NEAR-SURFACE COMPOSITION MODIFICATIONS IN AG-AU-CU ALLOYS BY ION SPUTTERING AT ELEVATED-TEMPERATURES

Surface and subsurface compositional changes in a Ag40at%Au20at%Cu alloy at temperatures between 30 and 600°C were investigated using ion scattering spectroscopy. Upon heating the alloy, Cu and Au atoms segregated away from the surface. The entropies and enthalpies of Gibbsian segregation were determined to be 0.69k and 0.134 eV for Cu, and - 0.21k and 0.06 eV for Au, respectively, in the temperature range of 400-700°C. The time evolution of the surface compositions during 3 keV Ne+ sputtering and corresponding steady-state compositional profiles were measured as a function of temperature. By comparing model calculations of near-surface compositional changes in the alloy with the experimental observations, useful information about the depth of origin of sputtered atoms and the defect properties in Ag-Au-Cu alloys was derived. The sputter fraction from the second atom layer was γ = 0.1; the effective vacancy formation energy was 1.12 eV; and the energies of vacancy and interstitial migration via Ag, Au and Cu were 0.66, 0.84 and 0.75 eV, and 0.06, 0.15 and 0.14 eV, respectively. © 1990.