Electronic structures of 3×3-Au/Si(1 1 1) surface

Band structure of the (3×3)R30°-Au/Si(1 1 1) surface is calculated by the ab initio pseudopotential method in a local density approximation. It is shown that the surface is semi-metallic; two bulk-Si valence bands and one Au–Si hybridized conduction band overlap slightly at the center of the Brillouine zone. We found three facts: Au trimers are located higher than the Si topmost layers, the charge redistribution occurs from d to s orbitals around Au due to strong electronic-state hybridization between Au and Si, and the formation of Au–Si bonds induces the charge transfer from Si to Au–Si bonds. All the facts cause the observed increases by Au adsorption of both the work function and the core-level binding energies of Au and Si.