Escape Mechanism of Secondary Electrons in Polar Crystals

Abstract

A simplified theory for the motion of secondary electrons produced inside a solid by electron bombardment is proposed. The Boltzmann transport equation is solved for scattering due to electron-phonon collisions. Forward scattering is found to be very predominant, and accordingly the scattering integral is greatly simplified if, further, a constant energy loss per collision can be assumed. Postulating also a form for the internal excitation function, the solution is obtained and applied to calculate the energy distribution, the angular dependence, and the dependence of the total external current on the electron affinity. Despite the oversimplified assumptions the model clearly shows the difference with the theories given for metals by Wolff and others. Several experimental features as observed on MgO are compatible with the theory.