Silicon self-diffusion in isotope heterostructures

Self-diffusion of silicon is measured between 855 and 1388 degrees C in highly isotopically enriched Si-28 layers. The profiles of Si-29 and Si-30 are determined by secondary ion mass spectrometry. Temperature dependence of the self-diffusion coefficients is accurately described over seven orders of magnitude with one diffusion enthalpy of 4.75 eV. This single enthalpy indicates that self-interstitials dominate self-diffusion. The high accuracy of our data enables us to estimate an upper bound for the vacancy-assisted diffusion enthalpy of 4.14 eV, which agrees with recent theoretical calculations.