Secondary ion emission from transition metals during exposure to oxygen and subsequent sputtering

Abstract

The interaction of oxygen with three transition metals (Ti, Ni, and Nb) was studied by means of high fluence secondary ion mass spectrometry. It was established that at high oxygen coverages secondary ion intensities during O2 exposure and subsequent sputter removal exhibited an almost identical evolution, indicating that secondary ions are emitted from similar structures in both stages. During sputter removal all measured ion signals I followed approximately an exponential dependence on the primary ion fluence φ, with I α exp (-σ, φ). This behaviour can be attributed to the collisional relocation of oxygen atoms in the metal substrate. The parameter Ym/σi (where Ym is the sputtering yield of the metal) characterizes the extent of ion beam-induced mixing for a given oxygen-metal system. For the same element, Ym/σi was found to depend slightly on the ion species monitored. Mean values (in atoms/cm2) were 5.2 × 1016 for Ni, 7.4 × 1016 for Nb, and 1.4 × 1017 for Ti.