Hydrogen-Induced Ag Cluster Formation on the Si(111) √ 3×√ 3(R30°)-Ag Surface Observed by Scanning Tunneling Microscopy

Abstract
The scanning tunneling microscope (STM) has been used to study structural transformation of the Si(111) √ 3×√ 3(R30°)–Ag surface caused by atomic hydrogen adsorption. When atomic hydrogen adsorbs on the √ 3-Ag surface, the Ag atoms are expelled to form clusters. The size of the Ag clusters has been confirmed to be less than 150 Å in agreement with previous ion scattering results. Spatial distributions of the clusters, observed as functions of the exposure to atomic hydrogen, reveal that surface diffusion of Ag atoms over the hydrogen-covered regions is largely suppressed compared with that on the √ 3-Ag surface. The clusters are hexagonal and their orientations suggest the formation of Ag(111) clusters.