KINETIC PROCESSES IN METAL EPITAXY STUDIED WITH VARIABLE-TEMPERATURE STM - AG PT(111)/

Variable-temperature scanning tunneling microscopy has been applied to study kinetic processes involved in epitaxial growth. This paper conc entrates on nucleation and aggregation of submonolayer Ag films on a P t(lll) surface. From island density versus temperature data, the activ ation barrier for Ag adatom diffusion as well as the stability of adso rbed Ag dimers are determined. From the adsorbed aggregate shapes conc lusions on Ag perimeter diffusion can be drawn. An anisotropy in edge diffusion leads to dendritic aggregates with the trigonal substrate sy mmetry. A crossover to randomly ramified fractals is observed upon low ering of the deposition flux.