The nature and strength of the bonding forces between two II-passivated Si surfaces are studied with the density-functional theory, using an approach based on recent theoretical advances in understanding of van der Waals forces between two surfaces. Contrary to previous suggestions of van der Waals attraction between H overlayers, we find that the attraction is mainly due to long-range van der Waals interactions between the Si substrates, while the equilibrium separation is determined by short-range repulsion between occupied Si-H orbitals. Estimated bonding energies and Si-H frequency shifts are in qualitative agreement with experiment. [S0163-1829(98)06448-0].
Bibliographical noteCopyright (1998) by the American Physical Society.