Modeling Secondary Electron Imaging at Atomic Resolution Using a Focused Coherent Electron Probe

Consider the entrance surface of a specimen irradiated by primary fast electrons with energy of the order of 100 keV. Electrons are observed to be emitted from the entrance surface. Those with energies less than around 50 eV are the secondary electrons to which we refer [2]. Electrons with energies between around 50 eV and the energy of the incident electrons are mainly Auger electrons and thermally (Rutherford) backscattered electrons [2]. In the experiment of Zhu et al. [1] 85–90% of the electrons detected in the backwards direction had a kinetic energy between 0 and 50 eV, with most having an energy less than 10 eV. We assume that these low-energy electrons are predominantly the product of ionization events. For an atomically sized probe, localized (core-shell) ionization provides high resolution (bulk) atomic column positions.