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

B. Lesiaka, A. Kosińskia, A. Jablonskia, A. Sulyokb, G. Gergelyb, J. Tóthc and D. Vargac aInstitute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warszawa, Poland bInstitute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, 1545 Budapest, Hungary cResearch Institute for Nuclear Physics ATOMKI, Hungarian Academy of Sciences, P.O. Box 51, 4001, Debrecen, Hungary

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Received: 11 07 2005; revised version: 20 01 2006; in final form: 14 03 2006;

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.

DOI: 10.12693/APhysPolA.109.789 PACS numbers: 82.35.Cd, 82.80.Pv, 87.16.Ac