Defect clustering in copper, silver and aluminum during heavy-ion irradiations at low temperatures

Point defect clustering during heavy-ion irradiation at low temperature was investigated in copper, silver, and aluminum using electrical-resistivity measurements. Clustering effects were studied by determining the average recombination volume per Frenkel defect, V, as a function of defect concentration. Within single unoverlapped displacement cascades, the clustering increased with increased energy density in the cascades. For Ar-irradiated aluminum no clustering was observed in individual cascades, whereas for Kr-irradiated silver V was deduced to be V 0.2 Vo, where Vo is the value of V for unclustered defects. Clustering was observed for all ion-target combinations at sufficiently high dose. For copper and silver at high doses, a regime was reached in which additional irradiation increased the Frenkel defect number N without increasing the total recombination volume N V. Defect clustering in copper and silver during isochronal annealing of damage produced by 150-keV proton irradiation was investigated by the same method.