Sputtering of frozen Xenon by keV heavy ions

Sputtering measurements of frozen Xe have been made using 20–80 keV heavy ions (N, Ar, Sb and Bi), i.e. where nuclear stopping is the dominant energy loss process. Sputtering yields (Y) of up to 1.6 × 104 Xe atomsion have been obtained. The dependence of Y on the surface deposited (nuclear) energy FD(0) was found to exhibit two distinct regimes: at low FD(0) values, Yincreases linearly with deposited energy, as predicted by cascade sputtering theory, but above a threshold value of ≈500 eVÅ2/atom the sputtering yield exhibits a much stronger (approximately cubic) dependence on FD(0). Comparison of the sputtering yields obtained by monatomic and diatomic equal velocity heavy ion bombardments (e.g. Sb/Sb2) further confirmed this non-linear behaviour at large FD(0). Similar monatomic and diatomic light ion bombardments (e.g. N/N2) showed no molecular enhancement, hence a linear behaviour at lower FD(0). The current results, which are obtained in the energy regime where nuclear stopping dominates, are compared to earlier measurements at MeV energies in which electronic stopping dominates. This comparison suggests that the observed sputtering behaviour of frozen Xe is complex, with significant contributions from both nuclear and electronic processes.