Mobility of interstitial defects in gold bombarded with 270 ev gold ions in stage III

Abstract

Shrinkage of vacancy stacking-fault tetrahedra in gold foils bombarded with 270 ev gold ions at temperatures between -90°c and +100°c was studied using transmission electron microscopy. In this work interstitial defects were produced by replacement collision sequences initiated near the incident surface. The tetrahedra were partially annihilated by absorbing these defects and therefore served as indicators for long-range interstitial migration. By comparing the same tetrahedra in high resolution micrographs taken before and after bombardment, and after subsequent annealing, it was possible to determine unambiguously the tetrahedron shrinkage as a function of foil thickness. It was found that (1) the tetrahedron shrinkage was independent of bombardment temperatures over the range -90°c to +100°c and (2) no shrinkage of tetrahedra or intrinsic Frank loops, or growth of interstitial clusters, occurred when foils bombarded as low as -90°c were warmed to +30°c. Several additional specimens bombarded with 180 ev argon ions gave similar results. These results disagree with and supersede the previous work by Venables and Balluffi (1965 a, b). Various interstitial mobility models are considered. It is concluded that the interstitials are already mobile at the lowest temperatures investigated, i.e. at -90°C.