Point Defect Clusters in Electron-Irradiated Gold

Defect formation in gold by the irradiation of 2.0∼2.5 MeV electrons was studied with a high voltage electron microscope. The formation of dislocation loops by the aggregation of interstitials generally precedes the formation of the defects by vacancies. Permanent sinks, such as specimen surfaces and dislocations, prevent the formation of interstitial type of defects and enhance the formation of vacancy clustered defects. A rapid formation of the vacancy type defects and the simultaneous shrinkage of interstitial type loops after the cessation of the irradiation are observed. Kinetics analysis of the point defect behaviour, standing on the random migration of interstitials and vacancies, explains all the observed various phenomena as the competition processes between two kinds of point defects under various circumstances. The irradiation intensity dependence of the density of interstitial type defects shows that the di-interstitials are their stable nucleus.