Transmission electron microscopy and xhyphen;ray diffuse scattering have been used to study defect clusters in 4hyphen;MeV selfhyphen;ionhyphen;irradiated (total doses of 2.5times;1013and 5.0times;1013ions/cm2) nickel. The distribution of defect clusters as a function of the ion penetration depth was measured directly in the electron microscope using a transverse sectioning technique. For an ion dose of 2.5times;1013cmminus;2, the average cluster radius of 32plusmn;2 Aring; at the damage peak depth (0.82 mgr;m) was 20percnt; larger than the average radius near the crystal surface. The fraction of point defects created in the displacement cascades that survived in the form of defect clusters was found to be about 1percnt; for these doses. Annealing at 125, 250, and 450thinsp;deg;C gave a monotonic decrease in the number of point defects stored in the form of loops.
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