Molecular dynamics and quasidynamics simulations of the annealing of bulk and near-surface interstitials formed in molecular-beam epitaxial Si due to low-energy particle bombardment during deposition

Molecular dynamics and quasidynamics simulations, utilizing the Tersoff many-body potential, were used to investigate the relaxation, diffusion, and annihilation of split and hexagonal interstitials resulting from 10 eV Si irradiation of (2x 1)-terminated Si(001). The interstitials were created in layers two through six. Stable atomic configurations and total potential energies were derived as a function of site symmetry and layer depth. The interstitial Si atoms were allowed to diffuse and total potential energy changes calculated. Lattice configurations along each path, as well as the starting configurations, were relaxed and minimum energy diffusion paths derived. The results showed that the minimum energy paths were toward the surface and generally involved tetrahedral sites. Calculated interstital migration activation energies were always less than 1.4 eV and were much lower in the near-surface region than in the bulk. Thus, the defects could easily be annealed out over time periods corresponding to less than that required for monolayer deposition under typical molecular-beam epitaxial film growth conditions.