Abstract
Using variable-temperature scanning tunnelling microscopy (20—700K) we analysed single Ne+, Ar+, Kr+ and Xe+ (4.5 eV) impacts on Pt(111). The adatom yield, the number distribution of adatoms created per impact, the radial distribution of the adatoms and the mean sizes of produced adatom and vacancy clusters were determined. Ne+ (4.5keV) impacts produce only isolated adatoms with a number distribution of adatoms per impact close to the Poisson distribution. The adatom yield is compatible with a linear cascade model. At an increased energy density corresponding to an Ar+ (4.5keV) impact, the adatom production mechanism changes. At this and higher energy densities, adatom clusters with number distributions much broader than the corresponding Poisson distribution are created. This and an increased ratio of adatom yield to sputter yield indicate that collective effects have to be taken into account to describe adatom production. Molecular dynamics simulations performed for Ne and Xe (4.5 keV) impacts on Pt(111) and presented in the accompanying paper reproduce the experimental trends and conclusions. Experiments with successively increasing fluence give evidence that an ion induced adatom mobility occurs at lower energy densities (Ne+ (4.5 keV) impacts). In addition, for Xe bombardment at higher energies (6.5 keV), vacancy cluster formation below the surface is found.
