimen part) is inserted into the fin through the opening at its lateral side.

  • 試料回転ホルダ

    specimen rotating holder



    A specimen holder which can rotate the specimen with respect to the direction of the incident electron beam. The range of rotation angles is ±180° and the range of tilt angle is about ±25°.

  • 試料加熱1軸傾斜ホルダ

    single-tilt heating holder



    A specimen holder used to heat the specimen. The maximum temperature that can be reached is ~800 ℃. Tilt of the specimen is for only one axis (X axis) and the achievable tilt angle is ~±20°. Some holder can reach ~1000 ℃. Although the holder cannot adjust specimen orientation perfectly, it can be easily operated and is inexpensive than a double-tilt heating holder.

  • 試料加熱2軸傾斜ホルダ

    double-tilt heating holder



    A specimen holder which can heat the specimen and also tilt about the X and Y axes (double axes). The maximum temperature attained is ~800 ℃. Some holder achieves ~1000 ℃. The range of tilt angle is ~±20°.

  • 試料環境

    specimen environment



    An environment when a specimen is observed or analyzed in TEM. Various specimen environments are used, which include a high-temperature environment, a low-temperature environment, an atmospheric pressure environment, and an environment with tensile force, electric fields or magnetic fields.

  • 試料作製

    specimen preparation



    "Specimen preparation" is to prepare a suitable specimen in observation and analysis of TEM.

  • 試料ドリフト

    specimen drift



    "Specimen drift" means the amount of specimen movements that arise from thermal or mechanical instability of the goiometer, specimen holder, etc. Specimen drift is an important factor that degrades high-resolution image and micro (nano) area analysis. Normally, the drift is suppressed to ~1 nm/min.

  • 試料2軸傾斜ホルダ

    double-tilt holder



    A specimen holder in which the specimen can be tilted about the X and Y axes (double axes). Specimen tilt angle depends on the objective-lens polepiece, ranging between ±20° and ±60°.

  • 試料冷却1軸傾斜ホルダ

    single-tilt cooling holder



    A specimen holder used to cool the specimen with liquid nitrogen or liquid helium. Tilt of the specimen is for only one axis (X axis). Some liquid-helium cooling holder can be cooled down to 5 K. Although the holder cannot adjust specimen orientation perfectly, it can be easily operated and is inexpensive than a double-tilt cooling holder.

  • 試料冷却2軸傾斜ホルダ

    double-tilt cooling holder


    冷却しなおかつX軸およびY軸に関して試料を傾斜させることができるホルダ。液体窒素冷却ホルダの温度可変範囲は-175℃(~100K)~+50℃。最低温度保持時間 2~3時間。液体ヘリウム冷却ホルダの温度可変範囲は20K~100K。最低温度保持時間 約1時間。

    A specimen holder in which the specimen can be cooled and also tilted about the X and Y axes (double axes). The temperature variable range and the minimum temperature holding time of the liquid-nitrogen cooling holder are -175 ℃ (~100 K) to +50 ℃ and 2 to 3 hours, respectively. The temperature variable range and the minimum temperature holding time of the liquid-helium cooling holder are 20 K to 100 K and about 1 hour, respectively.

  • 真空蒸着

    vacuum evaporation (deposition)



    "Vacuum evaporation (deposition)" is a technique to form a thin substance layer on a surface of a substrate by evaporating the substance in high vacuum. For a TEM, this technique is used for specimen preparation of a metal and an alloy with uniform thickness.

  • 真空蒸着装置

    vacuum evaporator



    A "vacuum evaporator" is an instrument to form a thin substance layer on a surface of a substrate by vacuum evaporation (deposition). The vacuum evaporator consists of a heating element, a case and a substrate in a vacuum chamber. A substance (in most cases, a metal) that is placed in the case is evaporated by melting at high temperature, and a thin film (layer) is formed on the substrate. In specimen preparation for a TEM, a heating element, such as a tungsten (W) wire or a tantalum (Ta) plate, is resistively-heated and the substance is evaporated (deposited).

  • 真空排気系

    evacuation system



    The evacuation system of a TEM is composed of the electron gun chamber, the column, the specimen chamber and the camera chamber, and various pumps, valves, and exhaust tubes. In the normal TEM, the electron gun chamber and the column are evacuated by the (oil) rotary pump-the (oil) diffusion pump-the ion pump system, whereas the camera chamber is evacuated by the (oil) rotary pump-the (oil) diffusion pump system. When the electron gun is of the field-emission type, an independent ion pump is used for the electron gun chamber to obtain a high vacuum. Recently, due to increasing requirements for oil-free evacuation system, a system using scroll pump-turbo molecular pump is becoming popular for the evacuation of the camera chamber and the column.

  • シンチレータ(蛍光物質)

    scintillator (fluorescent substance)



    The scintillator is a substance that emits fluorescence by absorbing the energy of an electron beam or electromagnetic wave. A fluorescent substance for the "scintillator" is selected by taking account of the fluorescence wavelength (color) and its persistence time according to the sensitivity characteristic of a photoelectric converter placed behind the scintillator. The scintillator is used for various purposes: a fluorescent screen (yellow-green light, persistence light: ~100 ms) to visualize a TEM image, a secondary-electron detector (blue light, persistence light: ~μs) to measure the beam intensity of secondary electrons, and a TEM image detector (YAG) (blue white light, persistence light: ~μs) placed before a CCD.

  • 振動子強度

    oscillator strength



    "Oscillator strength" is a classical quantity corresponding to the probability of an electric dipole transition when an electron in the valence band or in the inner shell is excited to the conduction band. In the classical model, this transition can be considered as oscillations of bound electrons (harmonic oscillator) using the Lorentz model. The oscillator strength is a number of the oscillators, and corresponds to the quantum-mechanical probability of the electric dipole transition.

  • 振幅位相図

    amplitude-phase diagram


    回折した電子波の伝播を記述するとき、その波動関数の実部および虚部を複素平面上に(x0, y0)と表示するとき、原点から点x0, y0へ引いた線の距離は波の振幅を表し、その線と横軸との成す角は波の位相を表す。これを振幅位相図という。結晶をその厚さ方向に多くの層に分け、各層での回折波の振幅と位相を順次、結晶の下面まで、図形的に足し合わせてゆくと、結晶下面での回折波の強度は、原点から得られた最終座標(x, y)へ引いた線の長さの2乗として求まる。1960年代にHirschらは、振幅位相図を用いて転位や積層欠陥の像コントラストをはじめて明らかにした。

    In the case of the description of the propagation of a diffracted electron wave, let us plot the value of the wave function in the complex plane with coordinates x0, y0. The length of the line drawn from the origin to the point (x0, y0) expresses the amplitude, and the angle between the line and the horizontal axis expresses the phase of the wave. The diagram is called the "amplitude-phase diagram." When a crystal is divided into many layers in its thickness direction, the amplitude and phase of the diffracted wave in each layer is successively added until the bottom surface. The resultant intensity of the wave at the bottom surface is obtained as the square of the length of the line drawn from the origin to the final point (x, y) at the bottom surface. In 1960s, Hirsch et al., for the first time, revealed the image contrast of dislocations and stacking faults using the amplitude-phase diagram.

  • CCD

    CCD charge-coupled device


    電子線やX線の2次元のデジタル強度記録媒体として利用される高感度の光電変換用の半導体素子。光を照射して半導体表面の空乏領域(ポテンシャル井戸)に電荷を蓄積し、表面を通して隣接する井戸にこの電荷を伝達し、電気信号として外部に取り出す。電子線の検出には、蛍光材料、YAG結晶等によって電子の強度を光に変換してからCCDに露光する。CCDには暗電流があるので、それを抑えるために冷却して使用する(ペルチェ冷却で-30℃)。空間分解能(画素サイズ)14ミクロン(光用には7ミクロンもある)で~3cm平方のCCD(2K × 2K)が一般的。イメージングプレートに比べると、ダイナミックレンジは4桁、階調は16ビットと小さいが、オンラインで利用できることがイメージングプレートにない最大の利点である。高分解能像取得のためのスロースキャンCCDカメラやWDSの分光用の検出器に用いられる。さらに大きな面積のCCD(4K × 4K)の使用へと移行しつつある。

    "CCD" is a two-dimensional digital semiconductor photoelectric conversion device. For electron beam detection, electrons are converted into light by a fluorescent material or a YAG crystal. When the CCD is irradiated with light, electron charges are accumulated in the depletion region (potential wells). Then, these charges are transferred to successive wells. Finally, these charges are taken out as electric signals. Since the CCD contains a dark current, the device is cooled to suppress this current (cooled to -30 ℃ by Peltier cooling). A normally-used CCD has a size of 2K × 2K (a square of approximately 3cm) with a spatial resolution (pixel size) of 14 μm (7 μm for visible light available). Compared to the imaging plate, CCD has a smaller dynamic range of 4 digits or a gray scale of 16 bits than an imaging plate. However, the most advantage of CCD is that it can be used online (only offline use in the imaging plate). CCD is used for acquisition of a high-resolution image and for detection of X-rays in WDS. Recently, a CCD with a larger area (4K × 4K) have been getting popular.

  • ジェット研磨

    jet polishing



    "Jet polishing" is one technique in electrolytic polishing. In this technique, a jet-like polishing solution is sprayed onto a specimen to make a hole at its center. Spraying the solution makes it possible to keep the solution at the specimen surface fresh, thus a quick and smooth polishing is achieved.

  • ジェントルミリング

    gentle milling



    A surface of a specimen milled by the focused ion beam (FIB) technique or a normal ion milling technique is likely to suffer damage. To remove the damaged layers on the specimen surface, an argon ion beam at a low accelerating voltage of 100 V to 2 kV is used to gently mill the specimen surface. This technique is termed "gentle milling."

  • 磁区

    magnetic domain



    A "magnetic domain" means a region where the directions of all the magnetizations of respective atoms are the same.

  • 軸上幾何収差

    axial geometrical aberration



    The axial geometrical aberrations are aberrations depending only on α, angle between the beam and the optical axis. The axial geometrical aberrations are defocus, two-fold astigmatism, three-fold astigmatism, axial coma aberration, spherical aberration, four-fold astigmatism, star aberration, etc. On the other hand, aberrations that depend on α and r, distance of an electron beam from the optical axis, are called “off-axial (geometrical) aberrations.” As an example of the off-axial aberrations, the coma aberration of Five Seidel aberrations is mentioned.
    In the case of high-resolution electron microscopy (HREM), the field of view is very narrow because its magnification is very high. Thus, the off-axial geometrical aberrations can be ignored, enabling us to account for only the axial geometrical aberrations. In the case of scanning transmission electron microscopy (STEM), a converged electron probe on the optical axis scans a specimen area. Only the axial geometrical aberrations are accounted for in STEM image formation as in the case of HREM.

  • 自己相関関数

    auto-correlation function


    与えられた関数の形状に関する情報(鋭いとか、広がっているとか、円形からのずれの度合いなど、あるいは関数の周期性)を得るために用いられる。二つの同じ関数(あるいは図形)において、その関数に含まれるある変数の値を、二つの関数の間で相対的にずらして、二つの関数の重なりをその変数について積分した関数(あるいは図形)のこと。すなわち、対象とする関数をf、その積分変数をX、その変数の相対変位をxとすると、自己相関関数Rffは次のように書ける。Rff=∫f(X)f*(X-x)dX. ただし、*は複素共役を示す。像等の実関数の場合は、f*(X-x)=f(X-x)である。変数の相対変位xを大きくしても自己相関関数Rffが大きい場合は、オリジナルな関数(あるいは図形)は変数Xに関して広がっていることを意味する。相対変位を大きくするとRffが速く小さくなる場合は、オリジナル関数(あるいは図形)の広がりは小さい。関数が周期性を持っている場合には、あるxの整数倍ごとにRffが大きな値をとるので、その関数の周期性がわかる。このように自己相関関数を計算すれば、ある変数に関する関数や図形の形状についての知見を得ることができる。例として、電顕像では自己相関関数を計算して、像のボケから焦点ずれの度合い、像の伸びから2回非点の大きさが測定できる。自己相関関数の計算にはコンピューターでの計算の高速化を図るために、高速フーリエ変換法を利用して行う。この計算は「ある関数の自己相関関数のフーリエ変換は、関数のフーリエ変換の強度になる」という定理に基づいている。すなわち、関数のフーリエ変換を計算して、その強度を取り、その結果を逆フーリエ変換することによって自己相関関数を計算する。

    "Auto-correlation function" is a function to give information about the shape of the function such as sharpness, roundness, periodicity, etc. It is a function (or a pattern) that is acquired by integrating the product (overlap) of two same functions with respect to a variable which are shifted each other by a certain amount about the variable. That is, when we define the object function f, an integral variable of the function X and a relative shift of the function x, the auto-correlation function Rff can be written as the following equation: Rff=∫f(X)f*(X-x)dX. Note that * denotes complex conjugate. In the case of a microscope image etc., f is a real function and then f*(X-x)=f(X-x). If the value of Rff is large even for a large shift, the original function (or the original pattern) is delocalized in the X direction. Contrary, if the auto-correlation function decreases rapidly with increasing the relative shift, the original function (or the original pattern) is localized. If the function is peridic, Rff takes a large value at integral multiples of a certain x. Thus, the periodicity of the function is obtained. Therefore, the auto-correlation function enables us to obtain the knowledge about the shape of the function or the pattern with respect to the variable. For example, by calculating the auto-correlation function of a TEM image of a particle, the amount of deocus is estimated from a blur of the image and the amount of 2-fold astigmatism is obtained from an elongation of the image. For high-speed computer calculation of the auto-correlation function, FFT (fast Fourier transform) is used on the basis of the following theorem: Fourier transform of the product of certain functions is equivalent to the product of Fourier transforms of the respective functions. That is, the auto-correlation function is calculated by the inverse Fourier transform of the power of the Fourier transforms of the respective functions.

  • 磁性体

    magnetic material



    A material that is magnetized when placed in a magnetic field. "Magnetic materials" are classified into ferromagnetic material, paramagnetic material, diamagnetic material and antiferromagnetic material, from the viewpoint of how the material is magnetized.

  • 実空間

    real space



    The space in which we exist. In a TEM, the "real space" includes the space of an object to be observed and the space where an image of the object is formed (image space).

  • 実格子

    real lattice



    "Real lattice" is a set of points which have an infinitely regular arrangement in the real space and are arranged to be equivalent when viewed from every point. When a structure unit is given to each lattice point, a crystal is formed.

  • 磁場漏れ

    magnetic-field leakage



    "Magnetic-field leakage" is a phenomenon where magnetic fields are leaked in a space other than a necessary local space. The components of a TEM that consist of permanent magnets or electromagnets are designed to generate magnetic fields in a local space but magnetic-field leakage can occur.

  • 磁壁

    magnetic domain wall


  • 弱位相物体近似

    weak phase object approximation



    An approximation that is used for interpreting an HREM image. A specimen is regarded as an object that does not change the amplitude of the incident electron wave but slightly changes the phase of the wave. This approximation holds well for a very thin specimen composed of light atoms. In this case, a structure image obtained at Scherzer focus exhibits the projected potential of a crystal. When the specimen is thick, image interpretation is necessary by applying dynamical diffraction that takes account of multiple scattering.

  • 準結晶




    quasicrystal ⇒
    取得装置:JEM-ARM200F。加速電圧: 200kV。像中には、正10角形(D)、星型5角形(P)、6角形(H)の構造単位(ユニット)が存在する。Dユニットは辺を共有して準周期的に配列し、PおよびHユニットはDユニット間の隙間を埋めるように配列している。

    画像提供:東北大学 平賀名誉教授(JEOL News Vol.50,p25(2015))

    "Quasicrystal" takes a new ordered structure which has no periodicity but a long-range order with bond orientational order between the constituent atoms. Thus, the quasicrystal is totally different from amorphous. Quasicrystals have been found in many alloys composed of aluminum and two transition metals exhibiting ferromagnetic properties.

    HAADF-STEM image of an Al-Mn-Pd two-dimensional quasicrystal taken
    with a JEM-ARM200F at an accelerating voltage of 200 kV.

    In the image, decagonal (D) structure units, star-shaped pentagonal (P) units and hexagonal (H) units are clearly seen. All the D units are joined by edge-sharing linkage, and the gaps between those D units are completely filled with P units and H units. (cf. JEOL News Vol. 50, p25 (2015))

    Courtesy of the image:
    Professor Emeritus K. Hiraga, Tohoku University

  • 常磁性体

    paramagnetic material



    A material that is magnetized in the direction of a magnetic field when placed in the magnetic field, and demagnetized when the magnetic field is removed.

  • 状態密度

    density of states



    The number of electronic states per unit volume and per unit energy in energy band. The density of states (DOS) of the conduction band can be investigated by high energy resolution EELS. (The energy resolution is better than 1 eV for a TEM equipped with a thermal FEG and is about 0.3 eV for that with a cold FEG.) The DOS of the valence band is obtained by XES, which analyzes X-rays emitted from a specimen by the illumination of the incident electron beam. An energy resolution better than 1 eV is required for the analysis of the valence band. A recently-developed WDS analyzer provides an energy resolution of about 0.5 eV, giving us good DOS of the valence band.

  • 常誘電体

    paraelectric material



    "Paraelectric material" generates dielectric polarizations when an electric field is applied to the material and the material looses the polarizations when the electric field is removed. In "paraelectric materials," three kinds of polarizations exist: (1) electronic polarization, (2) ionic polarization, and (3) orientational polarization. In electronic polarization, electrons are displaced against the atomic nucleus. In ionic polarization, positive ions are displaced against negative ions. In orientational polarization, molecules having permanent dipole moments change their directions under an electric field. The paraelectric material has a small permittivity and a small dielectric loss. A material which is called quantum paraelectrics does not transform to a ferroelectric phase but remains at the paraelectric state even around absolute zero temperature due to zero-point oscillation of phonons.

  • GIF

    GIF Gatan imaging filter



    One of the post-column type energy filters produced by Gatan, which is installed behind the microscope column. This product consists of a sector analyzer of the magnetic-field type, quadrupole and octupole magnets for image enlargement, and a scintillator and CCD camera for image detection.

  • GPゾーン

    GP zone


    面状に析出した溶質原子のプレートのことで、A. Guinier(仏)とG.D.Preston(英)が独立に、X線ラウエ斑点上から延びるストリークの解析から発見した面上に析出した溶質原子のプレートのことで、発見者の名前をとりGuinier-Preston(GP) Zoneと呼ばれている。具体的には、AlやMgを主成分としCuなどの溶質原子を含む時効硬化型合金において、過飽和固溶体を急冷し低温で時効処理を行うと、平衡状態図に現れない析出物としてCuなどの溶質原子が母相の{001}面に格子整合して1~2枚の原子面として偏析する。Al, Mg合金等における時効硬化の一因となる。電子顕微鏡の明視野像では、格子歪による線状のコントラストとして観察され、高分解能像では溶質原子の並びが直接観察される。

    GP zone ⇒
    GPゾーンを含むAlCu合金の明視野像。加速電圧: 100 kV。


    "GP zone" means a plate that is composed of solute atoms segregated on a plane. The zone was discovered independently by A. Guinier and G. D. Preston through the analysis of streaks extending from X-ray Laue spots. It is named Guinier-Preston (GP) Zone after the two researchers. In the case of an age-hardened alloy that consists of Al or Mg but includes minute solute atoms (Cu, etc.), when its super-saturated solid solution is rapidly cooled and undergoes an aging treatment at a low temperature, solute atoms (Cu, etc.) are precipitated as one or two atomic planes with lattice matching on the {001} plane of the parent phase. It is noted that they do not appear as precipitates in the equilibrium state. The GP zone causes age hardening of alloys containing Al or Mg. In a bright-field image, the GP zone shows a line contrast due to lattice distortions. In a high-resolution image, the arrangement of solute atoms is directly observed.

    Bright-field image of an AlCu alloy containing GP zones taken at an accelerating voltage of 100 kV.
    GP zones (Cu precipitates) are seen to be bright (white) lines, indicated by white allows, because they do not satisfy Bragg condition.

  • ジーユーアイ

    GUI Graphical User Interface



    "GUI" is a user interface that provides intuitive operations using a computer graphics and a pointing device. Since GUI offers user-friendly operation and high visualization, it is widely used as a major interface for commercial OS. In the TEM, GUI is used to facilitate instrument operation and display of image-data. It is, however, noted that GUI is not always effective because different operations cannot be carried out simultaneously.

  • スキルミオン




    図提供: 東京大学 松元主任研究員、柴田准教授 ⇒ 

    図(a) 薄膜中のスキルミオンの磁気構造の模式図。磁気モーメントの方向を矢印で示した。磁気モーメントの方向は、一つ一つのスキルミオンの中心では薄膜に垂直で、周辺部では薄膜面内で渦巻き状に回転する。
    図(b) 微分位相コントラスト法で観察されたスキルミオンの実空間像(試料:鉄系合金)。色は、磁気ベクトルの2次元面内での方向と大きさを示している。

    Skyrmion is a vortex-like magnetic structure formed by the magnetic moments of electron spins. The term “Skymion” is named after Skyrme, a theoretical physicist of UK, who proposed the quantum structure. “Skymion” is also called “magnetic vortex” or “spin vortex”. Its size ranges from approximately several nm to 100 nm, depending on materials and chemical compositions. Skymions align like a two-dimensional crystal by cooling the specimen temperature and controlling the external magnetic field.
     Skyrmion was first observed as a real-space image by Lorentz electron microscopy. Since then, it was also imaged by STEM using the DPC (differential phase contrast) method.

    Courtesy of figures:
    Senior Researcher T. Matsumoto and Associate Professor N. Shibata
    The University of Tokyo (as of August 2015)
    Fig. (a) Schematic of the magnetic structure of skyrmions in a thin film. The directions of the magnetic moments of electron spins are indicated by arrows. The directions of those magnetic moments are perpendicular to the film plane at the core of the respective skyrmions, but swirl in the film plane at the peripheral region.
    Fig. (b) A real-space image of skymions acquired by the DPC (differential phase contrast) method (specimen: an Iron alloy). The colors in the figure depict the directions and magnitudes of the magnetic vectors in a two-dimensional plane.

  • スクロールポンプ

    scroll pump



    A dry vacuum pump that does not use oil. By rotating the scroll blade of the scroll pump, residual gasses are carried to the central part of the pump, are compressed and evacuated. Since oil is not used except a grease for the scroll shaft, the pump is oil-free and oil mist is not exhausted, which occurs for the rotary pump. The pump features low vibration and no noise. The working pressure is from 105 Pa to 1 Pa. Recently, requirements for an oil-free pump evacuation system are increasing even for the camera chamber. For such needs, a combination of the turbo-molecular pump and the scroll pump is adopted, instead of the diffusion pump.

  • スタンダードレス定量

    standardless quantitative analysis



    A system by which quantitative analysis of target elements in EDS can be conducted without using the standard specimen in each analysis. In a recent TEM, many k-factors of the Cliff-Lorimer method, which have been measured separately, are stored and tabulated in the memory of the computer on the TEM. Quantitative analysis of the elements can be performed by referring the table without measuring the standard specimen. The system or method is called "standardless quantitative analysis." In TEM, when a specimen thickness is 10 nm or less, the Cliff-Lorimer method (thin film approximation) is generally used because the absorption effect and the fluorescence excitation effect can be neglected. For example, when a specimen is composed of two elements A and B, the mass concentration ratio of element A to element B is well assumed to be proportional to the measured characteristic X-ray intensity ratio of element A to element B (proportionality factor: k). The k factor, which depends on ionization cross section, fluorescent yield, X-ray absorption by material of detector window, etc, is actually obtained from characteristic X-ray measurements of a standard specimen. It is noted that the k factor is not a constant when a specimen is thick.

  • スタンダードレス補正

    standardless correction


  • スター収差

    star aberration



    The star aberration, one of the third-order axial geometrical aberrations, is a parasitic aberration exhibiting two-fold symmetry. (Note that it is called a fourth-order aberration in terms of the wave aberration.) The star aberration cannot usually be detected due to the existence of a large spherical aberration of the objective lens, but is detected after correcting the spherical aberration of the objective lens. The star aberration appears as a pattern with a two-fold symmetry in high angle areas of a Ronchigram. In the case of a TEM equipped with a Cs corrector, prior to microscope observation, aberrations are measured and then the aberrations including the star aberration are corrected by the automatic aberration correction function with the use of the deflectors of the Cs corrector.

  • スティグマティックフォーカス

    stigmatic focus



    "Stigmatic focus" means image formation without off-axial astigmatism. For example, in the original Wien filter, focusing action occurs only in the electric field direction but does not occur in the magnetic field direction. Thus, even when an incident beam to the filter is circular, a liner beam is obtained on the image plane. To accomplish astigmatism-free imaging in the Wien filter, application of curved electric and magnetic fields produces magnetic components in the original electric field direction and thus attains the focusing action in the original magnetic field direction.

  • スティグメータ



  • ステレオ観察

    stereo microscopy



    A method that obtains stereoscopic images of a specimen. In "stereo microscopy," two electron micrographs are taken from two specimen orientations which differ in a tilt angle by 5° to 10°, and they are viewed independently with right and left eyes. When a complicated dislocation configuration is viewed, diffraction conditions for the two micrographs should be set very similar to reveal the correct three-dimensional structure.

  • ストッブス因子

    Stobb's factor



    The contrast of a high-resolution (HREM) image is lower than that expected from image simulation. "Stobb's factor" is used to adjust the simulated contrast to agree with the experimental contrast. The superposition of the background intensity due to thermal diffuse scattering (TDS) is considered to decrease the contrast of HREM images formed by elastic scattering.

  • スパッタイオンポンプ

    sputter ion pump



    A dry vacuum pump that does not use oil. In the sputter ion pump, residual gasses are ionized utilizing electric and magnetic fields. The produced ions strike a titanium cathode to sputter titanium atoms. Then, the sputtered titanium atoms form a fresh getter film (film subjected to chemical adsorption). As a result, active gasses (hydrogen, oxygen, carbon monoxide, etc.) are adsorbed to the getter film, and inert gasses (helium, etc.) are ionized and adsorbed to the cathode. The pump is used for evacuation of the electron gun chamber and the column of TEM, which require high vacuum. The working pressure is 10-4 to 10-9 Pa.

  • スピン・軌道相互作用

    spin orbit coupling


    電子のスピンsと軌道角運動量lが平行のときと反平行のときで、相互作用の大きさが違うので二つの状態は異なるエネルギー状態をとる。2p電子ではエネルギーの低いほうから順にL2 (全角運動量j = l - s = 1/2)とL3 (全角運動量j = l + s =3/2)とができる。EELSにおいて2p状態から3d非占有バンドへの遷移(Lエッジ)ではエネルギーロスの小さいほうからL3、L2の順にスペクトルが現れる。これらのスペクトルは占有状態のエネルギー分裂(数eV~20eV)を与えるものなので、EELS解析での目的である非占有状態についての情報を与えるものではない。ただL3/ L2の強度比は2:1になるはずだが非占有状態の状態密度(化学結合状態)の影響を受けて変化する。この強度比プロファイルを計算と比較すると3d電子の価数についての情報が得られる。計算にはコアホール相互作用、3d電子の電子相関、価数などを入れなければならない。L3とL2の強度比L3/L2はハイスピンのとき大きく、ロウスピンのとき小さい傾向がある。

    The magnitude of "spin orbit coupling" is different depending on whether the electron spin is parallel or anti-parallel to the orbital shell spin l, thus the two states possess different energies. In 2p electrons, L2 (total angular momentum j = l - s = 1/2) and L3 (total angular momentum j = l + s = 3/2) are formed. In an EELS spectrum of transition from the 2p occupied state to the 3d unoccupied state (band), L3 and L2 peaks sequentially appear in the energy-loss order of low to high. It should be noted that those peaks provide information on the energy splitting of the occupied state (several eV to 20 eV) but does not provide information on the unoccupied state expected by EELS. However, the intensity ratio of L3 to L2 varies from 2:1 due to the effect of the expected chemical-bonding state in the unoccupied state. When the experimental intensity profile is compared with theoretical calculations, information on the valence of 3d electrons is obtained, where the calculations must take account of the effect of core-hole interaction, correlation between 3d electrons and valences. The intensity ratio of L3 to L2 tends to be large at the high spin state whereas small at the low spin state.

  • スピン偏極電子波

    spin polarized electron



    An electron exhibits "up" state or "down" state corresponding to the quantum numbers ±1/2. Recently, a new electron gun technology using a photocathode made of a strained super lattice semiconductor enables the emission of electrons with a spin polarization of more than 90 % at room temperature. Originally, the electron source was developed for collision experiments in the field of elementary particle physics. However, due to the increase of its brightness, the source has recently been applied to photoelectron surface microscopes and transmission electron microscopes (TEM). Then, surface images and TEM images have been obtained. A TEM equipped with the gun allows us to observe the interaction between the incident electron spin and the spins and magnetic moments of the atoms in a specimen.

  • スリーウィンドウ法

    three-window method



    A method used for quantitative element (elemental) mapping by EELS. The process of the "three-window method" is as follows. Two background intensities before the inner-shell excitation of a certain element are acquired. The background intensity at the inner-shell excitation of the element is obtained by extrapolation using the two background intensities. Then, the obtained background intensity at the inner-shell excitation is subtracted from the spectral intensity of the inner-shell excitation. This method enables us to perform quantitative element mapping.

  • スリーローブ収差

    three-lobe aberration



    The three-lobe aberration, one of the fourth-order axial geometrical aberrations, is a parasitic aberration exhibiting three-fold symmetry. (Note that it is called a fifth-order aberration in terms of the wave aberration.) In addition to the three-lobe aberration, the fourth-order axial geometrical aberrations include the fourth-order coma aberration and the five-fold astigmatism. In the aberrations exhibiting three-fold symmetry, there is the three-fold astigmatism which is the second-order axial geometrical aberration and a low order aberration compared to the three-lobe aberration. In a two-stage hexapole Cs corrector, even when the three-fold astigmatism is corrected, a Ronchigram sometimes exhibits a three-fold symmetry pattern at its high angle areas. This pattern can be due to the residual three-lobe aberration.

  • スルーフォーカス法

    through-focus method



    The "through-focus method" is an imaging method used in observation of lattice images or crystal structure images. It acquires the images through gradual change of the focus so that an optimum image can be obtained.

  • スロースキャンCCDカメラ

    slow-scan CCD camera


    走査速度を遅くすることで,通常のCCD TVカメラよりS/Nを上げて良い画像を得る方式のカメラ。通常のテレビレートは1/30s/1フレームであるが、スロースキャンCCDカメラの撮影モードでは1~2s/1フレーム、観察モードでは~0.1s/1フレームで使用される。

    A CCD camera, whose scan speed is slower than that of a normal CCD TV camera to acquire a higher-quality image with a higher signal-to-noise ratio. A normal TV scan rate is 1/30 s per frame but the scan rate of the "slow-scan CCD camera" is 1 to 2 s per frame in the photography mode and ~0.1 s per frame in the observation mode.

  • 制限視野回折

    SAD selected-area diffraction


    入射電子線を平行にして試料に照射し、点状の斑点からなる回折図形を得て、結晶構造の定性的な解析をする手法。対物レンズの像面に制限視野絞りを入れることにより、回折図形を得る試料の場所(直径 数100nm)を選ぶことができる。この方法により、特定の場所の格子定数、格子型、結晶方位を知ることができる。

    selected area diffraction⇒
    対物レンズ (OL) と4段結像レンズ系(中間レンズ(IL1, IL2, IL3) および投影レンズ (PL) )で構成される一般的な結像光学系の概略。

    (a)結像レンズ系の焦点を、対物レンズで作られる試料の像に合わせて試料の拡大像を観察する像観察モードで制限視野絞り(Selected Area Aperture : SA絞り)を入れ、視野が選択された状態を示す。


    A method for qualitative analysis of crystal structures from a spot diffraction pattern, acquired by illumination of a parallel electron beam on a specimen. By inserting a selector (selected-area) aperture into the image plane of the objective lens, a diffraction pattern is obtained from a specimen area of a several 100 nm diameter. The method enables us to determine the lattice parameters, lattice type and crystallographic orientation of the selected area.

    Overview of the standard optical ray diagram of the imaging lens system which is composed of the objective lens (OL) and the four-stage imaging lens system (intermediate lenses (IL1, IL2, IL3) and projector lens (PL)).

    (a)Image observation mode, in which the magnified image of a specimen is observed on the screen by focusing the imaging lens to the image formed by the objective lens.
    In this mode, the selected-area aperture (SA) is inserted into the image plane of the objective lens so that an observation area (field of view) is selected.

    (b)Diffraction pattern observation mode, in which the diffraction pattern of a specimen is observed on the screen by focusing the imaging lens to the back focal plane of the objective lens. By switching from the imaging mode to the diffraction mode, the diffraction pattern formed only from the selected area in step (a) is obtained.


  • 制限視野絞り(中間レンズ絞り)

    selected-area aperture (intermediate-lens aperture)


    制限視野回折を行なう際、回折図形を得る試料の領域を制限する絞り。対物レンズの像面(中間レンズの物面)に挿入される。絞りの直径は通常 10~100μm。

    An aperture for selecting a specimen area in the selected area diffraction (SAD) mode. The aperture is inserted into the image plane of the objective lens (or object plane of the intermediate lens). The aperture diameter ranges normally from 10 μm to 100 μm.

  • 静電ポテンシャル

    electrostatic potential



    An electrostatic field is produced by static charge distributions. The electrostatic potential is the potential of the electric field, which is produced by charge distributions. Or the electric field is given by the space derivative of the electrostatic potential. The Fourier transform of the electrostatic potential that is created by the nucleus and orbital electrons of an atom gives the atom form factor.

  • 静電レンズ

    electrostatic lens



    A lens that converges electron beams by an electrostatic field. Since the "electrostatic lens" has larger aberration than the magnetic field lens, the former lens is not used for imaging but used for acceleration and deceleration of the electron beams.

  • 制動放射




    "Bremsstrahlung" is an electromagnetic-wave radiation that is produced when an electron is rapidly decelerated by the Coulomb field of an atomic nucleus at a collision event of the electron with the atomic nucleus. Bremsstrahlung forms the background in an EDS spectrum.

  • 成膜




    "Deposition" is to form a thin film on a solid surface by physical sputtering, chemical vapor deposition, etc.

  • 析出物




    "Precipitate" is a solid formed as a new stable phase separated from the matrix crystal by atoms excessively dissolved in a supersaturated solid solution. When the degree of supersaturation of the dissolved atoms is low, they do not form a phase but are collected on grain boundaries or dislocations.

  • 積層欠陥

    stacking fault



    A kind of planar lattice defect (planar fault). When considering a perfect crystal to be produced by periodic stacking of (different kinds of) atomic planes, "stacking fault" means a fault where the order is violated.

  • セクター型分光器

    sector analyzer



    One of the post-column type energy filters, which is installed behind the column of a TEM. Since the magnet of the analyzer is sector-shaped, this analyzer is called "sector analyzer." Its energy dispersion is 4 to 5 μm/eV for a 200 kV electron beam.

  • 繊維図形

    fiber pattern



    A "fiber pattern" is a diffraction pattern produced from fiber structures in which molecules are oriented regularly only along one axis. The diffraction pattern with the fiber-axis incidence forms Debye-Scherrer rings. As the incidence direction is tilted from the fiber axis, the ring-shaped intensity distributions on the successive Laue zones intersect with the Ewald sphere. A distorted arc diffraction pattern or a fiber pattern appears.

  • 遷移放射

    transition radiation



    When a relativistic charged particle passes from a substance to another with different dielectric permittivities (from vacuum to a substance), electric dipoles are induced on the interface of the substances. At this event, radiation is emitted because the magnitude of the dipole changes with time. This phenomenon is called "transition radiation" and is observed strongly for metals and semiconductors. The emission intensity of the radiation (light) is approximately proportional to the square of the electronic polarizability of the substance.

  • 選択則

    selection rule


    EELSにおいてクーロン相互作用によるバンド間遷移を考えるとき、小角散乱のみを考慮すると(小角散乱近似)、バンド間遷移を与える相互作用は双極子だけになる(双極子近似)。すなわち、軌道角運動量の変化が⊿l = ±1の遷移のみが許される。このように遷移が選択的に起こる規則をいう。したがって1s殻からの励起では非占有状態の2p、3pなどのp状態への遷移がおきる。したがってELNESでは非占有バンドの全状態密度でなく、部分状態密度が分かることになる。価電子励起のような低エネルギー損失領域では大きな角度の散乱も可能で選択則を破る遷移も起こる。

    In EELS, when interband transitions due to Coulomb interactions are considered, if only small-angle scattering is taken into account (small-angle scattering approximation), interband transitions are limited only to the dipole transition (dipole approximation). That is, only the transitions with the change of an angular orbital momentum being ⊿l = ±1 is allowed. The rule which clarifies the allowed and forbidden transitions is called "selection rule." Thus, the transitions from the 1s shell to the unoccupied p states (2p, 3p, etc.) occur. In ELNES, partial density of unoccupied states, instead of total density of states, is obtained. In the low energy-loss region corresponding to valence-electron excitations, scattering at large angles is allowed and this can give rise to transitions in which the selection rule does not hold.

  • 線分析

    line analysis



    In spectroscopic analysis, "line analysis" is to acquire a spectrum from a line scan of an electron beam on a specimen.

  • 占有状態

    occupied state



    In the occupied state in a molecule or crystal, the certain energy level and band are occupied by (valence) electrons. These electrons cannot move freely.

  • ゼルニケ位相コントラスト

    Zernike phase contrast



    Zernike phase contrast⇒図1

    (a) Conventional TEM (C-TEM) 像 (b) Zernike phase contrast (ZPC-TEM) 像。加速電圧:200kV。試料:氷包埋された T4 ファージ。 (c) T4 ファージの模式図。

    ZPC-TEM 像では、C-TEM像に比べて、カプシド(Capsid)内部のDNAの微細構造、カプシド表面にある毛状構造物、筒状構造等が、より高いコントラストで観察されている。

    In TEM, "Zernike phase contrast" means contrast which is obtained by converting the phase change of electron waves scattered by a specimen into the amplitude change. The conversion is performed by using a phase plate or a combined effect of the spherical aberration of the electron lens and defocus.

    Zernike phase contrast

    (a) Conventional TEM (C-TEM) image.
    (b) Zernike phase contrast (ZPC-TEM) image of an ice-embedded T4 phage taken at an accelerating voltage of 200 kV.
    (c) Schematic of T4 phage.

    Compared with the C-TEM image, the ZPC-TEM image clearly visualizes the fine structures of DNA in a capsid, the hair-like structural objects and the cylindrical structures on the capsid surface.

  • ゼロ次ラウエ帯反射

    zeroth-order Laue zone (ZOLZ) reflection



    "Laue zones" are defined as the reciprocal lattice planes perpendicular to the direction of the incident beam. A Laue zone containing the point of origin (reciprocal lattice point corresponding to the incidence point) is called the "zeroth-order Laue zone (ZOLZ)." The ZOLZ reflections appear around the transmitted beam in a CBED pattern, which have symmetry characteristic of a specimen crystal and show loose angular change. The ZOLZ reflections give two-dimensional information on a crystal projected along the direction of the incident beam.

  • ゼロ・ロスピーク

    zero-loss peak



    A sharp peak with an energy loss of 0 (zero) appearing in an EELS spectrum. The "zero-loss peak" is composed of no-scattered electrons and elastically scattered electrons. In a real spectrum, the peak shows an energy broadening (less than 0.7 eV) due to the energy spread of the incident beam. In the analysis of low-loss EELS spectra to obtain a dielectric function, it is important to precisely subtract the tail of the zero-loss peak.

  • 前固定




    Prefixation is the first-step fixation technique of chemical fixation for biological specimens observed with a TEM.  This technique aims at inactivation and preservation of proteins.  In the preparation of a biological specimen for TEM observation, dehydration and resin embedding are applied.  Under these procedures, a robust fixation of the fine structures of biological tissues is required.  For such a fixation, it is effective to use strong oxidizing reagents (osmium tetroxide, potassium permanganate, etc.).  However, these reagents have disadvantages that include slow permeation into the specimen and destruction of proteins in the specimen.  To avoid these disadvantageous phenomena, the specimen is pre-fixed with paraformaldehyde or glutaraldehyde, which permeate quickly the specimen and cross-links the proteins to preserve the original morphologies.

  • 前方磁界

    pre-magnetic field



    In a modern electron microscope, a specimen is placed in the objective lens. The magnetic field produced above the specimen (at the condenser lens side) is called "pre-magnetic field."

  • 相関法

    correlation method



    In three-dimensional tomography, the "correlation method" takes the correlation between each image and performs positional adjustment of these images so that the correlation becomes maximum.

  • 双極子近似

    dipole approximation


  • 相互相関関数

    cross-correlation function


    二つの関数がどの程度似ているか、あるいはどの程度ずれているかを表すために用いられる関数。二つの異なる関数(あるいは図形)において、それらの関数に含まれるある変数の値を、二つの関数の間で相対的にずらして、それらの関数の重なりをその変数について積分した関数(あるいは図形)のこと。すなわち、対象とする関数をf、g、それらの積分変数をX、二つの関数の間でのその変数の相対変位をxとすると、相互相関関数Rfgは次のように書ける。Rfg=∫f(X)g*(X-x)dX. ただし、*は複素共役を示す。像等の実関数の場合は、g*(X-x)=g(X-x)である。対象となる二つの関数が同じ場合、相互相関関数は自己相関関数になる。Rfgの値が大きい場合は、二つの関数(あるいは図形)が似ていることを示している。また、ある特定のxについてRfgが大きくなる場合は、二つの関数の相対的なずれの量がわかる。例として、電顕像を二回撮影し、二つの像の間の相互相関関数を計算すると(この場合、xは時間の関数x(t))、撮影の間に像がどれだけドリフトしたかに関する知見を求めることができる。(xが小さいところで相関関数の値が大きければ、ドリフトが少ない。) 相互相関関数の計算にはコンピューターでの計算の高速化を図るために、高速フーリエ変換法を利用して行う。この計算は「相互相関関数のフーリエ変換は、それぞれの関数のフーリエ変換の強度になる」という定理に基づいている。すなわち、相互相関関数を構成する各関数のフーリエ変換を計算して、それらの強度を取り、その結果を逆フーリエ変換することによって相互相関関数を計算する。

    "Cross-correlation function" is a function expressing to what extent arbitrary two functions are similar or to what extent the two functions are shifted. It is a function (or a pattern) that is acquired by integrating the product (overlap) of arbitrary two functions with respect to a variable which are shifted by a certain amount about the variable. That is, when we define the object functions f, g, an integral variable of the functions X and a relative shift of the two functions x, the cross-correlation function Rfg can be written as the following equation: Rfg=∫f(X)g*(X-x)dX. Note that * denotes complex conjugate. In the case of a microscope image, etc., the functions f and g are real, and then g*(X-x)=g(X-x). If the two object functions are the same, the cross-correlation function is reduced to the auto-correlation function. If the value of Rfg is large, it indicates that the two functions (or patterns) are similar to each other. If Rfg takes a large value for a certain value of x, the relative shift between the two functions is obtained. For example, when the cross-correlation function is calculated for two TEM images taken successively, it gives the knowledge about the image drift during the acquisition of the images. (If the value of the correlation function is large for a small value of x, this indicates a small image drift.) For high-speed computer calculation of the cross-correlation function, FFT (fast Fourier transform) is used on the basis of the following theorem: Fourier transform of the product of certain functions is equivalent to the product of Fourier transforms of the respective functions. That is, the cross-correlation function is calculated by the inverse Fourier transform of the power of the Fourier transforms of the respective functions.

  • 走査コイル

    scanning coil



    Electromagnetic coil(s) used to scan a target area with an electron beam.

  • 走査低エネルギー電子顕微鏡

    SLEEM scanning low energy electron microscope



    A "SLEEM (scanning low energy electron microscope)" is an instrument to form a surface image, in which the SLEEM image is obtained as follows. An incident electron beam with an energy of several 10 V to several 100 V is used. A small-sized focused electron probe is scanned over the surface of the specimen. Scattered electrons and secondary electrons from the specimen are detected by a SEM detector. To obtain surface information, the specimen area is kept at ultra high vacuum. The SLEEM instrument is usually made by modifying a SEM instrument, thus the beam scan system and secondary electron detector for the SEM instrument are used for the SLEEM instrument. Applying a negative voltage to the specimen gives rise to the formation of a cathode lens or a retarding electric field near the specimen. By varying the value of the negative voltage, the energy of the incident electron beam is varied. A high image resolution is attained at a low incident energy. The present SLEEM achieves a resolution of 10 nm at an incident energy of 10 eV.

  • 走査電子顕微鏡

    SEM scanning electron microscope



    An electron microscope in which a small electron probe is scanned over the surface of a bulk specimen, and secondary or backscattered electrons emitted from the surface are collected by a detector, and finally, the intensity of the detected signal is displayed on a computer monitor screen as a series of bright spots synchronized with the scan of the electron probe. An image formed by secondary electrons enables us to observe the fine structure or morphology of the surface of the bulk specimen, whereas an image formed by backscattered electrons provides the difference in the composition of the specimen. The "scanning electron microscope (SEM)" is used by adding various analytical functions (tools) such as EDS and WDS. An important factor that determines the SEM resolution is the size of the incident electron probe (beam) on the specimen. To decrease the probe size, the most essential point is to decrease the size of the electron (emission) source. The cold cathode FEG has the smallest source size, followed by the Schottky FEG, the LaB6 (tip) electron gun, and the tungsten (filament) electron gun. The second most essential point that determines the probe size is the selection of the objective lens. Three types of objective lenses are available; (1) out-lens type, (2) snorkel lens type, and (3) in-lens type. In the out-lens type, a specimen is placed below the objective lens allowing tilting a large specimen. In this lens, limitation on specimen size is not severe but the production of a small beam is difficult because the focal length of the lens becomes large. In the in-lens type, a specimen is inserted into the objective lens in the same manner as the TEM. In this lens, a small probe can be produced because the focal length can be made small. However, the specimen size is limited to several mm. The snorkel lens has a compromise design between the out-lens and in-lens. (The term, "snorkel," originates from the fact that the lens geometry resembles a snorkel used by divers.) A specimen is placed below (not far from) the objective lens. Thus, a relatively small probe can be produced and also a relatively large specimen can be treated. The SEM resolution is degraded at low accelerating voltages due to the chromatic aberration effect. Normally, the resolution is defined at 20 to 30 kV. An ultra-high resolution SEM achieves a resolution of about 1 nm, whereas a general-purpose SEM provides a resolution of about 10 nm. The use of a Cs corrector or a Cc corrector enables a further decrease of the incident-beam size, but causes a disadvantage of a short focal depth because the acceptance angle becomes larger. As the accelerating voltage of the incident electrons is decreased, the penetration depth of the electrons becomes smaller. This reduces a spread of secondary electrons generated by backscattered electrons in the specimen, thus enhancing the image contrast. Advantages of low accelerating voltage include the reduction of the background in the image, the decrease of charging, and the decrease of damage to the specimen. In SEM, charging degrades the image quality. If the current of the incident electrons exceeds the current of electrons flowing out of the specimen, charging takes place. The charging disturbs the image, sometime forming nothing like the true image. When a nonconductive specimen is used, to prevent charging, the specimen is coated with a conductive material, such as noble metal, Al and C. In a low-vacuum SEM, a nonconductive specimen may be observed without coating.

  • 走査透過電子顕微鏡像(ステム像)

    STEM image scanning transmission electron microscope (STEM) image



    "Scanning transmission electron microscope (STEM) image" is obtained as follows. A small-sized, focused electron probe is scanned over a thin specimen using the double-deflection system. The intensity of the transmitted wave (or the diffracted wave) exiting from a point on the specimen is detected with an annular detector. Then, the intensities are displayed on a computer monitor as a series of bright spots in synchronism with the scanning electron-probe. The resolution of the STEM image is determined by the probe diameter. The STEM method has two observation modes; bright-field mode and dark-field mode.

  • 双晶




    When two adjacent crystals are symmetric with each other about a specific plane or a specific axis, these two crystals are called "twins."

  • 相対論補正

    relativistic correction



    Relativistic correction is a correction to take in the relativistic effect arising when the velocity of an electron becomes high to an extent which cannot be neglected compared with the velocity of light. In the field of electron microscopy, the relativistic effect due to increase of the mass or decrease of de Broglie wavelength is taken into account by replacing the accelerating voltage with the corrected accelerating voltage. That is, the accelerating voltage after the relativistic correction E* [V] is calculated by the following equation for a given (before relativistic correction) accelerating voltage E [V], here, m0 is the rest mass of an electron, e the elementary charge of an electron, and c the velocity of light.
    相対論補正 relativistic correction

  • 相転移

    phase transformation



    A phenomenon where a substance transforms to a different state by a change of the external conditions (temperature, pressure, magnetic field, etc.). "Phase transformation" is classified into the first-order and the second-order phase transformations. The former exhibits a discontinuity in the first derivative of the free energy with respect to temperature, which includes melting of solids and vaporization of liquids. The latter exhibits a discontinuity in the second derivative of the free energy temperature, which includes the transformation of the ferromagnetic state (iron, etc.) to the paramagnetic state at Curie temperature and the transformation of the alloys from a chemical order state to a disorder state (and vice versa).

  • 阻止能

    stopping power



    "Stopping power" means the average amount of energy loss per unit distance when a charged particle passes through a substance. In the case of TEM, the energy loss occurs mainly due to ionization and excitation of electrons. The "stopping power" is used for calculation of the temperature increase of specimen and the degree of specimen damage.

  • 損失関数

    loss function



    "Loss function" is given by the negative of the imaginary part of inverse of the dielectric function or Im[‐1/ε(ω)], where ε(ω) is the dielectric function. By removing the effect of multiple scatterings from an EELS spectrum, the EELS spectrum only due to single scattering is obtained. Next, the effect of the incident beam intensity and that of the aperture size from the spectrum are removed. And then, when the intensity of the obtained spectrum is normalized, the absolute value of the electron energy loss or the loss function is obtained. The loss function is the most important quantity obtained from EELS. By using Kramers-Kronig equation, the real part corresponding to the loss function is derived. From the real and imaginary parts, the dielectric function of the specimen is calculated. Various physical properties such as refractive index, optical reflectivity, optical absorption intensity etc. can be calculated from the dielectric function.

  • 像回転

    image rotation



    A phenomenon of an image rotation when the magnification is changed in a TEM, which is inconvenient for image observation. The second and third parts of the intermediate lens system that have opposite excitations to each other are designed to cancel or to minimize the image rotation.

  • 大気にする(開放して)




    "Venting" is to make the pressure in the vacuum chamber to atmospheric pressure. In venting, air or nitrogen gas is used. (The latter case is used to prevent the entering of moistures in the chamber.)

  • タイコグラフィー



    入射電子プローブを、その照射領域の一部が重なるよう試料上で二次元スキャンして各走査点において回折図形を取得し、回折図形の強度から試料の構造を再構成する方法。Ptychoはギリシャ語で重なり (fold) を意味する。X線構造解析の分野で実用的に使われている。
    透過電子顕微鏡においては、装置の安定性向上と収差補正装置の開発とともに、回折図形の二次元デジタル画像を高速に取得できる高速高感度カメラの登場によって、より精度の高いデータ取得が可能となったことから、2012年頃から原子分解能の構造像を得る (位相回復) 手法の一つとして注目されてきた。特に近年の研究で、ノイズが少なくコントラストの高い構造像 (図2) が得られることが報告され、関心を集めている。透過電子顕微鏡では、以下の二つの方法のタイコグラフィーが現在行われている。

    1) 入射電子線を試料上でデフォーカスして照射した状態で走査する方法 (図(a))
    デフォーカスして照射領域を大きくした入射電子線を用いて、照射領域の一部が重なるように走査する。走査点数は、照射領域とプローブサイズに応じて数10点 ×数10点以下である。タイコグラフィーにより構造像 (位相回復像) を得る計算は以下のようにして行う。
    試料の初期関数を1と仮定し、プローブ関数として箱型関数を仮定する。試料の出射波関数 (試料関数とプローブ関数の積) をフーリエ変換して回折図形を得る。この回折図形の強度を実験で取得した回折図形の強度と置き換える。更新された回折図形を逆フーリエ変換して実空間の像(構造像)に戻す。この操作によりこの試料位置での出射波関数が更新される。プローブ関数を正しい関数 (初期に与えた関数) に置き換え、この計算を繰り返す。その後、次のプローブ位置に移動して、同様の計算を実行する。このようなプロセスを順番に行い、計算による回折図形と実験で得た回折図形の差分が十分に小さくなるまで繰り返す。
    このようにして得られた試料の構造像 (位相像) を図(c)に示す。本手法は従来のインコヒーレントなディフラクティブイメージングと類似しているが、隣り合う照射領域の重なり部分で試料関数が一致することが拘束条件に加わっているために、ディフラクティブイメージングで起きている解の一意性の問題は克服されている。さらに観察領域も走査することによって制限されなくなっている。
    2) 入射電子線を試料上にフォーカスして照射した状態で走査する方法 (図(b))
    試料上にフォーカスした電子線を用いて収束電子回折図形を二次元画像として取得する。その電子線を試料上で二次元的に走査する。通常、走査点は数万点を超え、取得したデータは四次元 (二次元走査+二次元回折図形) の大量のデータとなる。
    まず、[二次元走査R+二次元回折図形K]の四次元データRKを、二次元走査に関する部分Rについてフーリエ変換して [二次元周波数Q+二次元回折図形K]の四次元データQKを得る。ある空間周波数qに対する回折図形Kの中の "透過波と回折波との干渉領域 (K')" には、構造のフーリエ成分q-が強度として表れている (図(b)下部)。次に、得られる構造像(位相像)のS/N比を改善するために、干渉領域 (K') 外の強度の振幅をゼロにする。さらに、透過波に対して対称に位置する回折波と透過波との干渉領域(K'') の強度の符号 (位相)を反転させ、干渉領域 (K') の強度と同位相にする。この操作によって、積分時に通常はK'とK''で相殺されてしてしまう信号を足し合わせて強度を増強できる。引き続いて、QK中の周波数成分q毎に二次元回折図形 (図(b)下部) K' とK'' の強度を積分し、二次元空間周波数図形Q' をつくる。最後に、Q’ を逆フーリエ変換して、試料(実空間)の構造像(位相像)を得る(図(d))。

    (校閲 Dr. Peng Wang、南京大学)

    (a)電子線の照射領域の一部が重なるようにして走査するタイコグラフィー。照射領域は数nm~数10nm程度で、走査点数は通常、数10点 ×数10点以下である。
    (b)電子プローブ(0.3nm程度以下)を試料上にフォーカスして走査するタイコグラフィー。走査点数は通常のSTEMと同様に数100点 × 数100点程度。回折図形の取得には、高速高感度カメラ(ピクセル型STEM検出器)が用いられている。
    (c) (a)の手法により再構成した単層MoS2の位相像(構造像)。(データ提供:Dr. Peng Wang 南京大学)
    (d) (b)の手法により再構成した単層グラフェンの位相像(構造像)。

    (a) 四次元データより再構成されたグラフェンの構造像。ここでは原子位置を明るく表示している。
    (b) 四次元データと同時取得された通常のADF像。

    Ptychography is a method to reconstruct the crystal structure (image) of a specimen from the diffraction patterns obtained from each point (area) scanned over a specimen using a convergent probe so that a part of the illuminated area overlaps. “Ptycho” means “fold” in Greek. This method has been used in X-ray crystal structural analysis.
    Ptychography for Electron Microscopy has attracted attention as one of the method to obtain the structural image (phase recovery) of atomic resolution since about 2012, owing to the advent of a high-speed and high-sensitivity camera that achieves fast acquisition of a two-dimensional (2D) digital image, together with improvement of microscope stability and advancement of the aberration corrector. In particular, it has been reported in recent electron ptychography studies that low-noise and high-contrast structure images are obtained, thus gaining increased attention. In transmission electron microscopy, the following two types of ptycography methods are being conducted.

    1) Method to scan a specimen with a defocused convergent electron probe (Fig. (a))
    A specimen is illuminated with a defocused convergent electron probe to broaden the illumination area. The probe is scanned on the specimen so that the adjacent illumination areas are partially overlapped to each other. The scan points of the probe are normally a few 10 points × a few 10 points or less depending on the scanning area and probe size. The procedure to obtain a structure image (phase image) by means of this type of ptychography is as follows:
    The initial specimen function is assumed equal to 1 and the probe function is assumed to be a box function. The specimen exit-wave function (a product of the specimen and probe functions) is Fourier-transformed to obtain a diffraction pattern, the intensities of which are replaced by those of the pattern acquired experimentally. The updated diffraction pattern is then transformed back to an image in the real space by an inverse Fourier transform, which gives a new revised exit-wave function for this probe position. The probe function obtained is replaced with the correct function or the original one. And the above procedure is repeated. Then, the calculation moves to the next position. Aforementioned procedure is repeated until the difference of the calculated and experimental diffraction patterns becomes sufficiently small.
    The resultant structural image (phase image) of the specimen is shown in Fig. (c). The present method is similar to conventional incoherent diffractive imaging. It should be however noted that non-unique solution problem arising in diffractive imaging is overcome due to the additional constraint, in which the specimen function in the overlapping region of the adjacent illumination areas have to be the same in the calculation for the diffraction patterns recorded. Furthermore, the issue of a limited field of view is cleared by scanning technique.
    2) Method to scan a specimen with a focused convergent electron probe (Fig. (b))
    A specimen is illuminated with a focused convergent electron probe.The convergent beam electron diffraction (CBED) pattern is recorded as a 2D image. The probe is scanned two dimensionally on the specimen. Scan points of the probe becomes a huge four-dimensional (4D) data set (2D CBED patterns +2D scan points), normally exceeding a few 10 thousands points.
    The procedure for reconstructing a high-contrast structure image is as follows. First, the 4D data set RK (2D scan points R + 2D CBED patterns K) is Fourier-transformed with respect to the 2D scan points R to obtain another 4D data set QK (2D spatial frequencies Q + 2D CBED patterns K). In the overlapping area (K’) of the transmitted disc and a neighboring diffracted disc of the CBED pattern for a certain 2D spatial frequency q, the intensity of the Fourier component q of the structure appears (bottom of Fig. (b)). To improve the signal-to-noise ratio of the structure image (phase image) to be obtained, the intensities outside the interference area (K’) are set to be 0 (zero). And the sign (phase) of the intensities in the interference area (K'') located symmetrically with respect to the transmitted disc is reversed. By this processing, the intensities of the two areas (K’ and K''), which are normally canceled out when integrating, can be added positively or enhanced. Then, the intensities of the two areas (K’ and K'') of the 2D CBED pattern (bottom of Fig. (b)) are integrated for each spatial frequency component q of the 4D data set QK, so that a 2D spatial frequency pattern Q' is created. Finally, this 2D spatial frequency pattern Q' is inverse-Fourier transformed to obtain the structure image (phase image) of the specimen (Fig. (d)).

    (Proofread by Dr. Peng Wang, Nanjing University)

    Fig. 1
    (a) Ptychography in which a specimen is scanned with a defocused convergent electron probe so that adjacent illumination areas are partially overlapped to each other. The illumination area is about a few nm to a few 10 nm in diameter. The number of the scan points is normally a few 10 times a few 10 or less.
    (b) Ptychography in which a specimen is scanned with a focused convergent electron probe (probe diameter: about 0.3 nm or less). The number of the scan points is a few 100 times a few 100 (the total number exceeding a few 10 thousands) like the case of ordinary STEM. A high-speed and high-sensitivity camera (pixelated STEM detector) is used to obtain a series of the CBED patterns.
    (c) Structure image (Phase image) of a mono-layer of MoS2 reconstructed by the defocus method (a). (Data courtesy: Dr. Peng Wang, Nanjing University)
    (d) Structure image (Phase image) of a mono-layer graphene reconstructed by the focus method (b).

    Fig. 2 Comparison of a reconstructed structure image (phase) obtained by Ptychography in which a specimen is scanned with a convergent probe and a simultaneously-obtained ABF image of a mono-layer graphene acquired at an accelerating voltage of 200 kV.
    (a) Structure image (phase) of graphene reconstructed from 4D data set. Here, the atomic sites appear bright.
    (b) Ordinal ADF image simultaneously acquired with the 4D data set.
    Comparison of the two images elucidates that the reconstructed structure image (phase) has a higher signal-to-noise ratio and provides higher contrast than those of the ADF image.

  • 体積プラズモン

    volume plasmon





    ここで、ωpはプラズマ振動の角振動数。ħ= ⁄ 2πはプランク定数、eは電子の素電荷、mは電子の質量、Nは自由電子の密度を表す。プラズモンエネルギーは金属内自由電子の密度の平方根に比例する。

    (a) 自由電子によるプラズモンの模式図。金属内では、原子核および内殻電子からなる正イオンと自由電子が一様に分布し、全体として電気的に中性の状態にある。そこに外から高速電子が入射すると、そのクーロン力によって自由電子に疎密が生じ、プラスとマイナスの電荷領域が現れる(図1(a)中+と-の領域)。その結果、電場が誘起され(青矢印)、その電場を駆動力として自由電子の集団は固有振動(プラズマ振動)をする。(b)束縛電子によるプラズモンの模式図。赤い点は正イオン、青い丸は価電子を表す。入射電子のクーロン力によって束縛電子(価電子)が変位し、価電子の集団がプラズマ振動をする。図1(b)の上方の矢印は価電子の変位による分極を表す。

    Alの自由電子密度はN=1.8×1023 e/cm3である。プラズモンエネルギーは15.7eVと計算され、実験値の15.0eVと良く一致する。LiやNaなどの一価金属でも計算値と実測値は良い一致を示す。
    絶縁体であるダイヤモンドでは、価電子密度N=7.0×1023 e/cm3から求められるプラズモンエネルギーは31eVであり、実験値の34eVと比較的良い一致を示す。LiFやNaClなどのイオン結晶でも、価電子密度から計算したプラズモンエネルギーは実験値をよく再現する。表1に、いろいろな物質に対するプラズモンエネルギーを示す。
    ただし、計算で予想されるプラズモンエネルギーと近いエネルギーにバンド間遷移が強く起きる物質では、プラズモンエネルギーが予想値からは大きくずれることがある。銀のプラズモンの場合では、自由電子密度N=0.59×1023 e/cm3から予想されるプラズモンエネルギーは9.0eVである。

    Table1. Plasmon energies for several materials

    (東北大学 佐藤庸平准教授による)

    Plasmon peaks of Al, Si and Diamond in EELS spectra

    Collective oscillations of free electrons with a longitudinal wave or compressional-wave, which are induced in metals by an electron beam or a charged-particle, are called "volume plasmon". The volume plasmon is excited also in semiconductors and insulators. Its oscillation energy (plasmon energy) is proportional to the square root of the free electron density (valence electron density for semiconductors and insulators). The volume plasmon is directly observed as a peak in an electron energy-loss spectrum. It should be noted that the volume plasmon cannot be excited nor can be observed with a light wave or a transverse wave.

    When a high-speed electron beam is incident on a solid metal, the Coulomb force formed by the beam induces a density change (compression) in the homogeneously distributed free electrons in the metal. With the induced Coulomb force as a driving force, a longitudinal oscillation wave of the free electrons with a specific frequency is created (see Fig.1). Quantization of this collective motion of the free electrons is called volume plasmon. The energy of the volume plasmon, EP, is expressed by the following equation.

    Here, ωp is the angular frequency of the plasma oscillation. ħ= h/2π is Planck’s constant. e, m, and N respectively express the elementary charge of an electron, the mass of an electron, and the density of the free electrons. The plasmon energy is proportional to the square root of the free electron density in a metal.
    Although the volume plasmon is originally considered for free electrons, it is excited also in semiconductors and insulators as a collective oscillation of the whole valence electrons. The valence electrons vibrate collectively against positive ion cores. The energy or frequency of the plasmon is calculated by substituting the density of the valence electrons into the above equation.

    Fig. 1(a) Scematic of plasmon induced by free electrons. Metal is electrically nutral because free electrons and positive ions consisting of an atomic nuclei and inner shell electrons are homogenously distributed. When a high energy electron beam is incident on a metal from outside, the Coulomb force of the incident beam creates a density change in the free electrons, or positive and negative charged regions (indicated by (+) and (-) in Fig. 1(a)). With the electric field (indicated by blue arrows) caused by the density change as a driving force, the free electrons collectively starts a characteristic oscillation (plasma oscillation). (b) Schematic of plasmons of bounded electrons. Red dots and blue circles respectively show positive ions and valence electrons. The bounded valence electrons are displaced by the Coulomb force of the incident electron beam, density changes of the valence electrons being created. Then, the valence electrons collectively oscillate with plasma frequency. Black arrows at the top of Fig. 1(b) represent polarization caused by the displacements of the valence electrons. Plasma vibration of the bounded electrons is a longitudinal wave vibration caused by polarization of the atoms.

    The charge density of Al is N = 1.8 × 1023 e/cm3. The plasmon energy is calculated to be 15.7 eV, showing a good agreement with an experimental value of 15.0 eV. For monovalent metals (Li, Na, etc.), the calculated energies agree well with the energies experimentally obtained.
    For diamond (insulator), the plasmon energy is calculated to be 31 eV using the valence electron density (N = 7.0 × 1023 e/cm3), showing a rather good agreement with an experimental energy of 34 eV. In the cases of ionic crystals such as LiF, NaCl etc., their plasmon energies calculated using the valence electron densities well reproduce the energies experimentally obtained. Table 1 shows the plasmon energies for various materials.
    However, for a material in which interband transitions strongly occur close to the expected plasmon energy, the experimental plasmon energy can be largely deviated from the expected energy. For example, in the case of Ag, the plasmon energy expected from the valence electron density of N=0.59×1023 e/cm3 is 9.0 eV but the experimental plasmon energy is observed at 3.9 eV due to a strong interband transition of the d orbital electrons at 4.0 eV.

    Table1. Plasmon energies for several materials

    Materials Valence electron density [e/cm3] Ep [eV] (Calculation) Ep [eV] (Experiment)
    Li 0.47 × 1023 8.0 7.1 [1]
    Na 0.27 × 1023 6.1 5.7 [1]
    Al 1.8 × 1023 15.7 15.0
    Ag 0.59 × 1023 9.0 3.9
    Si 2.0 × 1023 16.5 16.7
    GaAs 1.8 × 1023 15.7 15.9
    Diamond 7.0 × 1023 31 34
    LiF 4.9 × 1023 25.9 25.3 [1]
    NaCl 1.8 × 1023 15.7 15.5 [1]

    [1] H. Raether (1980) "Excitation of Plasmons and Interband Transitions by Electrons" Springer Tracts in Modern Physics, Vol. 88, Springer-Verlag. New York.

    Plasmon is experimentally observed as a spectral peak by electron energy-loss spectroscopy (EELS). Fig. 2 shows plasmon-loss spectra of Al, Si and diamond acquired by EELS. Their peak values show good agreements with those on Table 1. In the spectra of Al and Si, weak peaks are observed at the positions of integer multiples of their plasmon energies (highest peaks). These weak peaks are the energy-loss spectra caused by successive plasmon excitations (twice, three times and more). The plasmon peaks of Si and diamond are broader than that of Al. This is due to a large attenuation of plasma oscillations of Si and diamond, in other words due to the collapse of the plasma oscillations caused by interband transitions of the valence electrons.
    (By Associate Professor Yohei Sato, Tohoku University)

    Fig. 2. Plasmon peaks of Al, Si and Diamond in EELS spectra

  • 帯電




    If a specimen has no conductivity, part of incident electrons accumulate on the specimen. This phenomenon is called "charging." Charging disturbs normal transmission and scattering of the incident electrons, thus abnormal contrast and distortion of the image occur. To prevent charging, conductive coating is performed.

  • 対物絞り

    objective aperture


    明視野像や暗視野像を得るために透過波や回折波のひとつを取り込むための絞り。対物レンズの後焦点面に挿入される。 絞りの直径は5~100μm。以前は格子像、構造像をとるときにも挿入されたが、最近は使わないことが多い。絞りを使って急なカットを入れたデータを使ってコンピュータ処理をするとアーティファクトが現れることがあるためである。

    The "objective aperture" is used for accepting a transmitted wave or one of diffracted waves to obtain a bright-field image or a dark-field image. The objective aperture is inserted into the back focal plane of the objective lens. The diameter of the objective aperture is 5 μm to 100 μm. It is noted that this aperture was inserted when obtaining a lattice image or a structure image, but recently, it has not been used. The reason for this is as follows. If computer processing is applied to the data which has a sharp cut due to the aperture, artifacts can appear in the processed image.

  • 対物レンズ(オブジェクティブレンズ)

    objective lens



    The "objective lens" is the first-stage lens to form an image using electrons exiting from the specimen. The objective lens is the most important lens in the imaging lens system because the performance of this lens determines the image quality (resolution, contrast, etc). A good objective lens has both a small spherical aberration (Cs) coefficient and a small chromatic aberration (Cc) coefficient. To decrease these coefficients, shortening the distance between the two magnetic poles and decreasing the bore diameter of the polepiece and are required. Since the side-entry-type specimen holder is inserted between the two magnetic poles, there is a limitation on shortening the distance. For the top-entry-type specimen holder, an asymmetric popiece whose upper bore diameter is larger than that of the lower one is used.

  • 滞留時間

    residence time



    "Residence time" is a time when a particular compound or element spends in a system, or a time when a reactant spends in a process vessel or contacts a catalyst.

  • 多結晶




    A crystal composed of crystalline particles with different crystal orientations.

  • 多重散乱

    multiple scattering



    When the incident electrons travel a specimen, these electrons strike the constituent atoms in the specimen many times until these electrons exit from the specimen and change their traveling direction. This (scattering) phenomenon is termed "multiple scattering." Among the theories related to multiple scattering, the dynamical diffraction theory, which treats multiple scattering due to elastic scattering (Bragg reflection), provides the intensities of the incident and diffracted waves as a function of specimen thickness and scattering angle.

  • 多段加速電極

    multi-stage acceleration electrode



    The "multi-stage acceleration electrode" consists of a cascade of acceleration electrodes used for accelerating an electron beam, which is emitted from the electron gun, up to a required voltage. In a 200 kV TEM, a six-stage acceleration electrode is adopted.

  • 立ち上がりエネルギー

    onset energy



    The onset energy means the energy at which a spectral intensity rises sharply in the EELS valence-loss spectrum or core-loss spectrum. This energy corresponds to the band gap in the valence-loss spectrum and to the bottom of the conduction band in the core-loss spectrum.

  • 多波近似

    many-beam approximation



    Many-beam approximation is an approximation method to interpret the diffraction intensity and TEM image, which takes account of not only a Bragg-reflected beam (diffracted wave) from one lattice plane, but also many reflected beams from other lattice planes.

  • 多目的用ポールピース

    multiuse polepiece



    The "multiuse polepiece" allows the specimen holder to be tilted to more than ±35°. This polepiece makes it possible to attain a Cs of 1.0 mm, a Cc of 1.4 mm and a spatial resolution for TEM image of 0.23 nm at an accelerating voltage of 200 kV. For analytical case, the objective aperture is inserted below the lower pole of the polepiece to avoid unnecessary X-rays from the aperture. This aperture setting causes a problem that the diffraction pattern is not formed on the aperture plane, which leads to a difficulty in acquiring the dark field image from one diffraction spot and the bright field image without the influence of surrounding diffraction spots. It is noted that there is option to insert a special aperture at the polepiece gap to obtain correct bright- and dark-field images.

  • 単位胞

    unit cell



    The minimum unit of the periodicity of a crystal. The size and form of the unit cell is defined by six lattice parameters or constants (a, b, c, α, β, γ).

  • 短距離秩序度

    short-range order parameter



    In the case of a binary alloy, "short-range order parameter" means a probability of existence of atom B around atom A. It can be measured from the intensity of diffuse scattering that appears around a reflection specific to the ordered phase.

  • 単結晶

    single crystal



    The single crystal is a crystal in which the constituent unit cells are aligned in the same orientation. A large single crystal is obtained under a specific growth condition.

  • 単粒子解析

    single particle analysis


    試料作製法や解析ソフトウエアの発展、ならびにCMOSを用いた直接露光検出器の登場により、単粒子解析法の高分解能化・実用化が進んだ。極めて少量(密度: 数mg/mL、容量: 数µL/グリッド)のサンプルでの解析が可能で、結晶化の困難なタンパク質の構造解析にも有効である。2018年現在、最高到達分解能は0.16 nmである。


    ほぼ単一の構造の高純度のタンパク質粒子を水溶液に分散させる。タンパク質の構造を損なわないようにするために急速凍結(-180°C以下)により氷包埋する。タンパク質は C、H、O、N、S など軽元素で構成され電子顕微鏡像のコントラストが低いため、試料作製の際、タンパク質粒子を取り囲む氷の厚みを十分薄くすることが重要である。






    電子顕微鏡を用いた構造解析法には、電子線結晶構造解析法、電子線トモグラフィー、単粒子解析法がある。電子線結晶構造解析法では、二次元結晶あるいは薄い三次元結晶を用いて、X線構造解析と類似の方法で構造解析する。分解能は0.2 nmを切っている。電子線トモグラフィーでは、一つの試料を電子顕微鏡内の試料ホルダーで連続的に傾斜して、さまざまな角度からの投影像を撮影し、得られた画像を逆投影して三次元構造を得る。この方法では、加算平均による画像のS/N比の向上を実施することはできない。生体物質への応用では、細胞レベルでの機能構造の解析に用いられており、分解能は数〜10 nmオーダーである。しかし、得られたトモグラムに同じタンパク質粒子が数多く含まれる場合はサブトモグラム平均が可能で、この方法による分解能向上は0.3 nmに近い領域に到達している。
    従来から用いられているタンパク質の構造解析法は、X線結晶構造解析法ならびに核磁気共鳴法(NMR)である。前者ではサイズが10 µm以上の結晶が必要であり、結晶化できないタンパク質は構造解析できない。NMRでは解析できる分子量が~5万以下という制限がある。単粒子解析法にはこれらの制限はなく(ただし、分子量10万以下の小さな分子では画像のS/N比が悪く現時点での課題)、分解能はX線結晶構造解析と同程度に近づいており、単粒子解析法の発展と利用が期待されている。

    (大阪大学 難波啓一特任教授、加藤貴之特任准教授 校閲)
    single particle analysis ⇒
    (データ提供: 大阪大学 難波啓一特任教授、加藤貴之特任准教授)

    An electron microscopy method to obtain the three-dimensional (3D) structure of biological macromolecules, such as proteins and nucleic acids, by analyzing electron microscope images of the macromolecules (proteins, etc.) recorded as dispersed particles (single particles). A solution containing a protein is made into a thin film on a holey carbon film attached on an EM grid and is then rapidly frozen so that the particles are embedded in an amorphous ice film. TEM images are taken at Liq.N2 temperature, and the 3D structure is reconstructed by image processing and analysis.
    A number of projection images of the 3D structures of protein particles in various orientations are recorded in the acquired Cryo-TEM images. Each particle image is rotated and translated in the image plane to collect the images having the same external shape and the same density distribution to sort them into groups of different 3D orientations. Then, the images in the same groups are added and averaged to improve the signal-to-noise ratio of the images. Next, the Euler angles of the projection orientations (angles of the particles against the image plane in the present case) are estimated. Finally, the 3D structure of the protein is reconstructed by back projection of these particle images along the estimated Euler angles.
    Single particle analysis has been dramatically improved in its achievable resolution and practical application by the advent of a CMOS direct electron detector, together with innovations in specimen preparation techniques and analysis software programs. The method is applicable to an extremely small amount of sample solution (protein concentration: several mg/mL, solution volume: several µL/grid), and is especially effective for structural analysis of proteins that are difficult to crystallize. As of 2018, the highest resolution achieved with the method is 0.16 nm.

    Specimen preparation and observation method

    A highly purified protein solution is prepared in which protein particles with a homogeneous structure are dispersed. The protein particles are ice-embedded by rapid freezing (at –180 °C or less) so as to preserve their structures. It is important that the ice film embedding the protein particles must be prepared as thin as possible to produce high contrast TEM images because proteins are composed of light elements (C, H, O, N, S, etc.) and produce low contrast against the ice film by a small difference between their densities.
    The specimen grid is inserted into the microscope column with its frozen state kept. TEM images of the specimen are recorded at Liq.N2 temperature. To suppress the damage to the specimen due to electron-beam irradiation, the electron dose onto the specimen must be set low. The specimen is observed using phase contrast because protein particles consisting of light elements are difficult to observe using scattering contrast. For observation of protein particles, a large amount of defocus of the objective lens (–0.5 to several µm) is used to enhance the image contrast, particularly in a low spatial frequency range to allow the detection and orientation determination of the particles.

    Image acquisition

    Images of protein particles recorded at a low electron dose have a very low-signal-to-noise ratio (S/N). To obtain the particle images with a high S/N, hundreds to thousands of Cryo-TEM images are collected, from which several tens of thousands to several hundreds of thousands of particle images are extracted and added and averaged after image classification and alignment. In recent years, several thousands of Cryo-TEM images are automatically acquired over several days using an automatic image acquisition system.
    It is emphasized that the electron-beam-induced drift of ice-embedded protein particles is the main cause of degrading the resolution of the TEM image in the single particle analysis method. Extremely high frame rate of direct electron detectors (scintillator not used) that allow single electron counting and movie-mode image recording has improved the resolution of the TEM image. Recording a TEM image in the movie mode at a frame rate of 5 to 10 frames/sec allows the particle image drift to be greatly reduced by post image processing, namely motion correction of the particle images between the frames enables acquisition of high-resolution protein particle images.

    Image analysis

    From several thousands of the Cryo-TEM images, several tens of thousands to several hundreds of thousands of the protein particle images are automatically extracted using a particle detection software program. Since the particle images are projected in various orientations, the extracted images are rotated and translated so as to sort them out into many classes of the projection images in the same orientations. Then, the images sorted in each class are aligned in their positions and orientations and are averaged. As a result, 100 to 200 protein particle images with a high S/N are obtained. In this step, the 3D orientations of the particle images (Euler angles or the angles of the particles against the image plane in the present case) are not yet determined.
    To obtain the Euler angles, first an initial particle model with arbitrary orientations is given. Secondary, the projection images of the model are produced. The Euler angle of each particle image is estimated by a comparison of the projection images and the TEM image. The particle TEM images with the estimated Euler angles are subjected to back projection to produce an initial 3D structure of the particle. Then, this 3D structure is subjected to projection again to create the projection images. The re-projected images and the particle TEM images are compared to estimate the Euler angles again. These particle images are back-projected to obtain a better 3D structure in the next step. These steps are repeated until the obtained 3D structure is converged. In each step of calculations, the results are evaluated by statistical approaches. Finally, the most probable 3D structure is obtained.

    Comparison with other analytical methods

    Structural analysis methods using electron microscopy include Electron Crystallography, Electron Tomography and Single Particle Analysis. In Electron Crystallography, a 2D or thin 3D crystal is prepared and analyzed using techniques similar to those of X-ray Crystallography. Electron Crystallography provides a resolution better than 0.2 nm. In Electron Tomography, one specimen is placed in the specimen holder in the microscope column, and is subjected to serial tilt-series imaging at various angles. Then, back projection is applied to the acquired projection images for obtaining the 3D structure. In the method, it is not possible to improve the signal-to-noise ratio and the resolution of the images by averaging. For biological applications, the method is used for analysis of functional structures at the cell level, its resolution being on the order of several nm to 10 nm. But when the tomogram contains many particles of the same proteins, the use of the sub-tomogram averaging method improves the resolution close to 0.3 nm.
    Conventionally-used structural analysis methods of proteins are X-ray Crystallography and Nuclear Magnetic Resonance (NMR) spectroscopy. The former method requires a crystal with a size of 10 µm or more. Thus, the method cannot be applied to proteins that are unable to crystallize. The latter method can be used only for proteins with a molecular weight of ~50,000 or less. However, Single Particle Analysis does not have such restrictions and its resolution has been becoming as high as that of X-ray Crystallography, although at present it is still difficult to apply this method to proteins with molecular weight less than 100,000 because of low S/N of their TEM images. In the future, the advancement and the more use of Single Particle Analysis are highly expected.

    (Proofread by Specially Appointed Professor Keichi Namba and Specially Appointed Associate Professor Takayuki Kato, Osaka University)

    single particle analysis
    Data courtesy: Specially Appointed Professor Keichi Namba and Specially Appointed Associate Professor Takayuki Kato, Osaka University

  • ターボ分子ポンプ

    turbo-molecular pump



    A mechanical, dry vacuum pump that does not use oil. In the turbo-molecular pump, a high-speed rotor provides momenta to residual gas molecules in the pumping direction and the gas molecules are pumped. A rotary pump or the other pump is required to evacuate the backside of the turbo-molecular pump. The pump operates at low to high vacuum. The working pressure is 10-1 to 10-8 Pa. Recently, problems of sound noises and mechanical vibrations have been solved. Any gas can be pumped by this pump. Unlike the diffusion pump, the pump is suitable for pumping water H2O. Thus, the pump is sometimes used for a biological TEM. The price of the pump is higher than the ion pump. Care has to be paid for mechanical failure.

  • 第一原理計算

    first principle calculation



    "First principle calculation" is a method to calculate physical properties directly from basic physical quantities such as the mass and charge, Coulomb force of an electron, etc. based on the principle of quantum mechanics. In other words, the calculation derives physical properties directly from the basic principle without introducing adjusting parameters or modeling which are used to find agreement between theoretical calculations and experimental results. Starting from the Coulomb interaction between electrons, atomic nuclei and electron-atomic nucleus, the properties of materials (mainly electronic properties) are non-empirically calculated. Along with the great improvement of the computer performance, the calculations for systems containing many atoms have become possible with lower cost and high speed, thus the method is increasingly prevailing. The method is indispensable for predicting properties of new materials and of understanding properties of existing materials. In the TEM field, the method is used for the study of fine structures of EELS spectra that reflect the density of states of materials.

  • 大角度収束電子回折法

    LACBED large-angle convergent-beam electron diffraction



    LACBED (a)(b)⇒

    (b) 収束半角をブラッグ角以上にした場合

    LACBED (c)(d)⇒
    (c) 通常の収束電子回折法で収束角をブラッグ角より大きくした場合の光線図。

    (d) 大角度収束電子回折法での光線図。

    加速電圧:200kV, 試料:Si [111]

    In conventional CBED, if the angular diameter of a diffraction disk exceeds the Bragg angle, the disk overlaps with an adjacent diffraction disk. Thus, the angular diameter is limited to an angle smaller than the Bragg angle. The use of the large-angle convergent-beam electron diffraction (LACBED) technique breaks through the angular limitation. Using a condenser-objective (CO) lens, when a specimen is placed on the focus position of the CO lens, the bright-field and dark-field images are formed on the image plane (on the selected-area aperture) but these images overlap with each other. When the specimen is shifted upper or lower from the focused position of the incident beam, the bright-field and dark-field images on the selected-area aperture are separated. If only the bright-field image is chosen with the selected-area aperture and the intermediate lens is set to take a diffraction pattern (the diffraction mode), the bright-field diffraction disk covers an angle of three to four times larger than that for the conventional CBED disk. Since the LACBED pattern contains information on both the image and diffraction pattern, it is effectively utilized for identification of lattice defects and analysis of strains at interfaces.

    (a) In the case of convergence semi-angle to be equal to the Bragg angle or smaller.
    In conventional CBED, the convergence semi-angle a is limited at the maximum to the Bragg angle θ to avoid the overlap of adjacent diffraction disks.

    (b) In the case of the convergence semi-angle to be larger than the Bragg angle.
    When the convergence semi-angle a exceeds the Bragg angle θ, the adjacent diffraction disks overlap, thus making it impossible to extract information on each diffraction disk.

    (c) Ray diagram of conventional CBED where the convergence semi-angle is set to an angle larger than the Bragg angle.
    In conventional CBED, the incident beam is focused on a specimen and the objective lens is focused on the specimen. A diffraction pattern is formed on the back focal plane of the objective lens and an image of the specimen (a spot image in this case) is formed on the selected-area aperture. When the convergence semi-angle of the incident electron beam is set to an angle larger than the Bragg angle, a transmitted wave disk and diffracted wave disks overlap with each other on the back focal plane of the objective lens. The image formed by the transmitted wave and images formed by diffracted waves are superposed on the selected-area aperture to form a spot image.

    (d) Ray diagram of LACBED.
    ①In LACBED, the specimen position is shifted to a higher (lower) position from the focused position of the incident beam without changing the excitation of the objective lens.
    ②The diffraction pattern is formed on the back focal plane of the objective lens as it is in (c). The image of the specimen, which is formed on the selected-area aperture in (c), is shifted to an upper (lower) position, and on the selected-area aperture the (spot) image of the transmitted wave and (spot) images of the diffracted waves are separated.
    ③If only the transmitted spot (beam) is selected using the selected-area aperture in the image observation mode of the intermediate lens system, and then the intermediate lens system is switched to the diffraction mode, a large-angle convergent-beam electron diffraction (LACBED) pattern formed only by the transmitted wave is obtained. The LACBED pattern removes the overlap due to the diffracted wave disks and extends its angular diameter beyond the limitation of the diffraction (Bragg) angle.

    LACBED pattern of Si [111] taken at an accelerating voltage of 200 kV.

  • ダイナミックTEM

    DTEM Dynamic TEM


    通常の透過電子顕微鏡においては30分の1秒(テレビレート)の時間分解能でしか画像記録できないが、光源や記録系を高速なものに置き換えてナノ秒~フェムト秒オーダーの間隔で透過電子顕微鏡像を取得する技術をDynamic TEM (DTEM)と呼ぶ。パルスレーザによる光電子放出を用いた電子銃が光源として用いられる。電子源からのパルスに試料に照射するパルスレーザを同期させて、高い時間分解能での化学反応過程や結晶化の過程を観察することができる。

    In an ordinary TEM, the time resolution of image recording is limited to 1/30 seconds (TV rate). However, the Dynamic TEM (DTEM) achieves a much higher time resolution of the order of nano seconds to femto seconds by the combined use of an electron source generating electron pulses and a fast recording system. A DTEM is equipped with a laser-pulse-driven photoelectron source and a pulse-laser specimen-irradiation system. By synchronizing the electron beam pulse with the pulse laser for the specimen, one can observe chemical reaction processes and crystallization processes with such a high time resolution.

  • ダイナミックレンジ

    dynamic range



    A quantity that expresses a reproducibility capability of the signal intensity. The "dynamic range" is defined as the intensity range obtained by subtracting the noise level from the maximum signal level. The dynamic range of the digital signal is expressed by the number of bits.

  • ダイヤモンドナイフ

    diamond knife



    A diamond knife is used to prepare an ultrathin section in ultramicrotomy. The diamond knife was originally developed to cut hard inorganic materials, which cannot be cut with a glass knife. Today, the diamond knife is used also for resin specimens because the glass knife is damaged even by a resin specimen, that is, the blade edge of the knife is likely to become dull. Thus, the diamond knife currently plays an essential role in preparing a uniform ultrathin section.

  • 脱出深さ(電子などの)

    escape depth



    The "escape depth" is the depth of a specimen from which secondary electrons, characteristic X-rays, or Auger electrons can escape.

  • 脱ガス




    "Degas" is to emit gasses from an object by artificial operation. In the case of a TEM, degas is carried out by evacuation of the electron-gun and the column and by heating these parts to accelerate gas emission. On the other hand, natural gas desorption is termed "outgas."

  • 弾性散乱電子

    elastically scattered electron



    Elastically scattered electrons are defined as the electrons which are scattered (change in their traveling direction) by constituent atoms in a specimen without losing their energy. When a specimen is a crystal, elastically scattered electrons become diffracted waves that travel in specific directions given by the Bragg condition. As a specimen is thinner, the intensity of a TEM image or a diffraction pattern is explained by elastically scattered electrons. As a specimen is thicker (~10 nm or thicker), the effect of inelastically scattered electrons must be taken into account.

  • チェレンコフ放射

    Cherenkov radiation



    When the velocity of a charged particle exceeds the velocity of light in a substance, light is emitted from the substance. This light is called the Cherenkov radiation. The intensity of the radiation is inversely proportional to the square of the wavelength of the radiation. The Cherenkov radiation is also observed when an electron beam illuminates a specimen in a TEM, which provides information on the refractive index of the specimen.

  • 置換




    "Substitution" means that an atom or a group of atoms in a crystal or a molecule is substituted with other atom or other group of atoms.

  • 置換原子

    substitutional atom



    When the other kind of atom (solute atom) occupies an atom position instead of an original atom, the solute atom is termed a "substitutional atom."

  • 中間レンズ

    intermediate lens


    対物レンズと投影レンズの間にあるレンズ。励磁電流を調整して中間レンズの焦点距離を変えて、対物レンズによって作られる回折図形またはTEM像に焦点を合わせて、それらを拡大し投影レンズの物面にそれらの像を作る。通常、中間レンズは3段構成で、1段目は主に焦点合わせに、2段目は像の拡大に、3段目は主に無回転像を作るために使われる。中間レンズの倍率は~0.5~100倍。倍率100倍のときの内訳は1段目 4~5倍、2段目 ~10倍、3段目 2~3倍。

    The "intermediate lens" is placed between the objective lens and the projector lens. The intermediate lens works in the following way. The intermediate lens changes focusing position either on a diffraction pattern or a TEM image produced by the objective lens by adjusting its excitation, and forms the magnified pattern or image on the object plane of the projector lens. Normally, the intermediate lens consists of three parts: The first part mainly selects focusing position, the second part magnifies the focused pattern or image, and the third part mainly achieves rotation-free condition. The magnification of the intermediate lens is varied from ~0.5× to ~100×. When the total magnification is 100×, the magnifications for the first, second and third parts are 4× to 5×, ~10×, and 2× to 3×, respectively.

  • 中心対称




    "Centro-symmetry" means that a crystal is symmetric with respect to a certain point.

  • 超音波洗浄

    ultrasonic cleaning



    "Ultrasonic cleaning" is a technique to remove contaminants on a specimen and parts of a TEM. In "ultrasonic cleaning," a cleaning solution is vibrated by an ultrasonic transducer and hits the object to clean. Since the cleaning solution can enter the fine gaps of the object, ultrasonic cleaning is suitable for precision components. Acetone is used as a cleaning solution in many cases.

  • 超音波ナイフ

    ultrasonic knife



    An ultrasonic knife is a diamond knife that thins a specimen while vibrating the blade head of the knife using ultrasonic wave. In ordinary thinning with a diamond knife, a pressure can be applied to the cutting direction of the specimen. This may cause “compression” (deformation of the specimen due to compression in the up-and-down direction) or falling of granules with different hardnesses such as lipid droplets. The ultrasonic knife which vibrates its blade head right-and-left in cutting, makes it possible to disperse the pressure to the specimen. Owing to this feature, the ultrasonic knife prevents “compression” or the falling of the granules.

  • 長距離秩序度

    long-range order parameter



    In the case of binary alloys, a degree of order of atom species A and B increases with decreasing temperature after a substance undergoes a transition from a disordered phase to an ordered phase. The "long-range order parameter" means this degree of order. It can be measured from the intensity change of a specific reflection that appears in an ordered phase.

  • 超高圧電子顕微鏡

    UHV-EM ultra-high voltage electron microscope



    UHV-EM : ultra-high voltage electron microscope ⇒

    "Ultra-high voltage electron microscope (UHV-EM)" is an electron microscope which accelerates electrons with a high voltage of 1000 kV or higher. The wavelength of an electron at 1000 kV is shortened down to 0.00087 nm. Utilizing the short wavelength, a resolution of about 0.1 nm has been obtained, and light elements such as carbons have been clearly observed. However, recent high resolution imaging has been achieved by 300 kV microscopes equipped with a spherical aberration corrector. The advantage of UHV-EM is the capability of observing thick specimens using its high transmission power, of investigating radiation damage of specimens using the high energy electron beam and of investigating chemical reaction at controlled conditions utilizing an enough space of a specimen chamber.

    The ultra-high voltage electron microscope (UHV-EM) is an electron microscope which accelerates incident electrons with a high voltage of 1000 kV or higher. The wavelength of an electron at 1000 kV is shortened down to 0.00087 nm. Utilizing the short wavelength, a spatial resolution of the microscope image with about 0.1 nm has been attained. The other advantages of UHV-EM include observation of thick specimens using its high transmission power, investigation of radiation damage of specimens using its high-energy electron beam, and study of chemical reactions under controlled environments by utilizing a large space of the specimen chamber.

  • 超格子




    "Superlattice" is formed, for example, when a structural modulation occurs on a crystal structure to have a longer period (normally an integral multiple of the original period) than that of the original crystal structure. Such a modulation can be formed in a low-temperature phase due to phase transformation. An artificial superlattice is produced as a long-period multi-layer structure which is composed of more than two kinds of layer crystals deposited by molecular beam epitaxy (MBE). The superlattice structures are used for quantum-well laser diodes, high-temperature superconductive materials, and magnetic materials.

  • 超高真空

    ultra-high vacuum



    A high vacuum of 10-5 Pa or better. To achieve an "ultra-high vacuum," high-end technology is required, which includes selection of appropriate materials of pumps, containers, etc.

  • 超高分解能用ポールピース

    ultra-high-resolution polepiece



    The "ultra-high-resolution polepiece" makes it possible to obtain a Cs of 0.5 mm, a Cc of 1.0 mm and a spatial resolution for a TEM image of 0.19 nm at an accelerating voltage of 200 kV, in which the tilt angle of a specimen holder is limited to ±(20°to 25°). It is used for high spatial resolution microscopy and for analytical microscopy from nm diameter areas. This polepiece gives rise to a drawback which cannot be overlooked. That is, the correct bright and dark field images cannot be often obtained. The reason is as follows: The objective aperture is normally inserted into the lower part of the polepiece to prevent the objective aperture from contacting the specimen holder when it is tilted. In this case, the diffraction pattern is formed above the aperture plane. As a result, the aperture cannot often select one diffraction spot but takes influence of neighbor spots. Thus, the bright and dark field images are influenced by the effect of other diffraction. It is noted that there is option to insert a special aperture at the polepiece gap to obtain correct bright- and dark-field images.

  • 長周期構造

    long period structure



    For example, in the phase of CuAuⅠ, five ordered lattices are aligned in a direction followed by another five ordered lattices with an anti-phase shift to the former lattices, resulting into formation of a structure with a unit of 10 times larger than the original lattice. Such a structure is called a "long period structure." The phase CuAuⅠ appears in a narrow temperature range between the ordered phase and the disordered phase. In a diffraction pattern, the reflections from the ordered phase split to diffraction spots appearing at the positions corresponding to a period of 10 times that of the ordered phase. Long period structures appear in intermetallic compounds and SiC.

  • 超薄切片

    ultrathin section


    電子線が透過できるほどに薄くスライスした切片。多くの場合、厚さが100 nm以下の切片のことを指す。

    An ultrathin section means a section sliced thin enough to transmit an electron beam. In many cases, the ultrathin section has a thickness of 100 nm or less.

  • 直接露光検出器

    direct electron detector



    The direct electron detector is a detector in which accelerated electrons are directly received by an image sensor of CCD or CMOS instead of using a scintillator. Those electrons are converted directly into electric signals, whereas in a usual case, the accelerated electrons are received by a scintillator, converted to light and then the light is transferred to a CCD or CMOS using a lens system or an optical fiber system. Very large electric signals are produced in the case of the direct detector because the scintillator converting electron signals to light signals is not used and the incident electrons possess a very high energy than the light signals produced in the scintillator. The direct electron detector has 10 to 100 times higher sensitivity for electron detection than the scintillator - CCD system. Taking advantage of this high sensitivity, the direct electron detector is effectively used for cryo-electron microscopy (observation of biological materials with cooling), which requires a very low electron dose to avoid specimen damage. In addition, nonuse of the scintillator enables the spatial resolution of a TEM image to be improved. Furthermore, the advantage of its high read-out rate is utilized as a detector taking scanning images.
    However, damage to the detector due to electron-beam irradiation is unavoidable. Thus, replacement of the sensor is necessary if the total electron dose reaches approximately 109.

  • ツーウィンドウ法

    two-window method


    EELSによる定性的元素マッピングに用いる方法。試料の同じ場所から、ある元素の内殻励起の直前のバックグラウンド強度I1と励起の直後のスペクトル強度I2を測定しI = I2/I1を計算する方法。この方法で二次元マッピングすると、定量性には欠けるが簡単に定性元素マッピングができる。

    A method used for qualitative element (elemental) mapping by EELS. In the "two-window method," a background intensity immediately before the inner-shell excitation (I1) and the peak intensity at the inner-shell excitation (I2) of a certain element are acquired. The ratio I = I2/ I1 is calculated. This method enables us to easily perform qualitative element mapping though it does not have a sufficient quantitative accuracy.

  • 低エネルギー電子顕微鏡

    LEEM low energy electron microscope


    入射電子線のエネルギーを電場で数ボルトから数百ボルトに低減して試料に照射し、試料から後方弾性散乱された電子を試料直上の電場で加速し、結像レンズによって拡大像をスクリーンもしくは撮像カメラによって観察する装置。空間分解能は5~10nm程度。結像レンズ系で回折パターンを形成し、絞りでLEED (low energy electron diffraction) の回折スポットを選択して暗視野像を得ることもできる。表面構造の研究に使われ、試料周りは超高真空に保たれる。また、結像系が同一なPEEM (photo emission electron microscope)の機能が付加されていることが多い。

    A "LEEM (low energy electron microscope)" is an instrument to obtain a surface image of a specimen. The incident electron energy is reduced to several V to several 10 V, and elastically-backscattered electrons from a specimen are accelerated by an electric field just above the specimen. The formed image is enlarged by the imaging lens and observed through a screen or a camera. The spatial resolution of LEEM is 5 to 10 nm. A dark-field image can be obtained by selecting a diffraction spot of LEED (low energy electron diffraction) with an aperture. The specimen area is kept at an ultrahigh vacuum to obtain surface structural information. LEEM is often accompanied with a function of PEEM (photo emission electron microscope) which has the same imaging system as that of LEEM.

  • 低角度散乱暗視野法

    LAADF-STEM low-angle annular dark-field scanning transmission electron microscopy



    半導体素子(CPUのn-チャンネルMOSFET)の断面薄膜試料のSTEM像 ⇒
    加速電圧: 200 kV、入射電子線の収束角: 半角11 mrad
    図(a) HAADF-STEM像。青矢印で示したように、TaやWなど重い元素の存在する部分が明るく観察されている。検出器の取り込み角:半角46 - 208 mrad
    図(b) LAADF-STEM像。赤括弧で示した領域中のSiNx層は、青括弧で示したSiO2の領域と比較して、明るく観察されている。この層構造はHAADF像においてほとんど観察することができない。また、赤矢印で示したように格子欠陥も観察されている。検出器の取り込み角:半角14 - 63 mrad

    図(a) HAADF-STEMにおける入射電子線の収束角と散乱電子線の検出器への取り込み角の関係。検出器の典型的な取り込み角はβ1 ~ 50 mrad,β2 ~200 mradである。高角度に散乱された非弾性散乱電子を検出する。200 kVの収差補正電子顕微鏡の場合、αは25 mrad程度である。通常、ABF検出器やLAADF検出器はHAADF検出器の下部に配置される。
    図(c) LAADF-STEMにおける入射電子線の収束角と散乱電子線の検出器への取り込み角の関係。入射電子線の収束半角をαとすると検出器の取り込み角は、β1はα より少し大きな角度、β2は 60 mrad程度に設定する。回折波と中低角度に散乱された非弾性散乱波を検出する。

    Low-angle annular dark-field scanning transmission electron microscopy (LAADF-STEM) is a STEM method which receives diffracted or inelastically scattered electrons at low to medium angles (25 to 60 mrad) using an annular dark-field (ADF) detector. A STEM image is acquired by displaying the integrated intensities of the electrons in synchronism with the incident probe position. It is noted that the LAADF image shows diffraction contrast or difference of specimen thickness dependence.
    LAADF-STEM is used in place of HAADF-STEM for a specimen composed only of light elements (molecular crystals, two-dimensional crystals, organic materials like macromolecules, biological materials, etc.). This is because the HAADF image does not have a high signal-to-noise ratio due to weak elastic and inelastic scattering at high angles for such light-element specimens. LAADF-STEM enables us to obtain a high-resolution image with a high signal-to-noise ratio whose intensity depends on the atomic number.

    STEM images of the cross-sectional thin film of a semiconductor device (an n-channel MOSFET of CPU). (Accelerating voltage: 200 kV, Convergence semi-angle of the incident electron beam: 11 mrad)

    Fig.(a) HAADF-STEM image taken at an acceptance semi-angle of the detector of 46 to 208 mrad. As is shown by a blue arrow, only a region where heavy atoms (Ta, W, etc.) exist are observed with bright contrast.
    Fig.(b) LAADF-STEM image taken at an acceptance semi-angle of the detector of 14 to 63 mrad.
    SiNx layers in the regions indicated by a red parenthesis are observed brighter than SiO2 regions indicated by a blue parenthesis. Such layer structures are hardly seen in the HAADF image. In addition, the LAADF image also visualizes lattice defects indicated by red allows. 

    Comparison of Ray diagrams of two detectors

    Fig.(a) Relationship between the convergence semi-angle of the incident electron beam and acceptance semi-angles of the detector for HAADF-STEM. Typical inner and outer semi-angles of the detector are respectively β1 = ~50 mrad and β2 = ~200 mrad, detecting inelastically scattered electrons at high angles. The value of the convergence semi-angle α is approximately 25 mrad for a 200 kV Cs-corrected TEM. Usually, an ABF detector and a LAADF detector are placed below a HAADF detector.

    Fig.(c) Relationship between the convergence semi-angle of the incident electron beam and acceptance semi-angles of the detector for LAADF-STEM. The inner and outer acceptance semi-angles of the detector are respectively taken as that β1 is a little larger than α and β2 is ~60 mrad, where α is the convergence semi-angle. It should be noted that the diffracted waves and inelastically scattered electrons over low to medium angles are used for LAADF-STEM.

  • 定在波

    standing wave



    "Standing wave" means that the ratio between the amplitude of a wave at a certain point and that at the other point is constant regardless of time. When an electron wave exactly satisfies a Bragg reflection in a crystal, the incident wave and the diffracted wave form a standing wave.

  • 定量組成分析

    quantitative compositional analysis



    "Quantitative compositional analysis" is to analyze not only the composition (kinds of constituent elements) but also the element abundance ratio (concentrations) of a substance. The composition is analyzed from the energy-peak positions in a spectrum and the element abundance ratio is quantitatively analyzed from the peak intensities.

  • 転位



    図1(a)は立方晶内に存在する刃状転位近傍の原子の並びを示す模式図である。一枚余分な格子面である余剰半面(extra half plane)が結晶に導入されており(黒線で図示)、この面の終端が刃状転位線である。転位線の周りで格子に沿って一回りする(バーガース回路:オレンジの矢印で図示)と元の格子点に戻らず、一格子分だけずれたところにくる。このずれをバーガースベクトル(赤矢印で図示)といい、転位により導入された原子位置のずれの方向と量を特徴づける量である。刃状転位におけるバーガースベクトルは転位線に垂直である。図1(b)は立方晶内に存在する螺旋転位近傍の原子の並びを示す模式図である。転位線は "ずれ" の始まる位置にあって、図の上から下に走っている。螺旋転位では、転位線の周りで格子に沿って一回りするバーガース回路は螺旋状になり、バーガースベクトル(赤矢印)と転位線は平行である。

    図1 (a)刃状転位の模式図 (b)螺旋転位の模式図 ⇒図1

    図2 シリコン単結晶での転位の明視野像。加速電圧: 200 kV。 ⇒図2

    図3 (a)SrTiO3の小傾角粒界に並んだ粒界転位を[001]方向から観察した原子分解能暗視野STEM像。(試料:東京大学幾原研究室提供) ⇒図3

    "Dislocation" is a linear or one dimensional defect in a crystal. When a part in a crystal is displaced against the other part, the line at which the displacement is starting is called a dislocation or a dislocation line. There are two types of dislocations, or edge dislocations and screw dislocations. The crystal around the dislocation is highly strained. Plasticity of a crystal is explained by motion and multiplication of dislocations.
    Fig. 1(a) schematically shows the atomic arrangement near an edge dislocation of a cubic crystal. An extra lattice plane (called an extra half plane) is shown by a black line. The end line of the extra half plane is the edge dislocation or edge dislocation line. Suppose a circuit along the crystal lattice around the dislocation line (Burgers circuit: indicated by yellow lines with allows), the end of the circuit after one round does not come back to the original lattice point but comes to the next lattice point. This displacement is termed the Burgers vector (indicated by a red allow), which characterizes the direction and amount of the atomic displacement caused by the dislocation. The Burgers vector (shown by a red line) of the edge dislocation is perpendicular to the dislocation line.
    Fig. 1(b) schematically shows the atomic arrangement near a screw dislocation. The screw dislocation (line) exists at the start (or end) line of the displacement and runs from the top to the bottom of the figure. The Burgers circuit in this case is seen to be spiral. The Burgers vector of the screw dislocation is parallel to the dislocation line (indicated by a red allow).
    Fig. 2 shows a bright-field image of dislocations in a silicon crystal. The dislocations (lines) are seen to be dark (black) lines because the regions near the dislocations come into a Bragg reflection. Fig. 3 shows a [001] atomic-resolution dark-field STEM image of a small-angle grain boundary of SrTiO3. Edge dislocations are seen to be arranged along the grain boundary, creating a small orientation change between both sides of the crystal.

    Fig. 1.(a) Schematic of edge dislocation. (b) Schematic of screw dislocation.

    Fig. 2. Bright-field image of dislocations in a silicon crystal taken at an accelerating voltage of 200 kV.
    (a) A black line (indicated by arrow "a") shows a dislocation line running parallel to the specimen surface.
    (b) A black zigzag line (indicated by arrow "b") exhibits a dislocation running oblique to the specimen surface. The zigzag contrast is created by a dynamical diffraction effect.

    Fig. 3
    (a) [001] atomic-resolution dark-field STEM image of dislocations on a small-angle grain boundary of SrTiO3 taken at an accelerating voltage of 200 kV. (Specimen courtesy: Prof. Y. Ikuhara, The University of Tokyo)
    (b) Edge dislocations are clearly visualized by selectively displaying crystalline planes along the grain boundary.
    (c) Schematic of the edge dislocation (gray circles indicate atomic columns).

  • 転位ループ

    dislocation loop



    When oversaturated point defects (vacancies or interstitials) accumulate in a plate form, a closed dislocation is produced at the edge of the plate. The closed dislocation is called "dislocation loop." In the case of the vacancy plate, when the atomic planes neighboring to the vacancy plate collapse to retrieve the inherent atomic distance, a stacking fault is produced. Whether the dislocation loop is the vacancy type or the interstitial type is determined by examining whether the dislocation image is formed inside or outside of the dislocation for the diffraction conditions of the positive and negative deviations from the Bragg condition.

  • 点群(結晶点群)

    crystallographic point group



    In crystal symmetry, all the combinations of symmetries that exist with respect to a fixed point in a crystal are called "crystallographic point groups." Symmetry elements consist of rotation(1-, 2-, 3-, 4- and 6-fold), rotary inversion(4-), mirror(m) and inversion(i). 32 independent point groups are constructed by the combinations of the 8 symmetry elements.

  • 点欠陥

    point defect



    "Point defect" is defined as atomic-size defect. In particular, when no atom exists at a lattice point, this defect is called "vacancy type point defect." On the other hand, when an atom is introduced into a position other than a lattice point, the defect is termed "interstitial type point defect." Vacancies can exist in a crystal at the thermal equilibrium state and play an important role for diffusion of atoms. Interstitial atoms are normally impurity atoms, but they can be the same atoms of the crystal when the atoms at the lattice points are ejected by irradiating the crystal with high-energy particles. In the latter case, since the interstitial atoms are easy to move, the atoms are likely to disappear by recombination with vacancies.

  • 点分解能

    point resolution



    The minimum distance between two points at which these points appear to be separated. The "point resolution" of a TEM image becomes higher as the accelerating voltage is increased and the spherical aberration of the objective lens is decreased.

  • 点分析

    point analysis



    In spectroscopic analysis, "point analysis" is to acquire a spectrum from a point on a specimen by stopping an electron beam at the point.

  • ディフューズストリーク

    diffuse streak



    "Diffuse streak" means the streak intensity appearing in a (selected-area) diffraction pattern. The streak is produced from planar lattice defects (stacking faults, etc.) or linear lattice defects (atomic columns of different species or vacancy columns). Disorder of crystal structures can be deduced from the analysis of the diffuse streak.

  • ディフラクティブイメージング

    Diffractive imaging


    試料の回折図形からその像を再構成する手法。回折図形では収差の影響が少ないため、原理的には、得られる試料構造像の分解能は、取得する回折図形の最大回折角で決まり、レンズを使った高分解能像より高い分解能の試料構造像(振幅像と位相像)が得られる可能性がある。この手法はX線で盛んに研究されており、X線分野ではCoherent Diffractive Imaging(コヒーレント回折イメージング)と呼ばれている。電子線分野では、Diffractive Imaging(回折イメージング)、回折顕微法と呼ばれることが多い。カーボンナノチューブなどに応用され0.1nm程度の分解能が得られている。また、結晶に限らず、単一分子など非周期構造の試料にも適用できる。像の再構成には、フーリエ反復位相回復法を用いる。すなわち、試料から得た回折図形の強度の平方根を取って回折振幅とし、ランダムな初期位相を与えてフーリエ変換して試料の近似像を得る。得られた像には、試料外形を超える領域にも構造が現れる。試料外形がはっきり決められる場合はその領域以外の強度を0とおいて(実空間拘束条件)、(試料の外形を正確に決めにくいときは試料より少し大きな領域(サポートと呼ぶ)を規定し、サポートを超えた領域の強度を0とおいて)、これを逆フーリエ変換して回折図形を得る。得られた回折強度が実験値と不一致の場合は、回折振幅を実験値に置き換えて(逆空間拘束条件)、再びフーリエ変換して実像を得る。このような操作を繰り返すことで徐々に正しい位相を回復して、試料の真の構造像が得られる。正しい位相が回復されるまでの反復回数は数1000回以上である。得られる像の精度には、回折図形に含まれる原点まわりの非弾性散乱、検出系や電気回路のノイズ、サポート形状などが影響する。回折図形を取得する際、試料面積(サポート)の2倍以上の領域にビームを照射する。これは回折図形を2倍に細かい間隔でサンプリングすることに対応しており、試料に含まれるすべての情報を取り出すことができ、オーバーサンプリング条件と呼ばれている。実験においては、再構成する対象試料の周囲に試料が存在しない領域を作りだし、オーバーサンプリング条件を満たすように回折図形を記録する必要がある。

    Diffractive imaging⇒

    "Diffractive imaging" is a method to reconstruct a structure image of a specimen from a diffraction pattern of the specimen. Since the diffraction pattern is less influenced by lens aberrations, the resolution of the structure image obtained is determined by the maximum diffraction angle of the diffraction pattern, thus a higher-resolution structure image (amplitude image and phase image) than a HREM image (taken by using lenses) can be obtained. This method has actively been studied in the field of X-ray diffractometry, the method being called "Coherent Diffractive Imaging." In electron microscopy, the method is called "Diffractive Imaging" or "Diffractive Microscopy." The method has been applied to carbon nanotubes, etc., and a spatial resolution around 0.1 nm has been obtained. In addition, the method can be applied to not only crystals but also non-periodic structure specimens such as a single-molecule specimen. To reconstruct the image, the Fourier repetitive phase recovery method is used. That is, the magnitudes of the diffraction amplitudes are calculated by the square root of the diffraction intensities taken from a specimen, and random initial phases are given to the diffraction amplitudes. Then, the diffraction amplitudes with the phases are Fourier-transformed to obtain an approximate structure image. The obtained image exhibits structures even in areas exceeding the specimen area from which the diffraction pattern was taken. When the external shape of the specimen is clearly determined, the image intensities from areas except for the external dimension are set to be 0 (zero) (real-space constraint conditions). (On the other hand, when it is difficult to accurately determine the external shape, a specimen area (called "support") that is slightly larger than the external dimension is defined, and the image intensities from areas exceeding the support are set to be 0. Then, the image is inverse-Fourier-transformed to a diffraction pattern. The diffraction amplitudes that do not match the experimental amplitudes are replaced with the experimental values (reciprocal-space constraint conditions), and then Fourier transform is applied again to obtain a structure image. As this procedure is repeated, the true phases of the specimen are gradually recovered and finally, a true structure image of the specimen is obtained. The number of iterations until the recovery of the true phases exceeds several thousands of times. The accuracy of the obtained image is influenced by the parameters such as inelastic scattering contained around the origin of the diffraction pattern, noise from the detection system including its electronic circuits, and the external dimension of the support. It should be noted that when taking the original diffraction pattern, an area of twice the specimen area (support) must be illuminated with an electron beam. This means that the diffraction pattern is sampled with steps twice as small as those corresponding to the original specimen size, enabling us to extract all information contained in the specimen, which is called the over-sampling condition. In an actual experiment, it is needed to create an area where no specimen exists around the specimen and to record a diffraction pattern so as to satisfy the over-sampling condition.


    Conceptual diagram of the Fourier repetitive phase recovery method for diffractive imaging. A crystal structure image of a specimen is retrieved from an experimental diffraction data with a good accuracy by applying Fourier transform to the reciprocal space data and then inverse Fourier transform to the obtained real space data repeatedly with giving constraint conditions at each step. To be precise, 1) First, a wave field in the reciprocal space is created by using the diffraction amplitudes obtained from a diffraction pattern and giving random initial phases to the diffraction amplitudes. 2) The wave field formed in the reciprocal space is Fourier-transformed to an image in the real space. 3) The intensities of the image outside the support area are set to be 0 (zero). 4) The corrected image is inverse Fourier-transformed to a wave field in the reciprocal space. 5) The amplitudes of the wave field are replaced to those of the experimental diffraction pattern. Repetition of this cycle enables us to accurately retrieve the phases of diffraction spots in the reciprocal space and the wave field in the real space. 6) Finally, an accurate structure image of the crystalline specimen is reconstructed.

  • ディフラクトグラムタブロー

    diffractogram tableau


    入射ビームを1~2度位傾け方位角を次々に変えて撮ったアモルファス試料の高倍像のフーリエ変換図形(diffractogram)を、2次元的に表示したもの。Zemlin tableauとも呼ばれる。このtableauに現れる図形の楕円度や対称性を利用して、非点収差(軸上)補正、コマフリー軸合わせ、3回非点収差補正を行う。Rose-HaiderタイプのCsコレクターが電顕に装着されている場合は、球面収差補正、4回非点収差補正、5次の球面収差の最適化を行うことができる。これらの補正を自動的に行うソフトウェアが開発されている。

    Diffractogram tableau ⇒
    図(a)、(b)は、収差補正を施していない場合と施した場合の diffractogram tableau。それぞれの図において、中心には入射電子線の傾斜角が零のdiffractogram 、外側には電子線を傾斜して得たdiffractogramをその傾斜角と方位角に応じて配置している。
     入射電子線を傾斜した場合、軸上(幾何)収差があると、その大きさや対称性によってdiffractogramの形状が円状から歪む。図(a)では、支配的な収差である三次球面収差のために、電子線を傾斜した場合のdiffractogramが円状から大きく変化している。一方、図(b) では、電子線を傾斜しても収差の影響が少なく、diffractogramの形状がいずれも円状に近く、図形間の形状の変化も少ない。

    "Diffractogram tableau," which is also called "Zemlin tableau," displays two-dimensionally Fourier transform patterns of high-magnification images taken from an amorphous thin film while the azimuthal angle is sequentially changed by a sequential tilt of the incident beam (tilt step: 1 to 2°). Utilizing the degrees of ellipse and symmetries of the patterns, axial astigmatism correction, coma-free axis alignment and three-fold astigmatism correction are executed. When a Rose-Haider-type Cs corrector is installed in a TEM, the use of the diffractogram tableau enables us to correct spherical aberration and four-fold astigmatism and optimize fifth-order spherical aberration. Software that automatically executes these corrections has already been developed.
    Diffractogram tableau
    Figs. (a) and (b) show two diffractogram tableaus without Cs correction and with Cs correction, respectively. The diffractogram tableaus are displayed in the following manner. At the center, a diffractogram obtained without tilt of the incident electron is placed, and around the center, the diffractograms obtained by tilting the incident electron beam are placed according to the tilt angles and azimuth angles.
    When the incident beam is tilted, the shapes of the diffractograms are distorted depending on the magnitudes and symmetries of the axial (geometrical) aberrations. In Fig. (a), each diffractogram for the tilted electron beam is largely distorted from a perfect circle, which is caused mainly by the third-order spherical aberration. In Fig. (b), the diffractograms taken at the tilted incident beams keep almost circular shape and show small difference between the patterns of the diffractograms, indicating the aberrations being almost corrected.

  • ディンプルグラインダ

    dimple grinder



    "Dimple grinder" is a mechanical polishing device. It creates a dimple (dip) with a thickness down to 10 μm or less on a parallel plate specimen prepared by polishing using a rotational polishing device (thickness: 100 μm or less). It uses a polishing agent, such as corundum particles having different particle sizes (0.1 μm to several μm). The specimen with the dimple is further thinned by ion milling.

  • デコンボリューション




    "Deconvolution" is a method to eliminate spectral blur due to an instrument function. An observed spectrum is given by the convolution of a true spectrum and an instrument function. Fourier transform of the observed spectrum is expressed by the product of the Fourier transform of the true spectrum and the Fourier transform of the instrument function. Thus, the resultant Fourier transform of the true spectrum is obtained by dividing the Fourier transform of the observed spectrum by the Fourier transform of the instrument function. Then, the true spectrum is obtained by the inverse Fourier transform of the obtained Fourier transform of the true spectrum. The deconvolution method is used by combining the Fourier-log method, the maximum entropy method (MEM) or the Richardson-Lucy method.

  • デスキャン





    De-scan means to bring the electron beam deflected from the optical axis back to the optical axis using a two-stage deflector coil, the deflection being caused by illumination position or illumination angle of the incident electron beam onto a specimen. De-scan is applied mainly to the following two cases.

    1) When the incident electron beam is scanned over a wide area of a specimen, the electron beam can stray off the optical axis at the peripheral part of the scanned area. Then, the incidence position or the incidence angle of the electron beam to a STEM or EELS detector whose center is adjusted to the optical axis deviates from the axis.
    In the case of STEM; if an electron beam passing through a scan point of the specimen deviates from the STEM detector, the STEM image intensity is varied compared with the correct intensity which should be detected.
    In the case of EELS; if an electron beam passing through a scan point of the specimen does not run on the center of the EELS detector or runs obliquely to the optical axis of the detector, the energy value of the EELS spectrum cannot be correctly measured.
    To avoid such an undesirable electron-beam position or angle to the STEM or EELS detector, a two-stage deflector coil in the image-forming lens system is operated synchronously with the beam scan to always bring back the electron beam to the center of the detector and/or parallel to the optical axis.
    2) In the case of precession electron diffraction, to precess the incident electron beam onto a certain point on a specimen, a two-stage deflector coil in the illumination lens system is used. The first deflector coil tilts the incident electron beam to a certain angle (up to approximately 5°), and then the second deflector coil compensates the displacement of the tilted incident electron beam from the optical axis. Then, the electron beam passing through the specimen runs oblique to the optical axis. A two-stage defector coil in the image-forming lens system is used to bring back the electron beam to run on the optical axis. A precession diffraction pattern is obtained by such operation of the two-stage defector coils.  

  • デッドタイム

    dead time



    "Dead time" is the required time interval between the measuring equipment receiving one signal and this equipment being able to accept the next signal.

  • デバイシェラー環

    Debye-Scherrer ring



    "Debye-Scherrer rings" are concentric diffraction rings produced by Bragg reflections, which are obtained when polycrystalline thin films are illuminated with a highly parallel electron beam.

  • デバイワラー因子(温度因子)

    Debye-Waller factor



    A factor that expresses an effect of thermal vibrations (lattice vibrations) of atoms. The intensity of Bragg reflections at high angles is damped by the "Debye-Waller factor."

  • デルタフリンジ

    δ fringe



    "δ fringe" means a fringe contrast, which is observed in bright- and dark-field images under a two-beam approximation condition in the case where the orientations of the upper and lower crystals are different to each other (for example, twin boundary) at an interface oblique to the surface of a crystalline specimen. The fringe contrast, which appears at two positions (edges) where the interface intersects the upper and lower surfaces, exhibits symmetric contrast in the dark-field and anti-symmetric contrast in the bright-field with respect to the center of the fringe (specimen).

  • 電圧軸

    accelerating (acceleration) voltage center



    When fluctuations are added to accelerating voltage using a high-tension wobbler, a TEM image spirally enlarges and shrinks. The center of this enlargement and shrinkage is called "accelerating (acceleration) voltage center." Alignment of the accelerating voltage center is carried out to bring the accelerating voltage center to the center of the fluorescent screen for viewing the image by the use of a double-deflection coil system. Since the fluctuations of the high voltage are small (<10-6), this alignment is used to minimize the effect of energy spread due to inelastic scattering (plasmon scattering) in a specimen rather than the effect of high-voltage fluctuations. This alignment is required when taking images at a medium magnification lower than 100,000×.

  • 電解研磨

    electrolytic polishing



    "Electrolytic polishing" is a technique used for preparing a thin film on metal, alloy, etc. In this technique, a specimen (acting as an anode) and a platinum (Pt) plate or a stainless-steel (acting as a cathode) are immersed in a suitable electrolyte solvent. Then, an electrostatic potential is applied between these electrodes to elute the atoms of the specimen surface, and finally the specimen surface is thinned with its surface kept smooth. The advantage of electrolytic polishing is that a thinned specimen can be prepared with no mechanical stress.

  • 電界引き出し

    field extraction



    "Field extraction" is a technique to extract electrons in a solid to the outside without heating the solid, by applying a strong electric field (107 V/cm or more) to the surface of the solid.

  • 電界放出

    field emission



    "Field emission" is a technique to emit electrons from the tip of the cathode. A sharpened cathode made of a material (normally, tungsten) that has an appropriate work function is placed in a strong electric field produced by the extraction electrode to emit electrons from the cathode tip.

  • 電界放出型電子銃

    FEG field-emission electron gun



    There are two types of field-emission electron gun (FEG); the cold cathode type and the thermal (thermally assisted) type. The FEG emits electrons from a sharpened tip of a cathode by applying a strong electric field. Compared with the thermionic-emission electron gun, the beam current of the FEG is small but its brightness is as high as 107 to 108. The FEG produces a small electron probe with a small energy spread. The FEG is essential for electron holography.

  • 電解めっき

    electrolytic plating



    "Electrolytic plating" is a technique to form a thin metal layer on a surface of a solid specimen by electrolysis of a conductive solid (ex. metal) in a suitable electrolyte solvent. Actually, a specimen (acting as an anode) and a platinum (Pt) plate or a stainless-steel (acting as a cathode) are immersed in a suitable electrolyte solvent. By the flow of electric current between these electrodes, the eluted Pt or stainless-steel is deposited on the specimen surface.

  • 電荷・軌道秩序

    charge and orbital ordering



    "Charge and orbital ordering" states the charge-ordered state and the orbital-ordered state for 3d electrons in transition metals in a crystal. The charge-ordered state means that two charge states are alternately and regularly arranged. The orbital-ordered state means that orbitals, for example eg orbitals, with one orientation and the other orientation are alternately and regularly arranged. These states emerge in perovskite oxides containing transition metals when composition or temperature is changed. Such super structures in electronic systems are reflected in lattice systems, thus these structures are observed by superlattice reflections in an electron diffraction pattern.

  • 電源同期

    Line synchronization



    "Line synchronization" means a synchronization of the timing to start electron-beam scan in each horizontal direction with the phase of the AC power wave when acquiring a STEM image. When the line synchronization function is operated at the image acquisition, the influence of external disturbance with the frequency (or the multiples of the frequency) of the AC power-source becomes same on every scan line, and then the external disturbance happening in each scan line apparently disappears. As a result, the fine noise in the horizontal scan line disappears, and the influence of the external disturbance is reduced from the STEM image.