Elevated-temperature sputtering of Ni--Au alloys: Surface and subsurface composition modifications measured by ion scattering spectroscopy

The effects of 3-keV Ne+ ion sputtering on surface and subsurface compositions of a Ni--6 at. % Au alloy at temperatures between 25 and 6000C were investigated using ion scattering spectroscopy. The equilibrium composition in the surface atom layer during heating prior to sputtering, the time evolution of the surface composition during sputtering, and subsurface concentration profiles after rapid specimen quenching to room temperature were measured as a function of temperature. The steady-state composition at the alloy surface was found to be temperature dependent during sputtering at temperatures above approx. 4000C, which was attributed to significant contributions of the second atom layer to the sputtered-atom flux. This interpretation was supported by the results of theoretical modeling which was performed using the kinetic model of Lam and Wiedersich. From the steady-state concentration profiles measured, the effective altered-layer thicknesses were determined, and information about radiation-enhanced diffusion in the bombarded alloy was also obtained