The backscattered electron coefficient is known to be primarily dependent on the atomic number of the sample. If the atomic number increases, the backscattered electron coefficient increases, which results in a higher intensity in the backscattered electron image. The dependence of the primary electron energy is somewhat more complicated. Using photographic material (with composition AgBr-AgI), it is seen that the contrast in the backscattered electron image increases with the primary electron energy. Using three independent methods, based on image analysis techniques, it is shown that the difference between the backscattered electron coefficient of AgBr and AgI increases with the primary electron energy in the range from 40 to 100 keV.
Geuens, I.; Nys, B.; Naudts, J.; Gijbels, R.; Jacob, W.; and Van Espen, P.
"The Primary Energy Dependence of Backscattered Electron Images Up to 100 keV,"
Scanning Microscopy: Vol. 5
, Article 5.
Available at: https://digitalcommons.usu.edu/microscopy/vol5/iss2/5