Scanning-tunneling-microscopy study of initial stages of Au adsorption on vicinal Si(111) surfaces

The initial stages of Au deposition (0.3 ML) on a vicinal Si(111) surface misoriented by 4 degrees toward the [11 (2) over bar] direction have been studied using scanning tunneling microscopy (STM). We have found that the Au adsorption transformed bunched steps into well-ordered Au-adsorbed (111) terraces, while the 7 X 7 structures were still present. A 5 X 2 unit cell was a good match for the Au-adsorbed terraces. At the domain boundaries of the 7 X 7 and Au-adsorbed structures, only one unit of the 5 X 2 structure grew from the step edge of the 7 X 7 terrace. This boundary structure played an important role in forming the well-ordered Au-adsorbed terraces. Each step edge of the Au-adsorbed terrace was reconstructed into a two-unit cell. A model of the Au adsorption and step-edge reconstruction based on STM observation was proposed.