Implantation depth of size-selected metal clusters into graphite

We have investigated the implantation of size-selected Ag-7(-) clusters into the graphite surface as a function of kinetic energy (E) from 1.0 to 5.5 keV, via scanning tunnelling microscopy together with molecular dynamics simulations. By utilizing thermal oxidation of the graphite surface to expand laterally the defects created via implantation, we find that the cluster implantation depth is proportional to rootE and hence the velocity of the bombarding cluster. By careful control of the oxidation temperature, we also demonstrate that even moderate temperatures (923-1123 K), considerably lower than the melting point of graphite (4450 K), lead to significant annealing of the defects formed through cluster impact, accounting for the shape of the experimental depth distributions observed.