Au-Si bonding on Si(111) surfaces

To investigate the Au-Si bonding feature on Si(111) surfaces, surface energy calculations have been performed for 1 x 1- and root3 x root3-Au/Si(111) systems by the first-principles method in a local density approximation. It Was found that the Au overlayer considerably stabilizes the Si(111) surface. By analyzing the changes in the surface energy and the charge density at various Au positions on the surface, it was shown that the large electronegativity of Au produces covalent-like Au-Si bonds by either terminating dangling bonds of surface Si or inducing the charge transfer from Si-Si to Au-Si bonds, both of which promote surface stabilization and determine the Au overlayer height on Si(111) surfaces.