First-principles spin-density calculations were made of the Si vacancy, VSi, in 3C- and 2H-type samples, in all of its possible charge states. The calculated electronic structure revealed the presence of a stable spin-aligned electron-state near to the mid-gap. The neutral and doubly-negative charge states of VSi in 3C-material were stabilized in a high-spin configuration, with S = 1, which gave rise to a ground state that was a many-electron orbital singlet. In the case of singly negative VSi, a high-spin ground-state was found with S = 3/2. In the high-spin configuration, VSi preserved the Td symmetry. The results indicated that the ground state of VSi had a low-spin configuration.

Silicon Vacancy in SiC. L.Torpo, R.M.Nieminen, K.E.Laasonen, S.Pöykkö: Applied Physics Letters, 1999, 74[2], 221-3