The orientation dependence of the electron backscattering coefficient of gold single crystal films

A theory is developed for calculating the orientation dependence of the backscattering coefficient of single crystal films. Three contributions are calculated separately; firstly the direct Lackscattering out of the Bloch wave field, secondly the backscattering of electrons scattered out of the wave field into angles smaller than 90° and thirdly the remaining fraction of electrons scattered into very small angles. The electron diffusion is considered by Monte-Carlo calculations. The results are approximated by simple analytical formulas for computation. The theory is compared with experiments on gold single crystal films on a mica substrate. For primary electron energies below 6 keV, a decrease of the orientation anisotropy of backscattering is observed with decreasing energy, whereas Si and Ge single crystals show a further increase. This decrease agrees with numerical calculations using cross sections for low energies.