Structure and radiation damage behavior of epitaxial CrxMo1−x alloy thin films on MgO

Phenomena related to the interaction of point defects and dopants with grain boundaries and interfaces have been very well documented. However, a quantitative understanding of such an interaction is still missing. In this paper we explore the correlation between radiation damage and interface structure. In doing so, CrxMo1−x (0 0 1) films of thickness ∼100 nm were epitaxially grown on MgO (0 0 1) using molecular beam epitaxy. The interface dislocation density can be systematically varied by controlling the composition of the film. This system allows us to probe the response of the defects generated during the irradiation to the interface dislocation density. The microstructural features of these films before and after irradiation are carefully studied using high resolution scanning/transmission electron microscopy and electron diffraction. It has been found that the film/substrate system is very resistant to ion-induced irradiation damage. No visible point defect clusters, dislocation network or amorphization has been identified, which is contrasted with other materials of either metallic or ionic bonding. In combination with RBS analysis, we conclude that the defects in the present system appear to be very mobile and were annihilated during the irradiation process.