Identification of a Frenkel-pair defect in electron-irradiated 3C SiC

An electron paramagnetic resonance (EPR) spectrum labeled LE1 was observed in n-type 3C SiC after electron irradiation at low temperatures (similar to 80-100 K). A hyperfine interaction with four nearest C neighbors similar to that of the well-known silicon vacancy in the negative charge state was observed, but the LE1 center has a lower symmetry, C-2v. Supercell calculations of different configurations of silicon vacancy-interstitial Frenkel-pairs, V-Si-Si-i, were performed showing that pairs with a nearest neighbor Si interstitial are unstable-V-Si and Si-i will automatically recombine-whereas pairs with a second neighbor Sii are stable. Comparing the data obtained from EPR and supercell calculations, the LE1 center is assigned to the Frenkel-pair between V-Si and a second neighbor Sii interstitial along the [100] direction in the 3+ charge state, V-Si(-)-Si-i(4+). In addition, a path for the migration of Si-i(4+) was found in 3C SiC. In samples irradiated at low temperatures, the LE1 Frenkel-pair was found to be the dominating defect whereas EPR signals of single vacancies were not detected. The center disappears after warming up the samples to room temperature.