An investigation was made of radiation-induced defects in neutron-irradiated and subsequently annealed 6H-SiC using electron paramagnetic resonance, magnetic circular dichroism of absorption, and magnetic circular dichroism of absorption-detected electron paramagnetic resonance methods. In samples which were annealed beyond the annealing temperature of the isolated Si vacancy photo-induced electron paramagnetic resonance spectra of spin S = 1 centers that occur in orientations expected for nearest neighbor pair defects were observed. electron paramagnetic resonance spectra of the defect on the 3 inequivalent lattice sites were resolved and attributed to optical transitions between photon energies of 0.999 and 1.075eV by magnetic circular dichroism of absorption-detected electron paramagnetic resonance. The resolved hyperfine structure indicated the presence of one single C nucleus and several Si ligand nuclei. These experimental findings were interpreted with help of total energy and spin density data obtained from the standard local-spin density approximation of the density-functional theory, using relaxed defect geometries obtained from the self-consistent charge density-functional theory based tight binding scheme. Several defect models were compared, among which only the photo-excited spin triplet state of the C-antisite – C-vacancy pair in the doubly-positive charge state could explain all of the experimental findings. It was proposed that the (CSi-VC) defect was formed from the isolated Si vacancy as an annealing product by the movement of a C neighbor into the vacancy.

Structure of the Silicon Vacancy in 6H-SiC after Annealing Identified as the Carbon Vacancy–Carbon Antisite Pair. T.Lingner, S.Greulich-Weber, J.M.Spaeth, U.Gerstmann, E.Rauls, Z.Hajnal, T.Frauenheim, H.Overhof: Physical Review B, 2001, 64[24], 245212 (10pp)