Insertion and diffusion of helium in cubic SiC were investigated by means of density functional theory. The method was assessed by calculating relevant properties for the perfect crystal along with point defect formation energies. Results were consistent with available theoretical and experimental data. Helium insertion energies were calculated to be lower for divacancy and Si vacancy defects compared to the other mono-vacancies and interstitial sites considered. Migration barriers for helium were determined by using the nudged elastic band method. Calculated activation energies for migration in and around vacancies (silicon vacancy, C vacancy or divacancy) range from 0.6 to 1.0eV. Activation energy for interstitial migration was calculated to be 2.5eV. Those values were related to recent experimental activation energies for migration that range from 1.1 to 3.2eV; depending upon the SiC samples used and on helium implantation conditions.

Theoretical Study of Helium Insertion and Diffusion in 3C-SiC. R.M.Van Ginhoven, A.Chartier, C.Meis, W.J.Weber, L.R.Corrales: Journal of Nuclear Materials, 2006, 348[1-2], 51-9