Electronic structure and total-energy migration barriers of silicon self-interstitials

Pseudopotential density-functional calculations have been performed on silicon self-interstitial supercell model geometries to yield extensive information on electronic states. We present band structures, charge densities, and densities of states to identify and characterize electronic states associated with silicon self-interstitials in the geometries studied. Total energies obtained yield migration barriers for both Si⁽⁰⁾ and Si⁽²⁺⁾ interstitials. We also present the results of preliminary total-energy relaxation studies and show their effects on electronic states and total-energy calculations, demonstrating the importance of relaxation in determining migration barriers. Electron-assisted migration is shown to occur, thus solving the mystery of the disappearing self-interstitial and providing an initial understanding of migration in low-temperature irradiated silicon.