Theoretical study of Sn adsorbed on the Au(1 1 1) surface

Abstract

In the present work, the adsorption of Sn atoms on the Au(1 1 1) surface was theoretically studied in the framework of density functional theory with a slab model. The results show that the most likely site for the adsorption of Sn is the FCC hollow site at low Sn coverage while at full monolayer degeneracy is produced for the four possible adsorption sites. The energy barrier for Sn surface diffusion is of near 0.1 eV at low coverage and negligible at high coverage. The magnitude of the Sn adsorption energy, Eads, decreases as the overlayer grows. For high coverage values the Sn-Sn interaction has a predominant contribution to Eads. It was observed that for 1/2 ML coverage the adsorbed Sn atoms and the Au atoms of the first and second layers of the substrate can suffer a reordering, resulting in an important surface reconstruction, giving a surface alloy superstructure. An electronic transfer from tin to gold takes place, which is significant at low Sn coverage. The binding of Sn to Au was analyzed in terms of the electronic structure of the Sn/Au(1 1 1) system at different values of coverage.