Planar Orbital Method for Surface Electronic Structures

Abstract

The method is applied to the self-consistent electronic structural calculations of the Si(001) 2 x 1 surface with symmetric and buckled dimers, As/Si(001) 2 x 1 and Sb/Si(001) 2 x 1 surfaces with symmetric dimers, and the hydrogen-passivated Si(001) 2 x 1 surface, as well as the reflectance-difference spectra of Si(001) 2 x 1 and 2 x 2 surfaces. The calculating work function of Si(001) 2 x 1 surface supports the buckled dimer model. For the As/Si(001) surface, we find substantial charge transfer, indicating a strong ionic character in the As-Si bonds. And the strong polar covalent bonding between surface As atoms and underlying Si atoms may be responsible for the stability of the As/Si(001) surface. A pathway was found for the desorption of H2 molecules from the Si(001) 2 x 1 surface in which the activation energy barrier is negligible and the desorption energy is approximately 60 kcal/mol, in agreement with experimental findings.