Some effects of ion mass on the energy spectrum of sputtered gold atoms

Abstract
Energy spectra of gold atoms sputtered from polycrystalline gold targets by D+, He+, Ar+, Kr+ and Xe+ in the range 10 to 20 keV are reported. On successively increasing the ion mass from Ar+, the low-energy peak of the spectrum shifts from E ∼ E b/2 for Ar+-Au to ∼ Eb/20 for Xe+-Au, where Eb is the surface binding energy. The effect of decreasing the ion mass from Ar+ to He+ and D+ is to enhance relatively the sputtering at higher energies in the spectrum between 200 and 500 eV. Theories based on extended collision cascades predict a peak at Eb/2 and an E−2 tail for E≫Eb . The observed departures from this behaviour are attributed to non-linear spike effects in the cases of very heavy ions, and to recoils from the reflected flux in the cases of light ions.