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Kinematical theory of images from polycrystalline and random‐network structures
Author(s) -
Krivanek O. L.,
Howie A.
Publication year - 1975
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889875010254
Subject(s) - crystallite , amorphous solid , polk , speckle pattern , optics , field (mathematics) , condensed matter physics , physics , materials science , crystallography , mathematics , chemistry , biochemistry , pure mathematics
Kinematical electron microscope images to be expected from the Polk continuous random‐network model and from a polycrystalline cluster have been computed. Dark‐field images of both models show qualitatively similar speckle patterns. Fringes are observed in bright‐field images of thin polycrystals ( t ≲ 40Å), but they disappear in thicker samples and are not observed in any of the Polk‐model images. The experimental observation of fringes therefore cannot be explained by the current theory, possibly because it does not take account of the angular spread of illumination. Except perhaps in very thin specimens, it seems impossible at present to draw any reliable conclusions about the local atomic arrangement in amorphous materials by simple examination of electron micrographs.