Comparisons of radiation damage in He ion and proton irradiated immiscible Ag/Ni nanolayers

We compare the evolution of microstructure and mechanical properties of Ag/Ni multilayers of varying layer thickness (1-200 nm) subjected to helium ion and proton irradiation at room temperature to similar dose, ∼2 displacements-per-atom on average. Layer structure remained intact after both types of irradiation although defects accumulated in the layers are different. Helium bubbles were the major defects in helium ion irradiated films, while dislocation loops were ubiquitous in proton irradiated multilayers. In He ion irradiated multilayers, radiation hardening was greater than that in proton irradiated specimens, and the magnitude of hardening decreased with decreasing individual layer thickness. In comparison no size dependent hardening was observed in proton irradiated films. Mechanisms of irradiation induced hardening were discussed.