SCANNING-TUNNELING-MICROSCOPY INVESTIGATION OF THE NUCLEATION AND GROWTH OF AG SI(111)-(ROOT-3X-ROOT-3)/

The scanning tunneling microscope has been used to identify and distin guish between various stages of reactive growth of Ag on Si(111)-(7 X 7) at 450-degrees-C. Continuous investigation of the reaction trend wa s made possible by producing a concentration gradient of Ag on the sub strate. The surface features observed, such as hole-island pairs, are dependent on the sample coverage. Mechanisms for the formation of Ag/S i(111)-(square-root 3 X square-root 3) are proposed, and experimental confirmation of their validity is presented. Antiphase boundaries betw een neighboring (square-root 3 X square-root 3) domains have been obse rved, and a model for the atomic structure across such a boundary is s hown. At near monolayer coverages small regions that exhibit the Si(11 1)-(1 X 1) structure have been identified.