等傾角干渉縞

bend contour (equal inclination fringe)

[目次：理論(電子の散乱／回折／結像)]

試料結晶に湾曲があると、ブラッグ条件を丁度満たす場所が暗視野像に強い強度を与え、明るく見える。明視野像は暗視野像と相補的に暗くなる。入射波に対して結晶が等しい傾きの場所は等しい強度を与えるので、全体として(曲)線状のコントラストを生ずる。これを等傾角干渉縞という。結晶性試料の湾曲の様子がわかる。 なお、一つの反射だけが強く励起され動力学効果が強い場合には、一本の主極大の線だけでなく弱い副極大の線も観察される。

When a crystalline specimen is bent, the dark-field image of the specimen shows strong intensities at positions where a Bragg condition is satisfied, thus the positions being seen to be bright. The bright-field image of the positions is complementarily dark. Since the crystallographic orientation of the positions is equal with respect to the incident beam, they give an equal intensity. The intensity contours are termed equal inclination fringes or bend contours. The bend contours reveal the bend feature of a crystalline specimen. It should be noted that if only one reflection is strongly excited, not only the principal maximum line but also subsidiary maxima lines appear due to a strong dynamical effect.

TEM images of bend contours in a mica taken at an accelerating voltage of 200 kV.
(a)Bright-field image.
(b), (c), (d), (e) and (f) Dark-field images formed by reflections indicated in diffraction pattern (g).
(g)Diffraction pattern acquired from the same field.

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