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Dislocation contrast on X-ray topographs under weak diffraction conditions
Journal of Applied Crystallography  (IF3.304),  Pub Date : 2021-07-30, DOI: 10.1107/s1600576721006592
Hongyu Peng, Tuerxun Ailihumaer, Yafei Liu, Balaji Raghotharmachar, Xianrong Huang, Lahsen Assoufid, Michael Dudley

The contrast of dislocations in 4H-SiC crystals shows distinctive features on grazing-incidence X-ray topographs for diffraction at different positions on the operative rocking curve. Ray-tracing simulations have previously been successfully applied to describe the dislocation contrast at the peak of a rocking curve.The present work shows that the dislocation images observed under weak diffraction conditions can also be simulated using the ray-tracing method. These simulations indicate that the contrast of the dislocations is dominated by orientation contrast. Analysis of the effective misorientation reveals that the dislocation contrast in weak-beam topography is more sensitive to the local lattice distortion, consequently enabling information to be obtained on the dislocation sense which cannot be obtained from the peak.