Synergistic sputtering effects during ion bombardment with two ion species

Abstract

The modification of the sputtering yield during ion bombardment with two ion species of different masses is studied with the dynamic Monte Carlo code T−DYN. Specifically, the sputtering yield of low mass targets with low to medium mass primary ions is substantially enhanced when a second ion species of higher mass is introduced. This enhancement is due to the incorporation of the heavier ion species into the target material thus changing significantly the collision cascade behavior of the primary ions. As a result, the energy deposited at the surface is increased and hence the sputtering yield is also increased. This sputter yield enhancement is found to be a function of the ion energy, angle of incidence, masses and atomic densities of the two ion species, steady state concentration of the secondary ion species at the surface (primary to secondary ion ratio), etc. The effect is found to be most pronounced at low energies where the sputter yield enhancement is predicted to increase by a factor of 2 or more. The mechanisms of the sputter yield enhancement as well as the modification of the energy deposition function are discussed in detail.