Effect of cascade energy density on the defect cluster type in heavy-ion-irradiated gold

Abstract

For the quantification of defect production by energetic displacement cascades in metals, a knowledge of the types and numbers of defects created is required. In Au a considerable fraction of the defects generated in such cascades is present in large enough clusters to be observed by transmission electron microscopy (TEM) and analysed as to their structure, sizes, and types (interstitial or vacancy clusters). Heavy ion bombardments have provided an efficient means to study the defect production in cascades as a function of cascade energy. An important problem concerns the question whether visible interstitial clusters are formed in individual displacement cascades in addition to the vacancy clusters that are formed by collapse of the depleted zones. Two conditions may enhance the formation of interstitial clusters formed in cascades:1) An increase in displacement density as produced by overlapping two low energy cascades is expected to lead to a higher interstitial concentration in close vicinity of the depleted zones.