Composition of sputtered material from CuNi alloy during Xe⁺ ion sputtering at elevated temperatures

Polycrystalline CuNi alloys were sputtered by 3 kV Xe⁺ ions at elevated temperatures to analyze the ion-beam-induced diffusion. The time evolution of the composition of the sputtered materials from the start of the sputtering was measured by TOF-SNMS (time-of-flight sputtered neutral mass spectrometry). During removal of the Gibbsian segregation layer of copper, the sputtered flux consisted of almost only copper atoms. Then, the copper content gradually decreased due to the formation of a sputter-induced copper-depleted surface layer, and reached an almost steady state with still higher copper content than the bulk composition. From the temperature dependence of the composition at the quasi-steady state the activation energy of copper transportation through a high diffusivity path was derived to be 54 kJ mol^-1 (0.56 eV). The high diffusivity path was assigned to copper diffusion through grain boundaries.