On the energy efficiency of sputtering

The optimum energy and the type of sputtering inert gas (Ne, Ar, Kr or Xe) used to achieve maximum productivity of the sputtering process of elemental targets, are assessed using the sputtering yield formula of Yamamura. The erosion efficiency η was found to have maximum at ion energy E of 7Eth (Eth is the threshold energy for sputtering). ηmax exhibits oscillations with the atomic number Z2 of the target and has values in the interval 0.4-4%. This efficiency is relatively high (η > 0.8 ηmax) for E between 3Eth and 20Eth which for most ion-target combinations corresponds to energies within the 50-1000 eV interval. The ηmax values for a given target do not differ significantly for different inert gases. For Z2 < 50 targets Ar provides sufficiently higher efficiency (within 20% compared with other inert gases) while for heavier targets Kr and Xe can have 40-70% higher efficiency than Ar. 3 figs, 17 refs