Arsenic atom location on passivated silicon (111) surfaces

Abstract

The position of As atoms on a clean Si(111) surface has been determined with x-ray standing waves in ultrahigh vacuum. The As atoms occupy exclusively the top half of the silicon (111) double plane and lie at 0.17 Å above the unrelaxed bulk terminated silicon (111) plane. This value is in good agreement with recent total-energy minimization calculations. A significant but limited stability of As passivated surfaces is observed upon exposure to various ambients. We also present general arguments showing how surface specificity can be achieved with x-ray standing-wave measurements such as the above, where bulk-symmetry site-occupancy rules are broken.