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

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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, δ = f( E 0), is applied to account for the observed mean atomic number dependence of the reduced yield curves (RYC), δ / δ 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, δ X = f( hν). Extrapolation of experimental data above the few keV energy range including the estimate of the nominal critical energy E 2 0 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.