Sputter-induced compositional modifications in a Ni-Au alloy

Surface and subsurface composition changes induced by heating and by ion sputtering of a Ni-6 at% Au alloy at temperatures between 25 and 6000C were measured in situ, using the ion-scattering-spectroscopy technique. Upon heating, Au atoms segregated to the alloy surface; the enthalpy and entropy of Gibbsian adsorption were found to be -0.45 eV and -1.09k. During sputtering, the steady-state surface composition was noticeable temperature-dependent above proportional4000C, which could be interpreted in terms of significant contributions of the second atom layer to the sputtered-atom flux. Steady-state concentration profiles measured after rapid cooling of the target to room temperature were analyzed to gain information about the temperature dependence of the effective altered-layer thickness, from which radiation-enhanced diffusion coefficients in the bombarded alloy were determined. (orig.)