Diffusion-induced step decoration of Co on Ag(001)

We have investigated submonolayers of Co deposited on a Ag(001) surface wit h ultra low energy ion deposition and a deposition energy ranging from 5 to 30 eV. The sites of nucleation, the island densities and heights were dete rmined with scanning tunneling microscopy. Next to randomly distributed isl ands on the terraces observed for every deposition energy, preferential nuc leation on the upper side of the Ag steps was observed only for 5 and 15 eV . We found that for increasing characteristic length between the islands on a terrace, the number of islands per unit step length increases. This impl ies that step decoration is related to enhanced diffusion of Co atoms on th e Ag surface during nucleation. (C) 2000 Elsevier Science B.V. All rights r eserved.