ATOM INCORPORATION AT SURFACE CLUSTERS - AN ATOMIC VIEW

Observations have been made of the incorporation of single iridium atoms into ascending as well as descending steps at iridium clusters on Ir(111). At ascending steps, incorporation occurs once diffusion of adatoms becomes significant. At descending steps, it is more complicated, and proceeds differently on large compared to small (12-atom) clusters. The mechanism of incorporation has been tested in experiments with tungsten atoms. These reveal that incorporation at descending steps can occur by exchange of the adatom with a cluster atom rather than by simple jumps.