The Simulation of Bragg-Case Section Images οf Dislocations and Inclusions in Aspect of Identification of Defects in SiC Crystals

Abstract

The numerical simulation has been applied for studying of Bragg-case section topographic images of dislocation and rod-like inclusions. The validity of simple approximation of extinction contrast was confirmed in the case of screw dislocations in silicon carbide crystals. A procedure for approximate calculation of the strain field of rod-like inclusion was constructed, consisting of adding the contributions from a very large number of point-like inclusions uniformly distributed inside the assumed volume of the inclusion. The procedure ensured a reasonable similarity between the simulated topographs and experimental Bragg-case section topographic images of some pipe-formed cavities in silicon carbide crystals. The method is useful for some other materials, e.g. it enabled to compute realistic simulation of plane-wave topographs of the rod-like inclusions in YAG.

Contrast in transmission X-ray diffraction topographs of growth defects in the core of SrLaGaO4single crystals

“…More exact calculations of the contrast of defects are in the general case difficult in view of the complicated description of the deformation field. Some successful attempts to simulate the contrast of rod-like defects for Bragg-case topographs were described by Wierzchowski et al (2010) and Balcer et al (2010) using the approximation of these defects as a sum of contributions from uniformly distributed point inclusions. The use of the method in the transmission case will be the subject of further investigations.…”

X-ray topographic investigation of the deformation field around spots irradiated by FLASH single pulses

“…It may be noticed that the craters cause some bending of the interference fringes, and some parts of the images overlap. It was possible to obtain a reasonable similarity of the presently recorded section images of some spots, corresponding to the higher energy of the FLASH radiation, to the numerically simulated images of the rod-like defects using recently developed numerical procedure described in Balcer et al (2010).…”

“…It was indicated (Balcer et al, 2010) that the contours of the effective change of reflecting condition (i.e. the resulting change of Bragg angle caused by the change of orientation and the change of the lattice spacing) computed by the composed procedure retain an axial character of the obtained field with the change of the sign along the reflecting planes and provide almost a constant value of the strain inside the inclusion.…”