The Location of Displaced Impurity Atoms in Irradiated Aluminum Crystals by Backscattering

The energy spectra of 1 MeV He+ ions backscattered from single crystals of Al alloys containing 0.09 at.% Mn, 0.09 at.% Zn, 0.08 at.% Ag, or 0.03 at.% Sn have been examined in different crystallographic directions. For the annealed crystals, the minimum yield of back-scattered He+ ions from Al atoms at 40 K in a direction was , and the corresponding yield from Mn, Zn, or Ag impurity atoms was (χmin)i ≤ 0.06, indicating that at least 96% of these impurity atoms had replaced Al atoms at normal lattice sites. For the Al–0.03 at.% Sn alloy, the substitutional fraction of Sn atoms was only ~50% for a slowly cooled crystal, but was increased to ~90% by a rapid (water) quench from 600 °C. Irradiation of the crystals at 40–70 K with 0.3–1.0 MeV He+ ions to doses of 1015–1016/cm2 caused the Mn, Zn, and Ag atoms to be displaced from lattice sites by the trapping of self-interstitial Al atoms. From an analysis of , , {100}, and {111} channeling, it was shown that the trapping configuration was the dumbbell. Both the...