Electron diffraction effects in silicon carbide. I. Pure polytypes. II. whiskers

Pure samples of the three most common hexagonal SiC polytypes have been examined in transmission electron diffraction. The diffraction patterns from the most densely populated planes in reciprocal space, the (h0l)* planes, differ considerably from the calculated patterns. The difference can be attributed to ubiquitous multiple diffraction. Calculated intensity distributions for 100 kV electrons are given for 4H, 6H, and 15R SiC. SiC whiskers have also been examined, and the unusual diffraction effects seen can, in general, be explained as a combination of (a) extreme disorder, (b) distorted lattices and (c) multiple diffraction.