Sputtering of clusters from copper–gold alloys

Abstract Polycrystalline Cu, Cu 20 Au 80 , Cu 40 Au 60 , Cu 80 Au 20 and Au samples were bombarded with 15 keV Ar + , and the resulting secondary neutral yield distribution was studied by non-resonant laser post-ionisation mass spectrometry. Neutral clusters containing up to 15 atoms were observed for the targets. The yield of neutral clusters, Cu m Au n − m , containing n atoms, Y n , was found to follow a power in n , i.e. Y n ∝ n - δ , where the exponent δ varied from 5.2 to 10.1. For a fixed n , the cluster yields showed a variation with number of copper atoms, m , much greater than expected for a binomial distribution suggesting that the clusters are not formed randomly above the surface and a component of preformed cluster emission occurs. In addition, the cluster compositions from the sputtered alloys were indicative of sputtering from a copper rich surface.