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 degreesC and 872 degreesC for various times and proton fluxes. Detailed modeling of RESD provides direct evidence that vacancies at high temperatures diffuse with a migration enthalpy of H-V(m)=(1.8+/-0.5) eV significantly more slowly than expected from their diffusion at low temperatures, which is described by H-V(m)<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.