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Extracting the dielectric function from high‐energy REELS measurements
Author(s) -
Vos Maarten,
Grande Pedro L.
Publication year - 2017
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.6227
Subject(s) - dielectric , drude model , reflection (computer programming) , refractive index , function (biology) , computational physics , dielectric function , relaxation (psychology) , electron , energy (signal processing) , dielectric loss , excitation , optics , statistical physics , physics , quantum mechanics , computer science , psychology , social psychology , evolutionary biology , biology , programming language
A method is described for extracting the dielectric function directly from a reflection electron energy loss spectrum taken at relatively high energies (2.5 to 40 keV). It makes simplifying assumptions on separation of surface and bulk losses. The approach uses a description based on partial intensities and surface excitation parameters and fits directly the reflection electron energy loss data. Several different model dielectric functions are implemented (extended Drude, Drude Lindhard, Mermin, and the Levine–Louie dielectric functions with relaxation time), and their advantages and disadvantages are discussed. Justification of this approach is in the end based on a comparison with the dielectric function as obtained by other means, which is generally quite good, provided that the solution obtained is restrained by sum rules to the right refractive index and electron density. The fitting program, to be used in conjunction with commercial plotting software, is provided. Copyright © 2017 John Wiley & Sons, Ltd.