The inelastic mean free path of electrons. Past and present research

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The inelastic mean free path (IMFP) is a fundamental material parameter. Presently the IMFPs calculated by the TPP-2M predictive formula (NIST SRD 71) are generally used. Elastic peak electron spectroscopy (EPES) is proved to be adequate for experimental determination of the IMFP denoted by λ e . λ e is smaller then λ i (TPP-2M) values, due to surface losses, characterized by the SEP (surface excitation) P se material parameter. The present research is focused on the experimental determination of P se based on Tanuma's work. The Tanuma factor f sT is the ratio of experimental I e and calculated I c elastic peak intensities I e ( E)/ I c ( E). The detection angle dependent I c is proportional to Δ Ω, the solid angle of detection. The angular I c ( E,Δ Ω, α d ) was calculated applying the EPESWIN software of Jablonski. In our work, experimental data of Goto were analysed for Si and Ni. Recent angularly resolved AREPES results of Jablonski and Zemek were quantified by fitting them at the 42° CMA (cylindrical mirror analyser) angle to absolute data of Goto and applying f sT. The models and SEP material parameters published by Werner et al., Ding et al., Kwei et al., Jablonski–Zemek and Nagatomi–Goto (Ni) and our data obtained by modifying Chen's data (Si) have been tested. The best approach was obtained using data of Werner for Si, and data of Nagatomi for Ni. The SEP corrected IMFPs λ eco were deduced. The EPES SEP parameters were valid for AREPES by averaging over α d = 35–70°. EPES spectra are quantified by applying the backscattering yield.