Very large gold and silver sputtering yields induced by keV to MeV energy Aun clusters (n=1-13) -: art. no. 144106

The total sputtering yields of gold and silver targets bombarded by Au-n (n=1-13) clusters have been measured over a broad range of incident energy per atom (from 20 keV/atom to 5 MeV/atom). Large nonlinear effects in the sputtering yields were observed. For silver targets, yield values as high as similar to20 000 atoms per impact of Au-13 at 1.2 MeV (92 keV/atom) were measured while only 45 atoms are emitted from the same target in the impact of single gold atoms at the same energy per atom. The sputtering yield variation with incident projectile energy per atom shows that maxima occur at similar to250 keV/atom for a gold target and similar to150 keV/atom for a silver target for projectiles with three or more atoms. In both cases the maxima of nuclear stopping power are at much larger energies per atom (700 keV for Au on Au and 550 keV for Au on Ag). Large surface deformations with craters and rims are observed by atomic force microscopy at the surface of cluster irradiated targets. Their number per unit area corresponds to the irradiation fluence and they are of approximately the same size, demonstrating that fluctuations between events are small.