Stage III Annealing in Proton-Irradiated Noble Metals

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 Δρ₀=3×10^-9 cm to Δρ₀=3×10^-8 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 EM^_III (Cu)=0.71 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.