e-Induced secondary electron emission yield of insulators and charging effects

Based on a more realistic description of the in-depth secondary electron generation than that of standard (constant loss) model, a new model for the e-induced secondary electron emission yield, delta = f(E-0), is applied to account for the observed mean atomic number dependence of the reduced yield curves (RYC), delta/delta(max) = f(E-0/E-max(0)) of a wide variety of inorganic insulators. It is next used to extract and to discuss physical information on secondary electron escape probability and attenuation length of a number of oxides and alkali halides and to deduce their X-ray-induced secondary electron emission yield, delta(x) = f(hv). Extrapolation of experimental data above the few keV energy range including the estimate of the nominal critical energy E is also illustrated. Correlation between time dependence of charging and of secondary electron emission is next analyzed and various charging effects such as the observed negative charging when a positive charging was expected or the possible change of sign of the specimen current, are explained by the difference between E-2(0) and E-2(C) (critical energy obtained under permanent irradiation). Strategies to identify charging effects via their influence on the distortion of the yield curve and to reduce them are finally suggested. (c) 2005 Elsevier B.V. All rights reserved.