SURFACE ELECTROMIGRATION AND SELF-DIFFUSION ON GOLD-FILMS STUDIED VIASCANNING-TUNNELING-MICROSCOPY

The evolution of monolayer islands, voids and terraces on the surface of polycrystalline gold films due to atomic self-diffusion and upon cu rrent stressing (electromigration) is studied using scanning tunneling microscopy. At room temperature with no current stressing isolated is lands and voids shrink, while in regions having high step density the area of terraces remain nearly constant, suggesting that surface dynam ics is dominated by atom diffusion along the terraces. In contrast, wh en current is driven through the film, we occasionally find enlargemen t of voids and islands. In addition, we observe migration of steps lea ding to variations of terrace areas and, in some cases, to step bunchi ng, indicating a significant contribution from atoms hopping over step s. Our data on the evolution of monolayer islands and atomic steps als o provide information on activation energies for detachment from steps .