Sputtering of high-energy metal ions in keV heavy-ion surface collisions

Spectra of high-energy negative and positive metal ions sputtered from Cu(110) and Al(111) by keV noble-gas ions and measured at large recoil angles are presented. We have identified the most important mechanisms that lead to sputtering at these high energies. A comparison with a model based on MARLOWE simulations and on the electron tunneling model shows that for Cu(110) a significant fraction of the high-energy sputtered particles leaves the surface in a positive charge state. At the surface, the fraction of sputtered negative ions is two orders of magnitude smaller. On the outgoing trajectory most of the ions are neutralized by resonance neutralization. The rate for neutralization of the positive ions has been found to be significantly higher than for the negative ions.