Surface concentration modification of PtPd alloys by noble gas ion sputtering

Abstract

AbstractThe surface concentration of three PtxPd1 − x alloys (x = 0.3, 0.5 and 0.7) under ion bombardment was studied as a function of ion species and ion bombardment energy for the noble gas ions He, Ne, Ar and Xe in the 0.5–1.25 keV energy range. The surface composition was measured by low‐energy ion scattering spectroscopy (ISS) and Auger electron spectroscopy (AES). It was observed that Pd is preferentially sputtered from the surface of these alloys (as corroborated by previous studies). This effect was found to be greatest for the lightest ion (He) and most pronounced for the lowest energies used. Only a very weak dependence of the surface concentration on the energy of the heaviest ion (Xe) was detected. Comparing ISS and AES (true surface and near‐surface information respectively), it was also found that Pd is depleted in the near‐surface region. The depletion is ascribed to radiation‐enhanced diffusion and segregation and it is shown how the overlaid contour mapping of ISS and AES intensities, as a function of diffusion coefficient D and segregation energy ΔG, may be used to determine the radiation‐induced diffusion coefficient D as a function of ion species and ion energy.