Influence of irradiation temperature on self-ion damage in copper

The damage structure produced in copper crystals by irradiation with 30 keV self ions in the temperature range 20°-425°C has been studied by means of transmission electron microscopy. The incident ions generate displacement cascades and the vacancy-rich centres of such cascades collapse to form vacancy loops. The number of visible loops remains constant for irradiation temperatures up to 300°C but decreases sharply at higher temperatures. This behaviour can be accounted for by a model in which loop shrinkage is increasingly controlled by loop loss due to thermal vacancy emission-controlled shrinkage. Preliminary results are also presented showing how defect geometry is influenced by irradiation temperature.