Ion bombardment effects on the near‐surface composition during sputter profiling

Abstract The alteration of the near‐surface composition that has often been observed in ion bombarded alloys and compounds results from the dynamic interplay of several processes. In addition to displacement mixing leading to a randomization of atomic locations, which is dominant at relatively low temperatures, and preferential loss of alloying elements by sputtering, many thermally‐activated processes, including radiation‐enhanced diffusion, radiation‐induced segregation and Gibbsian adsorption, also play important roles. The relative significance of each process in the evolution of the sputtered flux composition and of the compositional profile of the target depends on the type of alloys, temperature and ion characteristics. Although a good semi‐quantitative understanding already exists for most of the individual processes, the number of systematic investigations of alloy sputtering that consider all of these processes and their potential interactions is still rather limited. A fundamental understanding of the synergistic effects of these processes is, however, essential for quantitative analysis of multicomponent‐material surfaces, since sputtering is routinely applied in conjunction with various analytical techniques to depth‐profile the composition. The purpose of this paper is to characterize the processes in simple physical terms and to point out under what conditions they may become important for compositional changes in near‐surface regions of sputtered alloys, based on selected results of recent model calculations and experimental studies.