Unidirectional Formation of Tetrahedral Voids in Irradiated Silicon Carbide

Abstract

After high-dose, high temperature fast neutron irradiation, near-tetrahedral voids bounded with {111} surfaces were observed in beta-SiC. This was unexpected as the surface-to-volume ratio is larger than {111} octahedral voids common in both metals and ceramics. To obtain additional insight, three-dimensional structure of the tetrahedral voids was studied by transmission electron microscopy. Interestingly, only one half of {111} family planes in the zinc blende structure were permitted as void surfaces. The result is that the tetrahedral voids were oriented in only one of two possible directions, indicating that all void faces are either Si- or C-terminated polar surfaces.