The sputtering of insulating materials by fast heavy ions

In this paper we review recent experimental results from our laboratory on sputtering of UF_4 and H_2O (ice) by fast heavy ions. Measurements have been made of the dependence of the sputtering yield on the incident ion type, charge state and energy. In the case of UF_4 the energy spectra of neutral sputtered particles have been obtained as well. There is a clear dependence of the sputtering yield on the electronic part of the stopping power, and the yield is strongly affected by the charge state of the incident ion, which shows that in the near-surface region from which sputtered particles arise the charge state of the incident ion has not reached equilibrium. The shape of the energy spectra observed for UF_4 targets is that expected from a thermal distribution rather than that of the collision cascade from typical of ordinary sputtering. A model of the sputtering-track registration process that has arisen from these data is shown to provide a framework for understanding the close relationship of our observations to the "plasma desorption" of macromolecules.