Energy distributions of metal atoms and monoxide molecules sputtered from oxidized Ta and Nb

Abstract

The energy distributions of Me atoms and MeO molecules (Me=metal) sputtered by 2 keV Ar + ions have been determined by means of energy resolved secondary neutral mass spectrometry (SNMS). The oxygen surface concentration c O s of the polycrystalline samples was varied by oxygen exposure under simultaneous Ar + bombardment. In particular the normalized Me energy distributions became significantly broader with increasing c O s , while such an influence was less pronounced for MeO. Additionally, the c O s -dependence of the partial sputter yields Y Me and Y MeO was obtained by integrating the respective energy spectra. While Y Me is found to decrease monotonously with increasing c O s , Y MeO shows a maximum around c O s =0.5, which in the case of Ta has been reported earlier. This nonmonotonous behaviour as well as the observed c O s -dependence of the Me and MeO energy distributions is discussed in terms of an energy dependent version of the direct emission model proposed earlier for the formation of sputtered MeO.