The extent of electron backscattering increases at low accelerating voltages of the incident electron beam. Figure 2928 shows Monte Carlo simulation of backscattered and absorbed electrons in Al (aluminium) with 7 keV and 4 keV incident electron beam. Both the interaction volumes of the backscattered and absorbed electrons for 4 keV are smaller than those for 7 keV. The depths of backscattered electrons are ~140 nm and ~ 50 nm, respectively.
|Figure 2928. Monte Carlo simulation of backscattered and absorbed electrons in Al with 7 keV and 4 keV incident electron beam (red: backscattered electrons, and blue: absorbed electrons). 
 Jorg Nissen and Dirk Berger, Lateral resolution of quantitative element analysis of low-Z elements, https://doi.org/10.1002/9783527808465.EMC2016.6229.