Determination of the inelastic mean free path of electrons in polyaniline samples by elastic peak electron spectroscopy

Abstract

Application of x-ray photoelectron spectroscopy, Auger electron spectroscopy and electron energy loss spectroscopy for quantitative characterisation of surfaces requires knowledge of the electron inelastic mean free path and its energy dependence. Inelastic mean free path values have been determined for a wide variety of solids using theoretical and experimental methods. However, the number of published inelastic mean free path values for polymers is limited. In principle, these values for polymers can be estimated using predictive formulae such as TPP-2M and the G1 formula of Gries. An alternative method for inelastic mean free path determination in polymers is elastic peak electron spectroscopy. In the present work, the surface chemical composition of polyaniline samples (undoped and doped with palladium) was analysed quantitatively using x-ray photoelectron spectroscopy. The inelastic mean free path values were determined by elastic peak electron spectroscopy using a high-energy-resolution hemispherical analyser in the energy range 500– 5000 eV. The resulting inelastic mean free path values evaluated using Ni and Ag standards are smaller than the values resulting from the G1 predictive formula of Gries and the TPP-2M predictive formula of Tanuma et al. The discrepancies in the inelastic mean free path values are discussed extensively. Copyright © 2000 John Wiley & Sons, Ltd.