 Backscattered electron

A backscattered electron is a primary beam electron redirected out through the incident side of a specimen after scattering. Backscattered signals commonly retain much more of the incident kinetic energy than emitted low-energy secondary electrons.^[ref]

In a scanning electron microscope, collecting these electrons can provide backscattered-electron atomic-number contrast, but specimen tilt, collection geometry and crystallographic electron channeling also change brightness. Comparing detector directions or tilting the specimen tests some of those contributions. A bright region is therefore not uniquely a region of greater atomic number.