Au adsorption on stepped Si(hhk)-Au surfaces

Abstract

The impact of submonolayer gold adsorption on metallic atomic wires grown on terraced silicon substrates is modeled from first principles. Calculations within density functional theory predict Au adsorption at the Si step edge of the Si(553)-Au surface and moderate mobility of the Au adatoms. Although the Au adsorption at the Si step edge does not substantially modify its geometry, a large adsorbate-to-substrate electronic transfer is predicted, which causes a rearrangement of the electronic band structure. The electronic states related to the Si step edge are shifted below the Fermi energy, while an electronic gap opens between the Au-related electronic states. The gap opening leads to a strong enhancement of the Au-chain dimerization. The Au adsorption at the step edge thus modifies the surface morphology non-locally, as a consequence of the strong electronic correlation in quasi-1D systems. Au adsorption on the Si(775)-Au nanowire system occurs mainly at the Au chain, and then at the Si step edge, instead. Adsorption at the Au chain directly modifies its structure by the formation of a structural defect, while adsorption at the step edge has the same effect as in the case of the Si(553)-Au system.