Spatial distribution of backscattered electrons in the scanning electron microscope and electron microprobe

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Abstract
Monte Carlo calculations have been applied to the electron scattering theory in scanning electron microscopy. These calculations are based on a single‐scattering model in which the screened Rutherford expression for single‐scattering cross section and the continuous energy‐loss equation of Bethe are used. The surface distribution of backscattered electrons is obtained for Al and Au targets at 20 keV, with 0° and 45° incidence. From these results the exit areas of the backscattered electrons are discussed and compared with experiment. The penetration depths of the backscattered electrons are given at 0° incidence. Everhart's model for backscattering was modified, taking into account the calculated results. The proportion of the singly backscattered electrons to the total backscattered electrons was estimated by the modified model. The result shows that about half of the total backscattered electrons are caused by large‐angle single‐scattering events. This is consistent with the previous results of Cosslett and Thomas.