NANOCRYSTALLINE ION-IRRADIATED GOLD ELECTRICAL-RESISTIVITY USED TO STUDY DEFECTS AND GRAIN-BOUNDARIES

Thin films of nanocrystalline gold have been prepared by electron-beam deposition on to liquid-nitrogen cooled substrates, giving a grain si ze of about 8 nm. Some of these films were annealed at 773 K for 1 h, giving a second set of films with a grain size of about 40 nm. These t wo sets of films, denoted nanocrystalline and polycrystalline, were io n irradiated using 1 MeV Xe2+ and 500 keV Ar+ with doses up to about 1 0 displacements per atom. Changes in the electrical resistivity and it s temperature dependence were measured. A relatively small resistivity contribution due to grain-boundary scattering was observed, giving no evidence for a strongly disordered grain-boundary phase. The temperat ure-dependent part of the electrical resistivity was found to be very similar to that of pure bulk gold, suggesting the same characteristic Deby temperature for nanocrystalline thin films and bulk gold (185 +/- 10 K). The saturation level for irradiation-induced defects at room t emperature was found to be similar for the nanocrystalline and polycry stalline thin films. The same saturation concentration, corresponding to a resistivity increase, DELTArho, of about 1 muOMEGA cm, was found for both Xe2+ and Ar+ irradiation for doses larger than 1 displacement per atom. After ion irradiation, a change in the temperature dependen ce of the electrical resistivity was found. This change is in agreemen t with an irradiation-induced reduction by 20% of the characteristic D ebye temperature to 150 +/- 10 K.