First-principles calculations were made of the atomic and electronic structures of neutral and charged C and Si vacancies in 3C- and 4H-type material. It was demonstrated that the principal properties of the vacancies depended only weakly upon the polytypes involved. In both polytypes, the formation of C vacancies was accompanied by a significant symmetry-breaking distortion of the neighbouring Si atoms. A negative-U behaviour was also predicted for the C vacancy. In the case of Si vacancies, only an outward breathing relaxation of the neighbouring C atoms occurred. High-spin states were found for the Si vacancies, whereas low-spin states were predicted for C vacancies.

Monovacancies in 3C and 4H SiC. J.Furthmüller, A.Zywietz, F.Bechstedt: Materials Science and Engineering B, 1999, 61-62, 244-7