Stage III Annealing in Proton-Irradiated Noble Metals

Abstract

Pulsing and annealing data are given for 99.999% pure copper specimens which have been proton irradiated at 90°K. It is shown that stage II obeys first-order annealing kinetics and that the structure observed is probably not associated with impurities. Stage III obeys second-order kinetics, and its activation energy in the case of copper is not dependent on dose in the range $\Delta {\rho }_0=3\mathrm{}\times {10}^{-9\mathrm{}}$ cm to $\Delta {\rho }_0=3\mathrm{}\times {10}^{-8\mathrm{}}$ cm. Pulsing experiments in which samples are heated in a msec from -50°C to temperatures up to 230°C and held for 30 msec before quenching show no evidence for any change in the annealing process (i.e., the results can be predicted assuming $E_M^{}{}_{}{}^{\mathrm{III}} \left(\mathrm{Cu}\right)=0.71\mathrm{}$ eV and using second-order kinetics). It is shown that if di-interstitial migration is responsible for stage III then the binding energy of di-interstitials exceeds 1.0 eV in copper. If, conversely, two kinds of interstitials migrate in stages I and III, then the pulsing experiment suggests that the barrier preventing conversion of the stage III type to the stage I type is greater than 1.14 eV in copper. No evidence for vacancy migration in proton-irradiated silver is observed during annealing at temperatures above stage III. Existing models suggested to explain the annealing of irradiation damage are reviewed.