Ion-beam-induced isotope composition changes in metal surfaces and recoil implantation

Abstract

It was found that the isotope ratios of ⁵⁸Ni/⁶⁰Ni and ⁶³Cu/⁶⁵Cu measured by SIMS changed by a few percent at the initial stage of ion bombardment for well-polished pure metal samples. A similar change was also found for silver, palladium, titanium and chromium targets. The isotope ratios, the light to the heavy, for the fresh surfaces were low at first and increased with time to reach constant values as the ion bombardment continued. It was pointed out that the main process able to induce such a large mass effect would be preferential recoil implantation of isotopes by primary ions.