Scanning tunneling microscopy observation of hydrogen-induced Ag cluster formation on the Si(111) surfaces

Using a scanning tunneling microscopy (STM) we have studied the nucleation and growth process of Ag clusters induced by the atomic hydrogen adsorption on the Si(111) √3×√3(R30°)‐Ag (simply √3‐Ag) surface. Size distributions of the clusters have been investigated as a function of the exposure of atomic hydrogen, and it is strongly suggested that the surface migration of Ag atoms over the hydrogen‐reacted regions is largely suppressed compared with that on the √3‐Ag surface. The size of Ag clusters is less than 150 A and their average height is estimated to be 3.1 atomic layers, consistent with previous ion scattering results. We have proposed the model of nucleation and growth process of hydrogen‐induced Ag clustering in which the broadened H/√3‐Ag regions suppress the migration of expelled Ag atoms and lead to the formation of many small clusters.