電子回折

electron diffraction

[目次：理論(電子の散乱／回折／結像)]

試料に電子線を照射し、得られる回折図形から結晶構造の情報を得る手法。試料が結晶のときは、原子配列の周期性、対称性、規則性、結晶格子の完全性からの乱れなどの結晶構造についての情報が得られる。試料が非晶質の場合には第一、第二 ．．．近接原子の距離や個数などがわかる。電子回折図形の幾何学的解析には、運動学的回折（X線回折で用いられる）が適用できるが、強度の定量的解析には動力学的回折を適用する必要がある。電子線はX線よりビームを細くできるので、局所領域からの結晶構造情報を得ることができる。

A method for obtaining information on crystal structures from diffraction patterns, acquired by electron-beam illumination on a specimen. When a specimen is a crystal, the information on various crystal structures is obtained, which include periodicities, symmetries and ordering of atomic arrangements, and defects of crystal lattices. When a specimen is an amorphous material, the distances between the first, second, ... nearest neighbor atoms and the number of these atoms are obtained. Kinematical diffraction theory, which is used for X-ray diffraction, can be applied in geometrical analysis of electron diffraction patterns. However, dynamical diffraction theory needs to be applied in quantitative analysis of diffraction intensities. Since the electron beam is much sharper than the X-ray beam, electron diffraction enables us to obtain crystallographic information on local areas.

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