Defect production in ion-irradiated aluminum

Residual-resistivity measurements on ion-irradiated thin films are used to study defect production in aluminum. The energy and mass dependences of damage rates indicate that defect production efficiency (relative to the modified Kinchin-Pease relation) strongly decreases at recoil energies between 5 and 10 keV. At high energy the efficiency approaches an asymptotic value of 0.5. These results are similar to those observed in copper and silver. Binary-collision simulations were performed for copper, silver and aluminum to investigate the relationship of cascade structure to defect production efficiency. The mechanism primarily responsible for the reduced defect production efficiency in cascades in aluminum is thought to be the subthreshold recombination of Frenkel pairs during the thermal-spike phase of the cascade.