Near-threshold sputter yields of ruthenium under argon and nitrogen ion bombardment

Abstract

Ion surface interactions near sputter-threshold are of interest for various plasma facing materials. We report experimental determination of sputter yields for ruthenium films grown on a quartz crystal microbalance and exposed to Ar+ and N2+ ions in the energy range of 50–300 eV. Comparison to semi-empirical models shows agreement to previously reported yields for argon bombardment. In the case of nitrogen, the Yamamura model was modified to account for molecular effects and the yields are found to be between extremes of rigid and non-rigid molecular approximations proposed by Yao. Ex-situ XPS measurements revealed implantation of nitrogen in the ruthenium film after exposure to nitrogen ions. The discrepancy between the models and experimental results for N2+ bombardment is explained by an increase in the surface binding energy of the target leading to a chemically reduced sputter yield.