Back Scattered Electrons

Produced by elastic interactions of beam electrons with nuclei of atoms in the specimen

Energy loss less than 1 eV,

Scattering angles range up to 180°, but average about 5°

Many incident electrons undergo a series of such elastic event that cause them to be scattered back out of the specimen

The fraction of beam electrons backscattered in this way varies strongly with the atomic number Z of the scattering atoms, but does not change much with changes in .

Because of this dependence of on atomic number, images produced using BSE show characteristic atomic number contrast. That is, features of high average Z appear brighter than those of low average Z