Influence of Recoil Effect and Surface Excitations on the Inelastic Mean Free Paths of Electrons in Polymers

Abstract

In this work, the influence of recoil effect and surface excitations on the inelastic mean free paths for polythiophenes is investigated. The inelastic mean free paths of electrons in polythiophenes are measured with the elastic peak electron spectroscopy method using the Ag standard and the electron elastic scattering cross-sections from the database NIST 3.1 in the electron kinetic energy range 200-5000 eV. The Monte Carlo model is applied for evaluating the electron backscattering intensities from the polymers and the Ag standard, as well as for evaluating electrons quasi-elastically backscattered from atoms of different atomic numbers (the recoil effect). The surface excitation corrections are accounted for using the formalism of Chen, with the material parameters for polythiophenes evaluated from the elastic peak electron spectroscopy method. Deviations due to recoil effect and surface excitations to the inelastic mean free paths are compared and discussed. Correction to the inelastic mean free paths due to recoil effect is considerable but is smaller, however, than the correction due to surface excitations. Accounting for recoil effect and surface excitations leads to improvement of the inelastic mean free paths, as compared to the inelastic mean free paths resulting from the predictive formulae of Gries.

Morphology, surface roughness, electron inelastic and quasielastic scattering in elastic peak electron spectroscopy of polymers

“…A comparison of the influence of surface excitation corrections and recoil on hydrogen on the elastic peak intensity (for evaluating the accuracy of IMFPs derived by EPES) has been made for selected polythiophenes. 7 Correction due to surface excitation was found to be larger than that due to the recoil effect on hydrogen. 7 In the present work, the influence of different factors (surface morphology, roughness, surface excitations and recoil on hydrogen) on the electron elastic peak intensity is compared for exemplary polymers, such as polyethylene and polyaniline.…”

“…7 Correction due to surface excitation was found to be larger than that due to the recoil effect on hydrogen. 7 In the present work, the influence of different factors (surface morphology, roughness, surface excitations and recoil on hydrogen) on the electron elastic peak intensity is compared for exemplary polymers, such as polyethylene and polyaniline. The surface morphology and roughness is characterized by atomic force microscopy (AFM), the bulk density is analyzed using the helium pycnometry method and the atomic surface composition is determined by X-ray photoelectron spectroscopy (XPS).…”

“…surface excitations, 4 -7 and electron quasielastic scattering on hydrogen atoms (recoil effect). 7 Evaluation of IMFPs in EPES is based on the measurement of electron elastic backscattering probability, i.e. the intensity of elastic peak, and on Monte Carlo (MC) simulations of the electron transport in a solid.…”

“…2 The measured intensity of the elastic peak can be affected by surface morphology, roughness, porosity, 8 -10 surface excitations 4 -7 and recoil effect. 7 Morphology and surface roughness can be defined by a number of parameters, of which the most important parameters are the average mean deviation (ar), the spacing discrimination (c) and the mean width of profile elements of the assessed profile (mp). 11 They have proved to be of practical value for irregular polymer surfaces.…”

The Inelastic Mean Free Path οf Electrons. Research in Budapest, Warsaw, Wrocław and Clermont-Ferrand. Brief History and New Results

“…Our paper is confined to IMFP-EPES experiments, carried out in Budapest (CMA), Warsaw (double-pass CMA), Clermont-Ferrand (RFA and HSA), Lyon (HSA), Debrecen (ESA-31), Odense (HSA) and Prague (RFA). Results on metals, semiconductors, polymers [11] are summarized in [2].…”