Depth profiles of nickel ion damage in helium-implanted nickel

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Abstract
The depth dependence of microstructural damage and swelling in pure nickel during nickel-ion bombardment at 0.51 Tm is measured and is compared with the predictions of the E-DEP-1 code. Cavities are developed to depths 30 to 40° greater than the maximum depths calculated for a significant level of displacement events. It is argued that diffusional spreading of point defects contributes to this extension. A helium distribution superimposed on the heavy ion damage profile greatly increases nucleation of cavities and reduces their growth. The swelling profile is modified in a complex manner by the local concentration of helium and by the method of implanting it. In general, helium preimplanted at room temperature strongly over-stimulates cavity formation causing enhanced swelling at low heavy ion dose and depressed swelling at high dose. Helium implanted simultaneously with heavy ion damage gives more gradual promotion of cavities and continuously increasing swelling with dose. A band of deep dislocations is found at twice the predicted maximum depth for damage, and is attributed to relief of the nonuniform swelling by plastic deformation.