Thin films of nanocrystalline material were deposited onto liquid-N cooled substrates by using electron beam techniques; thus giving a grain size of about 8nm. Some of the films were annealed (773K, 1h) to give a second set of films with a grain size of about 40nm. These 2 sets of films, nanocrystalline and polycrystalline, were bombarded with 1MeV Xe2+ and 500keV Ar+ ions to doses of up to about 10dpa. Changes in the electrical resistivity and its temperature dependence were measured. A relatively small resistivity contribution due to grain-boundary scattering was detected which furnished no evidence for the existence of a highly disordered grain-boundary phase. The temperature-dependent part of the resistivity was found to be very similar to that of the pure bulk metal. This suggested that the nanocrystalline thin films and bulk material had the same characteristic Debye temperature of 185K. The saturation level for irradiation-induced defects at room temperature was found to be similar for nanocrystalline and polycrystalline thin films. The same saturation concentration, corresponding to a resistivity increase of about 1cm, was found for both Xe and Ar irradiation to doses of more than 1dpa. A change in the temperature dependence of the resistivity was found after ion irradiation. This change was consistent with an irradiation-induced reduction of 20% in the characteristic Debye temperature to 150K.

N.Karpe, G.Lapogian, J.Bøttiger, J.P.Krog: Philosophical Magazine B, 1995, 71[3], 445-56