Optical microscopic and atomic force microscopic observations of a Lely platelet revealed a macro-step pattern whose periodicity suggested that it possessed a structure with a repeat distance that was some 350 times the bilayer thickness. Transmission Laue patterns revealed a 3-fold symmetrical pattern which was qualitatively similar to that obtained from the 6H structure, but which involved a huge number of closely-spaced reflections. The spacing of the diffraction spots in the 10•l row indicated that the polytype of the specimen was 540R. Synchrotron white-beam X-ray topography revealed the presence of growth dislocations which were directed towards the growth facets of the platelet. There were also deformation-induced basal-plane dislocations, and a group of super-screw dislocations which were close to the nucleation point of the crystal. Optical microscopy revealed the presence of micropipes which were related to the above super-screw images. Calculations indicated that the total of the Burgers vectors of the observed micropipes was between 100 and 200nm. Trails of basal-plane dislocation etch-pits were shown, by Nomarski microscopy, to intersect the etched crystal surface in a roughly periodic fashion. These trails were attributed to enhanced etching of the intersection, across a 1º surface tilt, of a series of basal-plane dislocations which were distributed along the crystallographic c-axis with a periodicity that was related to that of the stepped ledges of the crystal surface. Atomic force microscopy revealed a higher etching rate at the intersections of basal-plane dislocations at the ledges.

Synchrotron White Beam X-Ray Topography and Atomic Force Microscopy Studies of a 540R-SiC Lely Platelet W.M.Vetter, M.Dudley, W.Huang, P.Neudeck, J.A.Powell: Materials Science Forum, 2000, 338-342, 469-72