Ion-irradiation studies of the damage function of copper and silver

Abstract

A systematic study of the damage function of both Ag and Cu has been performed by measuring resistivity increments induced by irradiation of thin-foil specimens at 6 K with several species of ions. Beam energies were selected such that the projectiles were stopped within the target. Results were compared with theoretical calculations based on a modified Kinchin-Pease damage function. The damage efficiency (ratio of experimental-to-theoretical values) is roughly unity for irradiations with H, but decreases rapidly as the projectile mass increases, which results in harder recoil spectra. For projectiles heavier than Ne, the efficiency becomes relatively constant (0.4 for Ag and 0.35 for Cu). These results indicate that deviations from the modified Kinchin-Pease model begin to occur at energies not far above the displacement threshold energy and the efficiency becomes roughly constant for recoil energies greater than a few keV. Comparison is made with damage-rate studies for other types of irradiation.