Investigation of the formation of M-2(+)-molecular ions in sputtering processes

Abstract

The formation process of M-2(+) molecular ions sputtered from elementary target materials is investigated. in a previous article it was shown that these molecules can be used to quantitate major elements [1]. The quantitation method was based on the assumption that the M-2(+) molecular ions are formed by the atomic combination of independently sputtered M and M+ particles above the surface. In this paper this assumption will be investigated using a Monte Carlo model to simulate the formation mechanism. The model is used to calculate the velocity distribution of the M: dimers sputtered from three different elementary target materials (Fe, Ge, and Ni). The results are compared with experimental data. Good agreement exists between theory and experiment that supports the Monte Carlo model and hence also the assumed formation mechanism. (C) 1999 American Society for Mass Spectrometry.