ABSTRACT
Most materials in the human environment are insulators. The absence of conduction electrons in monocrystalline insulators may explain the fact that these materials have, at least at the initial stage of the irradiation, a secondary electron yield of about one order of magnitude greater than that of metals. The absence of electron-electron interactions increases the attenuation length of the emitted secondary electrons. The electrostatic approach explains at least qualitatively the main aspects of charging and the spurious effects that may occur during the investigation of insulating materials by incident electron beam techniques. The problem of irradiation by light and mobile particles such as electrons is more difficult. The electron-hole pairs generated by photoabsorption induce a surface photoconductivity which allows excess charge to flow to earth. If the electrostatic approach is considered in more detail for electron irradiation, it is necessary to obtain more information on the trapping mechanism for electrons.
