Low Temperature Electron Irradiation Studies in Metals

Polycrystalline platinum and palladium were bombarded with monoenergetic electrons at temperatures below 9K. Changes in electrical resistivity R(E) = delta rho/electron-sq cm were measured in the energy range 1.1 to 3.0 MeV. The experimental values found in this interval are consistent with displacement threshold energies of 37 eV for Pt and 34 eV for Pd. The resistivities per unit defect concentration were found to be 0.00075 and 0.0009 ohm-cm for Pt and Pd respectively. The threshold energies found here, together with values reported for other face centered cubic elements, are shown to be directly proportional to atomic number and inversely proportional to the lattice parameter. It is also shown that the resistivities per unit defect concentration can be correlated with the resistivity at 0C. Analysis of the energy dependence of the damage production indicates atomic displacement cascades are markedly inhibited, which is consistent with deuteron damage studies. Alternative multiple displacement models and possible mechanisms are discussed. (Author).