Defect structure and polytypism in silicon carbide

Abstract

The mechanics of crystal growth of silicon carbide from chromium solution are shown to be strongly temperature dependent. Specific changes in the dislocation morphology are found to reflect the temperature dependence, which itself may be related directly to the fact that SiC dissolves in chromium in an aggregated state. The degree of aggregation varies with temperature. Electron microscopy has revealed that dislocations in SiC are dissociated and that the stacking faults may act as nucleation centers for growth of a ‘new’ polytype. Cubic β SiC was found to grow from basal plane stacking faults in 6H, αSiC. A model is advanced, based upon a proposed temperature dependence of the relative stacking fault energies of zincblende and wurtzite stacking in SiC, in an attempt to explain heterogeneous nucleation of the SiC polytypes.