Grazing-incidence synchrotron white beam X-ray topography images of closed-core threading screw dislocations in 4H-SiC appeared as roughly elliptically shaped white features, with an asymmetric perimeter of dark contrast which was greatly enhanced on one side or other of the g vector. Ray-tracing simulations indicate that the relative position of the enhanced dark contrast feature revealed the sense of the closed-core screw dislocation. Dislocation senses so obtained were validated using back-reflection images recorded with small Bragg angle. Therefore, the sense of the closed-core threading screw dislocations could be unambiguously revealed using either grazing-incidence or so-called small Bragg angle back-reflection synchrotron white-beam X-ray topography.

Direct Determination of Dislocation Sense of Closed-Core Threading Screw Dislocations Using Synchrotron White Beam X-Ray Topography in 4H Silicon Carbide. Y.Chen, M.Dudley: Applied Physics Letters, 2007, 91[14], 141918