Influence of the bombarding angle on the sputtering yield of heavy atomic and molecular ion bombardment of Ag and Auf

The sputtering of polycrystalline Ag and Au by heavy atomic and molecular ion bombardment has been measured as a function of the ion beam angle of incidence, θ Comparison is carried out between the measured and calculated values where the calculated values are based upon determination of the surface deposited energy assuming infinite (transport theory) and semi-infinite (Monte-Carlo calculation) media. It is found that the angular dependence, out to 75° from normal incidence, of the measured sputtering yield for Ag and Au bombarded with heavy atomic and molecular ions of Sb and Bi are somewhat different, with the Ag sputtering yields showing a slower rate of increase with θ at large (θ ≳ 70°), than in the case of Au sputtering. Also the sputtering by molecular ions shows a much larger sputtering yield/atom than for the same velocity monatomic bombardment. This enhancement increases non-linearly with the number of atoms/molecule, but decreases with the angle of incidence. It is found that the sputtering yield as a function of angle of incidence becomes increasingly lower than would apparently result for a normal incidence bombardment having the equivalent value of surface deposited energy. This is consistent with increasing ion reflection at larger angles of incidence reducing the molecular ion enhancement factor and a further reduction associated with expected smaller depth topographical features as the angle of incidence increases.