Neutral and negatively charged silicon vacancies in neutron irradiated SiC: a high-field electron paramagnetic resonance study

High-field pulsed and continuous-wave electron paramagnetic resonance (EPR) techniques at 95 GHz have been used to investigate radiation defects in neutron-irradiated SiC. In the temperature range between 1.2 and 300 K three types of EPR spectra were observed in 4H-and 6H-SiC crystals that are attributed to the neutral silicon vacancy, the negatively charged silicon vacancy, and the carbon vacancy. In the EPR spectra of V-Si(-) in 4H- and 6H-SiC an anisotropic splitting si of the EPR lines is observed. This splitting is assumed to arise from small differences in the g-tensor of the quasi-cubic (k) and hexagonal (h) sites. The g-factor for the k site g (k) is found to be isotropic with g(k) = 2.0032 and the g-factor of the h-site is found to be slightly anisotropic with g (h) = g(k) - 0.00004 and g perpendicular to (h) = g(k) - 0.00002. The 95 GHz EPR spectra at 1.4 K show that the ground state of V-Si(0) is a triplet state. Additional 9.5 GHz EPR experiments reveal signals that are attributed to the carbon vacancy on the basis of the observed hyperfine splitting. The results demonstrate that V-Si,(-) V-Si(0) and V-c are dominant defects after neutron irradiation of SiC to doses up to 10(19)cm(-2). (C) 2001 Elsevier Science B.V. All rights reserved.