Superscrew dislocation contrast on synchrotron white-beam topographs: an accurate description of the direct dislocation image

A kinematic (geometrical) diffraction simulation model has been developed t o provide understanding of direct dislocation images on synchrotron white-b eam X-ray topographs, and has been successfully applied to illustrate the c ontrast formation mechanisms involved in images of micropipe-related supers crew dislocations in silicon carbide crystals. The coincidence of the simul ations with the contrast features of the superscrew dislocation images, rec orded using a series of synchrotron topography techniques, shows that this model is capable of revealing the detailed diffraction behavior of the high ly distorted region around the dislocation core and determining the quantit ative characteristics of the dislocations. The simulation technique is thus demonstrated to be a simple but efficient method for interpretation of syn chrotron topographs, and may be applied to explain the topographic contrast characters of general crystal defects.