Investigation of frenkel defects in low-temperature e −-irradiated mg by diffuse x-ray scattering

Publisher Website
Google Scholar
Abstract
Mg single crystals were irradiated with 3 MeV electrons at 4.5 K producing electrical resistivity changes varying between 83 and 232 nΩcm. Diffuse X-ray scattering measured at (00.h) and (h0.0) or (hh.0) Bragg reflections showed defects with a large relaxation volume of ΔV rel ≈ 5 atomic volumes and a very anisotropic long range displacement field. Contrary to hcp Zn and Cd, these displacements were larger within the basal plane than along the c-direction. Although it cannot be definitely excluded that these parameters describe the self-interstitial atom in the crowdion configuration, a more consistent explanation of all results is obtained with the assumption that agglomerates of 2–3 interstitials are formed by interstitial migration during the 4.5 K irradiation. In contrast to stage II irradiations of other metals no dose dependence of the agglomerate size was found. This unique behaviour is explained by a nucleation barrier for the interstitial agglomerates at the irradiation temperature. During thermal annealing, however, a slow and steady increase of the cluster size is observed corresponding to an average cluster size of about 6 interstitials at the end of annealing stage II (90 K).