MOLECULAR-DYNAMICS STUDIES OF CLUSTER EMISSION IN SPUTTERING

The emission of neutral clusters can constitute a sizeable fraction of the total sputtered flux under energetic (keV) ion bombardment of metal surfaces. We have performed Molecular Dynamics (MD) simulations of the sputtering process for Ar on Cu(111) and ion energies up to 5 keV. Using a many-body interaction potential we have analysed in detail the processes leading to cluster emission, in order to gain a microscopic understanding of these phenomena. Results obtained for cluster emission will be presented and compared with single atom emission. Their yields and energy distributions (up to pentomers) will also be compared with recent experimental results using (non)resonant laser multiphoton post-ionisation in combination with the Time of Flight technique. From the results of the MD calculations we propose a new model for the emission of large clusters, which is still a puzzling phenomenon in sputtering.