Experimental evidence for a dual vacancy–interstitial mechanism of self-diffusion in silicon

Epitaxially grown isotopically enriched Si layers have been used to study self-diffusion in Si directly at the temperatures of 1000 and 1100 °C. We obtain equilibrium diffusion coefficients in accordance with previous experiments and theoretical calculations. Comparison of diffusion data of self-, antimony, and phosphorus diffusion in Si under identical conditions of perturbed self-interstitial and vacancy concentrations created by surface reactions enables us to determine the microscopic mechanisms of Si self-diffusion. We find that, in this temperature range, self-interstitials contribute roughly $\text{2/3}$ to Si self-diffusion, and vacancies $\text{1/3,}$ with the concerted exchange component being less than 14%. This constitutes direct experimental evidence that, on the atomic scale, self-diffusion in Si is mediated both by self-interstitials and vacancies.