Secondary-electron-escape probabilities

Abstract

The probability B that a secondary electron internally excited in an insulator escapes upon reaching the surface is extracted from experiment and discussed theoretically for the first time. It is shown that B=2.5δmε/E0m, where ε is the electron-hole-pair creation energy and δm and E0m are the maximum secondary yield and the primary energy of maximum yield, respectively. It is also shown that ε=2.8Eg, where Eg is the insulator band gap. Values of B are extracted from secondary-electron-emission data for many semiconductors. A simple theory relating B to χ/Eg, the ratio of the electron affinity and the band gap is developed and shown to define an upper bound for the experimental data. The free-particle approximation adequately describes these hot- (energies ≳1 eV) electron phenomena.