Interstitial clusters observed below stage III annealing in electron irradiated pure gold

Abstract

Pure gold specimens were irradiated at 130°K with 3 Mev electrons. The total flux was from 1·2 to 6·0 × 10¹⁸ e/cm². At temperatures below stage III annealing, a large number of interstitial loops were observed in irradiated specimens by electron microscopy. The number of loops decreased with increasing purity and was independent of the electron flux. The number was 8 × 10¹⁴ cm⁻³ for 99·9999% purity and 2 × 10¹⁶ cm⁻³ for 99·999% purity. Their size was larger in purer specimens and increased with increasing total flux. Typical average sizes of defects in 99·9999% pure specimens were 46 Å (260 interstitials per cluster) and 72 Å (660 interstitials per cluster) for 1·2 × 10¹⁸ and 6·0 × 10¹⁸ e/cm², respectively. These clusters, even the smallest observable ones of 10 Å in size, were quite stable and never broke up near room temperature. They shrank and disappeared completely, however, in bulk specimens during stage III annealing. Evidence showing the importance of the strain field of interstitial loops was found for the vacancy annihilation during stage III annealing. The experimental results can be explained by supposing that lattice vacancies migrate in stage III.