AVS 47th International Symposium
    Surface Science Monday Sessions
       Session SS3-MoA

Paper SS3-MoA9
First-Principles Study of Vacancy Ionization Effects on Surface Diffusion

Monday, October 2, 2000, 4:40 pm, Room 210

Session: Surface Diffusion and Wetting
Presenter: H.Y.H. Chan, University of Illinois, Urbana-Champaign
Authors: H.Y.H. Chan, University of Illinois, Urbana-Champaign
E.G. Seebauer, University of Illinois, Urbana-Champaign
Correspondent: Click to Email
While the effects of charged point defects on diffusion in bulk semiconductors have been studied extensively for many years, such phenomena have received almost no attention in connection with diffusion on surfaces. Recent studies in our laboratory using second harmonic microscopy (SHM) on Si have strongly suggested that charged vacancies can significantly affect observed activation energies and prefactors in a manner analogous to that observed for bulk diffusion. Furthermore, these studies have revealed significant non-thermal effects of photon illumination that also appear to be mediated by charged vacancies. Unfortunately, a more quantitative and complete description of these various phenomena requires a knowledge of the energy levels of the various surface vacancy charge states. Until now these energy levels have remained unknown on Si. We report herein the results of density-functional-theory based quantum calculations that fill this gap. Total-energy calculations using a plane-wave/pseudopotential approach within the local-density approximation were used to determine the charge-state dependent formation energies of vacancies as a function of Fermi level. The computed electronic structure, lattice reconstruction, and their effects on surface diffusion are discussed.