Comparative study of kinetic energy spectra and mass distributions of Ta n+ ions sputtered from tantalum by atomic and molecular ion bombardment

Abstract

Mass distributions and kinetic energy spectra of Ta n + ions ( n ≤ 12) sputtered from a tantalum target by Au m − primary ions ( m = 1,2,3), with energies of 6 keV per constituent atom, have been determined under identical experimental conditions. Under the molecular ion bombardment, anomalous high non-additive sputtering yields were observed for large metal clusters. For instance, a relative yield of Ta 10 + clusters under Au 3 − molecular ion bombardment was observed approximately 2000 times higher than that under Au − atomic ion bombardment. The comparison between mass distributions and kinetic energy spectra determined under the molecular ion bombardment and those for the atomic ion bombardment showed both qualitative and quantitative differences. A hypothesis about the existence of different cluster ion emission mechanisms for small clusters of several atoms and for larger ones is proposed.