Point-Defect Studies in Platinum by Electron Irradiation at Low Temperatures. I. Defect Production

The electrical resistivity increase per unit electron flux (damage rate) of 99.999%-pure 0.0002-in.-thick platinum foils was measured as a function of incident electron energy from 1.3 to 2.1 MeV near 9°K. Reasonable agreement between the theoretical displacement cross section, calculated with a unit displacement probability, and experimental data is achieved with an effective threshold displacement energy of 36 eV and a Frenkel resistivity of 6×${10}^{-4\mathrm{}}$Ω cm per unit fractional concentration Frenkel pairs. The ratio of the damage rate of platinum to that of gold is nearly independent of the electron energy for $45 \mathrm{eV}<T_m<72\mathrm{} \mathrm{eV}$ and decreases rapidly to zero for $T_m<45\mathrm{}$ eV, where $T_m$ is the maximum energy imparted to a lattice atom by a bombarding electron. These results are interpreted to indicate that indirect displacement processes occur in both metals near threshold.