ANGULAR-DISTRIBUTION OF ELECTRONS REFLECTED ELASTICALLY FROM NONCRYSTALLINE SOLID-SURFACES

The elastic backscattering of medium-energy (200-2000 eV) electrons from noncrystalline materials has been investigated experimentally, theoretically, and with a Monte Carlo (MC) technique. A theory for elastic electron backscattering has been developed. In this theory, singly scattering events are treated exactly while the double and higher order scattering processes are dealt with in the transport approximation. An analytical expression for the angular distribution of backscattered electrons has been derived. It has been shown that the contributions of singly and multiply scattered electrons are of the same order of magnitude. Therefore, the exact shape of the differential elastic cross section is of crucial importance for the interpretation of experimental data. The theoretical results are in good agreement with MC simulations in a broad range of electron energies and elements. Experimental data on the differential reflection coefficient in the energy range 300-1000 eV for polycrystalline Al, Ni, Pt, and Au for scattering angles ranging from 45 degrees to 135 degrees are presented. The measured angular distributions agree well with theory.