The Effects of Repeated Electron Irradiation for the Formation of Interstitial Loops in Pure Aluminum

Abstract

In an electron microscope, pure aluminum foil was irradiated at 120°C with 200 keV electrons to form interstitial loops and then heated at 200°C to anneal them out. When such a process was repeated many times on the same position of a specimen, the number density of interstitial loops (I-loops) decreased with increasing number of repeats. In a specimen whose number density of I-loops had already decreased greatly by repeated irradiation at l20°C, the relation between the number density of I-loops and the irradiation temperature was examined from -160°C to 120°C. Above 0°C, the number density of I-loops was smaller than that of a freshly irradiated specimen. Below 0°C, it was the same as that of a freshly irradiated specimen. These results are interpreted as meaning that an I-loop nucleates at an impurity cluster above 0°C, whereas it does so at a single impurity below 0°C.