Intercomparison of methods for separation of REELS elastic peak intensities for determination of IMFP

S. Tougaard, M. Krawczyk, A. Jablonski, J. Pavluch, J. Toth, D. Varga, G. Gergely, M. Menyhard, A. Sulyok

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Abstract

The consistency and accuracy of inelastic electron mean free paths (IMFPs) determined from comparison of the intensity of elastically reflected electrons with theoretical calculations were studied. The variation with experimental geometry, spectrometer energy resolution and the procedure for background subtraction was studied. Four different types of spectrometers - double pass cylindrical mirror analyser (CMA) pre-retarded CMA, hemispherical analyser (HSA) and retarding field analyser (RFA) - with widely different geometries and energy resolutions, placed in four different laboratories in three countries, were used. Four background subtraction methods (Shirley, linear, Tougaard and ELPSEP) were applied to isolate the elastic peak intensity from the reflected electron spectra. It was found that the IMFPs determined with data from the double pass CMA deviated considerably more (by a factor of 2) from the average values as well as from theoretical IMFP values than IMFPs determined with data from the other spectrometers. The data from the double pass CMA were therefore excluded from the statistical analysis. The root mean square (RMS) deviation of the IMFP from a function fitted to the data was 1.6-2.8 angstrom, depending on the background subtraction method, and it is smallest for the Tougaard method. The RMS deviation from IMFP values calculated by Tanuma et al. is 2.1-3.2 angstrom, again with the smallest value for the Tougaard method. The percentage deviation of the results using a Tougaard background from Tanuma et al. values is 12.6%. The results point to the conclusion that the major contribution to the inaccuracies in IMFPs determined with this method is not the background subtraction procedure but rather the lack of accuracy of the presently available models for elastic electron scattering, i.e. atomic elastic scattering cross-sections and effects of crystallinity that are not included in the presently applied models.

Original languageEnglish
Pages (from-to)1-10
Number of pages10
JournalSurface and Interface Analysis
Volume31
Issue number1
DOIs
Publication statusPublished - jan. 1 2001

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ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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