Changes in alloy surface composition induced by low energy ion bombardment

The surface composition of alloys and compounds can be altered by ion bombardment. With respect to Kelly's analytical model, a basic analytical relationship is given in this paper by considering preferential sputtering (PS), ion radiation induced segregation (RIS), and radiation enhanced diffusion (RED) effects. The PS correction factor, RIS correction factor, and RED correction factor are included in the relationship. The surface composition and composition depth profiles of alloys Au-Cu, Cu-Ni, and Au-Pd have been investigated by our model. It is found that they are in agreement with the experimental results reported in the literature. We think that the RED diffusion coefficient may play an important role besides surface segregation. It is estimated that the RED activation energy is 0.09 eV for the Au-Cu alloy by our procedure. This value agrees well with the experimental results (0.06). (author)