Compositional dependence of radiation damage in ion-irradiated amorphous Ni-B

${\mathrm{Ni}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{B}}_{\mathrm{x}}$ amorphous films prepared by room-temperature ion implantation in the concentration range 0.20≤x≤0.34 are irradiated at 20 K with 100-keV ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ and 510-keV ${}_{}{}^{86}{}_{}{}^{}\mathrm{Kr}$ ions. The radiation damage is studied at 4.2 K by in situ resistivity experiments and during annealing up to 325 K. It is shown that the nature of the damage depends on the alloy composition. At low B content the increase of resistivity is interpreted in terms of localized defect creation, while at high B content the decrease of resistivity is ascribed to the creation of disordered zones (i.e., free volume). The latter process is enhanced when displacement cascades are induced by irradiation.