Formation of vacancy clustered defects from cascade collisions during heavy-ion irradiation and their annihilation by freely-migrating interstitial atoms

Abstract

Heavy-ion irradiation of several fcc metals and their ordered alloys was performed. The behavior of ion-irradiation induced point defect clusters during subsequent electron irradiation indicates that about 90% of the clusters are of vacancy type and 10% of interstitials. For any given ion and energy, a wide variation of the collision cascade zone size was found. In general, the larger zones were associated with a larger number of point-defect clusters. A collision zone of a given size was associated with the same average number of clusters even when they were produced by ions of different energy. The dependence of cluster formation on ion energy, target material, and angle of incidence of the ion beam can be correlated with a unique parameter, the depth in the foil of defect cluster formation. The defect yield increases linearly with irradiation dose for shallow depth distributions but then increases with a square-root relationship for deeper distributions. These results are analyzed in terms of a variation in the role of freely-migrating interstitials for the two cases.