Early Stages of Submonolayer Growth of Ag on Si(111) 7×7 Observed by Scanning Tunneling Microscopy In Vivo

Scanning tunneling microscopy (STM) was used for directly imaging the early stages of heteroepitaxial growth of Ag on a Si(111) 7×7 surface during deposition by vacuum evaporation. Image sequences showed the behavior of single Ag adatoms after arriving on the surface and the formation of Ag clusters. STM measurements were performed at room temperature and 330 K. New data showed an attractive interaction between a cluster containing at least two Ag atoms and a monomer occupying an adjacent half-unit cell of surface reconstruction. The interaction modified the Ag adatom mobility on the surface and controled the growth scenario from the moment when the relative number of occupied half-unit cells is ≈0.5. The observation of the individual Ag adatom history on the surface enabled the interpretation of STM imaging of the smallest Ag objects, i.e., monomers, dimers, and trimers. The previously reported models of metal growth on the Si(111) 7×7 surface derived from in situ STM measurements are discussed with respect to the new data.