Radiation enhanced silicon self-diffusion and the silicon vacancy at high temperatures

We report proton radiation enhanced self-diffusion (RESD) studies on Si-isotope heterostructures. Self-diffusion experiments under irradiation were performed at temperatures between 780 0C and 872 0C for various times and proton fluxes. Detailed modeling of RESD provides direct evidence that vacancies at high temperatures diffuse with a migration enthalpy of HmV = (1.8±0.5 eV) significantly more slowly than expected from their diffusion at low temperatures, which is described by HmV < 0.5 eV. We conclude that this diffusion behavior is a consequence of the microscopic configuration of the vacancy whose entropy and enthalpy of migration increase with increasing temperature.