Simulation of isotopic mass effects in sputtering, II

Abstract

We have reinvestigated isotope effects in sputtering from the Ar^+−Cu and the Ar^+-pseudo-Cu systems using the multiple-interaction (MI) simulation technique with a target generator that maintains a fixed ratio of light to heavy atoms. A new target configuration was generated prior to the simulation of each impact. The changes in target generation technique were made in response to a suggestion by Sigmund that the results of a previous simulation study of this problem may have included large systematic errors. In this study targets with equal numbers of light and heavy atoms were generated. Mass differences ranged from 3% to 20%. The sputtered material generally was found to be enriched in the light isotope. This enrichment was greatest for material ejected near the normal to the target surface. Our present results are in good agreement with our previous simulations and with the experimental results of Gnaser et al.

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