Self-sputtering of silver by mono- and polyatomic projectiles: A moleculardynamics investigation

The self-sputtering of silver under bombardment with Ag-m (m=1,2,3) project iles has been investigated by molecular dynamics (MD) simulation using the many body MD/MC-Corrected Effective Medium Potential developed by DePristo and co-workers. More specifically, the total sputtering yield as well as th e mass distribution, i.e., the distribution of monomers and clusters within the flux of sputtered particles were calculated. For di- and triatomic pro jectiles, we observe a pronounced dependence of the calculated yields on th e orientation of the incoming cluster, whereas the internuclear distance (a nd thus vibrational excitation of the projectile) does not seem to play a s ignificant role. When averaged over the impact orientation, the calculated yields per projectile atom exhibit a distinct nonlinear enhancement when co mpared to the respective values calculated for monatomic projectiles of the same impact velocity. The abundances of nascent and final Ag-n clusters (i dentified immediately above and far away from the surface, respectively) wi thin the sputtered flux are found to be significantly enhanced under polyat omic projectile bombardment, the effect increasing with increasing size of the sputtered cluster. Moreover, clusters produced under polyatomic bombard ment appear to be colder, a finding which might be of considerable interest in the light of mass spectrometric surface analysis techniques. (C) 2001 A merican Institute of Physics.