Bonding and diffusion of Ba on a Si(001) reconstructed surface

Abstract

Bonding and diffusion of a Ba adatom on a Si(001) surface have been studied using first-principles density-functional calculations. It is found that the favorable bonding site of the adatom is the fourfold site located in the trough between Si dimer rows. The bonding between Ba adatom and the surface is shown to be only slightly ionic in character, with a small charge transfer from Ba to the substrate, and with an important covalent component. The calculated jumping rates show a strongly anisotropic diffusivity of Ba on the surface.