A comparison of secondary ion and photon yields from ion bombarded CuNi alloys

Abstract

The secondary ion and photon yields produced by 7 keV Ar + ion bombardment of a series of polycrystalline CuNi alloys under ultrahigh vacuum conditions have been compared. By measuring the relative alloy sputtering rates and the ion and photon yields at steady state conditions, the matrix effects on both relative ionization and excitation probabilities have been investigated. The Ni excitation and ionization efficiencies decrease when Cu is alloyed with Ni. On the other hand, the addition of Ni to Cu initially depresses the Cu ionization and excitation efficiencies. These efficiencies are subsequently enhanced as the Ni content of the alloy is increased. The ratio of both ion and photon emission probabilities of Cu compared to Ni remains independent of alloy composition, i.e. yields are similarly enhanced from the same surface. The initial decrease in yields from the low Ni content alloys makes predictions about the nature of the enhancement mechanism difficult. These results do not favour any simple surface electronic structure model.