Anisotropic cross sections in low-energy electron-reflection spectroscopy on solids

We discuss the experimental conditions for the detection of anisotropies in the elastic and inelastic cross sections of low-energy electrons (1–30 eV) backscattered from solid films. We use an n-flux matrix approach to study the electron transport in the bulk of the films. We find that anisotropic inelastic cross sections can sometimes be detected visually in the multiple-loss backscattered currents when there is but a single dominant loss mechanism. Better yet, anisotropy breaks the azimuthal symmetry of the backscattered current for non-normal incidence and can thus easily be detected by looking for a dependence of this (nonspecular) current on the angle between the incident and detection planes (planes including the direction normal to the film surface). The sensitivity is largest when the source and detector axis make a large angle with respect to the normal to the film.