High energy primary electron that suffers large angle (> 90°) scattering and re-emerges from the entry surface of a specimen. Backscattered electrons usually have energies close to that of the primary electron beam. They are valuable in microanalysis because their number depends on the average atomic numberA number equivalent to the number of protons in the nucleus of an atom, commonly abbreviated as Z. of the sample.
Compositional variations (variations in average Z) can be imaged by mapping backscattered electron intensities.
Some or all content above used with permission from J. H. Wittke.