Point Defect Studies in Gold by Electron Irradiation at Low Temperatures. I. Threshold Displacement Energy and Displacement Cross Section

The damage production on 99.999% pure 0.00025-in.-thick gold foils was measured as a function of incident electron energy in the range from 1.3 to 2.2 MeV. The effective threshold displacement energy was measured to be near 35 eV. It was found that reasonable agreement between the experimental and theoretical values of the displacement cross section could only be achieved with an unusually low value of the resistivity of a Frenkel pair (${\rho }_F=0.89\mathrm{}\times {10}^{-4\mathrm{}}$ Ω-cm/unit fractional concentration). By comparison, in copper the agreement between the theoretical and experimental cross section (${\rho }_F=1.2\mathrm{}\times {10}^{-4\mathrm{}}$ Ω-cm/unit fractional concentration) is somewhat better. This is interpreted to indicate that directional effects in the displacement process are considerably more important in gold than in copper, and that, for energies near the threshold energy, displacements in gold are possible only in a small solid angle centered about one crystallographic direction, most likely the $〈100〉$ direction.