Dislocation microstructure of 4H–SiC single crystals plastically deformed around the transition temperature

Abstract

4H–SiC specimens were plastically deformed by basal slip at temperatures between 800 °C and 1300 °C. Samples were investigated by means of transmission electron microscopy and high-resolution techniques. The accepted transition temperature (1030 °C) was found not to be actually so well defined since the two mechanisms were operating together between 1000 °C and 1100 °C. Dissociation of basal dislocations takes place over the entire temperature range investigated, having a different influence on each regime. In the high temperature regime, after dissociation the two partials slip together in the basal plane fringing a stacking fault. We have determined the dissociation width, obtaining a stacking fault energy of 20 ± 5 mJ/m2. However, below the transition temperature the difference in mobility of the partials and the low stacking fault energy allow the leading partial to glide alone. We discuss the consequences of this finding for the crystal structure (cubic bands nucleation) and mechanical behaviour (high work-hardening rate).