Bend‐contour patterns are used to investigate the structure features of crystals of hexagonal selenium and tellurium grown in thin amorphous condensates of Se, SeTe, CuTe. The results are compared with microinterferometry data. Two bend effects are revealed: a hitherto unknown continuous bending, progressing with crystal growth of the lattice about the c‐axis (360° rotation over a distance of 3 to 8 μm) and buckling of a thin‐film crystal as a whole. The buckling is explained with the help of the following model: the build‐up of the crystal lattice is accompanied by the formation of an abnormally large number of vacancy growth defects conditioned by crystallization from the amorphous state. As the excess vacancies emerge at the surface there arise compressive stresses developed by the amorphous film.
The relationship between bend—contour patterns in electron micrographs and sample crystallography, buckling, and orientation is examined in the case of cylindrical bending. The principles, determining the structure of extinction contour patterns (sequence, spacing), with the bend axis deflected from the perpendicular direction to the electron beam and the reciprocal lattice plane (which provides the observed reflections) deflected from the film plane, are set forth. Relationships between the bending radius and the contour spacing, from which earlier known formulae may be derived as a particular case, are established. The established principles are demonstrated on thinfilm hexagonal selenium crystals and may serve as a basis for the study of more complex cases of bending.
Bend‐contour pattern analysis is used to study processes occurring in initially dislocation‐free selenium crystals during the formation of subgrain boundaries in the course of crystal growth. Using the data obtained on the magnitude and character of lattice disorientations in various types of emerging boundaries, a block‐formation model is proposed. The model is based on the possible modes of relaxation of the crystal lattice elastic bending, inherent in crystals growing in an amorphous film.
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