Fundamental aspects of ion beam mixing

Irradiation of solids with energetic particles results in the reorganization of constituent target atoms, i.e., ion beam mixing (IM). At low temperatures, IM is characterized by prompt (10^-10 s) diffusion processes which are localized in the vicinity of the displacement cascade. Mixing at low temperatures can cause the system to depart far from the equilibrium state. At elevated temperatures, the diffusion of radiation-induced defects extends the mixing to longer times and greater distances. These delayed IM processes tend to return the system toward equilibrium. Recent experimental progress has led to a qualitative understanding of the fundamental aspects of IM in both temperature regimes. This has been achieved through systematic measurements of the influence of temperature, dose, dose-rate, cascade energy density and chemical interactions on IM. The results of these experiments will be reviewed and compared to IM models based on collisional, thermal spike and radiation-enhanced diffusion processes. The relation of IM to other fundamental radiation damage effects will also be discussed.