Cluster size dependences of bombardment effects using mass-selected gas cluster ion beams

Bombardment effects induced by mass-selected gas cluster ion beams (GCIB) were studied. In this study, a mass-selected GCIB system using a strong permanent magnet was employed and the cluster size effects of sputtering by GCIB irradiation were studied. The cluster size varied between 500 and 10,000 atoms/cluster. The sputtering yields of Au with mass-selected Ar-GCIB decreased with an increase in the cluster size because of a decrease in the energy per atom. The threshold energy for the sputtering of An by Ar-GCIB was approximately 0.6 eV/atom, which was significantly lower than that by Ar monomer ions (20 eV). Although the energy per atom of the cluster ions was low, dense energy deposition occurred near the surface and surface An atoms were effectively ejected. When the number of Ar atoms transferred by the clusters and the energy per atom were equivalent, the number of sputtered Au atoms was also same. (c) 2007 Published by Elsevier B.V.