Au Adsorption on Regular and Defected Thin MgO(100) Films Supported by Mo

Abstract

Using density functional theory we studied systematically a Au atom adsorption on a Mo-supported regular and defected ultrathin MgO film with 1 to 5 ML thickness. On Mo(100) grown regular MgO Au prefers to adsorb at a hollow site instead of an O site found for single-crystal MgO. The metal support also enhances Au adsorption energy in agreement with the earlier theoretical results. Adsorption energy decreases with increasing film thickness being, however, even in the case of 5 ML thick MgO much higher than that on single-crystal MgO. The Bader analysis was performed to estimate the spatial distribution of charge in different cases. The results show charge transfer (0.7−0.8 e) to the Au atom, fairly independent of the oxide thickness, and density difference plots display a rich polarization pattern on the oxide upon Au adsorption. The Au atom bound to an oxygen vacancy forms a chemical bond with the defect. In this case, the Au adatom is charged by about 1.2 e, and the charge transfer depends on neither the MgO film thickness nor the presence of the Mo support.