Angular distributions of sputtered particles ejected from pure Cu, Pt and Cu-Pt alloy under 3 keV Ar+ ion bombardment

The 'over-cosine' distribution peculiar to the angular distribution of Pt atoms sputtered from pure Pt and Cu-Pt (19 at.%) alloy targets has been studied experimentally and theoretically. The angular distributions were measured for pure Cu, Pt and Cu-Pt alloy under 3 keV Ar+ ion bombardment at different incident angles in ultrahigh vacuum. Significant 'over-cosine' distributions of sputtered Pt atoms have been observed for both the pure Pt and Cu-Pt alloy, as reported by Andersen et al. As a theoretical approach, Monte Carlo simulation has been performed by taking into account the altered layer formed on the alloy surface, which was obtained experimentally in the previous study. The comparison between the experiment and the simulation has revealed that the peculiarity of the angular distribution of sputtered Pt atoms still cannot be understood by the present simulation, whilst the simulation describes the angular distributions of other metals with considerable success. (author)