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

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The inelastic mean free paths (IMFPs) of three AuPd alloys were determined by means of elastic peak electron spectroscopy (EPES) in a round-robin study in four laboratories using different types of electron spectrometers in the energy range 0.5-2 keV. The scatter of the IMFP values was in the range of 25%. Within this accuracy the inverse IMFP of these alloys can be calculated by the weighted sum of the inverse IMFPs of the alloying elements. Reflected electron energy loss spectra also were measured and the Kl curves, calculated by the method of Tougaard, were used for estimating the inelastic processes in the alloys. The source of the scatter in the IMFPs obtained in the present work is discussed.

Section: Evaluation Procedures Elastic Peak Electron Spectroscopy Bacmentioning

confidence: 99%

Determination of inelastic mean free paths for AuPd alloys by elastic peak electron spectroscopy (EPES)

Krawczyk

Jabłoński

Zommer

et al. 2002

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“…Background of the EPES spectra was subtracted by the elastic peak separation procedure (ELPSEP) method 34 prior to further processing and elaboration.…”

Section: Methodsmentioning

confidence: 99%

Experimental and model study of the Rh/Al system by means of EPES

Pavluch

Zommer

Polyak

et al. 2005

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The Rh/Al system has drawn significant attention as a model heterogeneous catalyst due to its unique adsorption properties. In this study, a set of samples consisting of Al substrates made of polished and etched pure metal sheets and deposited in situ with ultrathin Rh overlayers of different thickness was prepared. During the preparation of the samples, in-depth diffusion of Rh into the surface region of Al substrates obviously took place. To quantify this process, i.e. by non-destructively ascertaining the resulting depth profile of the samples, elastic peak electron spectroscopy (EPES) was employed. An EPES measurement was performed for energies of 500, 750 and 1000 eV with the initial Rh overlayer thickness in the range 3-20Å and using pure Rh and Al standards. The measurement was carried out on a precision spherical retarding-field analyser (RFA). The resulting experimental EPES intensities, as a function of the primary energy and the initial thickness of the Rh overlayer, were compared and fitted with the intensities simulated by the Monte Carlo (MC) method. An MC model of the sample surface consisting of three regions of different inelastic mean free path (IMFP) and Rh concentration were assumed: the first -Rh on the substrate top, the second -Rh/Al with exponential decay of Rh in Al and the third -pure Al. The best fit and best consistency for different primary energies were achieved under the assumption that no Rh was left on Al substrate top, but an exponentially decaying profile of Rh in Al was created at the surface.

“…The IMFP values shown in Fig. 5 are taken from the compilation published by Tougaard et al 35 (the CMA data).…”

Section: Calculation Of the Imfpmentioning

confidence: 99%

“…These options were selected on the basis of good performance in the interlaboratory study of the background removal methods. 35 Finally, the user has a possibility to create and save different files with calculated information.…”

Section: Software Packagementioning

confidence: 99%

“…As a compromise between reliability of a physical model and mathematical convenience, Tougaard proposed a method described by the acronym ELPSEP (ELastic Peak SEParation method). 34 A detailed algorithm of the ELPSEP method (and also other methods of background separation) has been described by Tougaard et al 35 Four background separation methods were submitted to statistical analysis in the Round Robin experiment in which the same samples were studied in several laboratories using spectrometers with different geometries and energy resolution. 35 It has been found that the best performance (smallest scatter of the obtained IMFP values) has been observed for the Tougaard background.…”

Section: Spectra Processingmentioning

confidence: 99%

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Determination of the electron inelastic mean free path in solids from the elastic electron backscattering intensity

Jabłoński

2005

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The inelastic mean free path (IMFP) of electrons in solids is an important parameter needed for quantitative applications of electron spectroscopies: X-ray photoelectron spectroscopy and Auger electron spectroscopy (AES). The IMFP values published for compounds or alloys are rather limited, and in general case, the predictive formulas must be used. Unfortunately, accuracy of these formulas may be rather low in some cases. There is an obvious need for a simple method that conveniently provides the IMFP values for a studied solid. Such conditions are satisfied by the method that makes it possible to derive the IMFP values from the measured elastic backscattering probability. The present report contains a concise introduction to this method; the main features of such an approach are briefly reviewed and discussed. The method, with some caution, can be applied to any solid, although the conducting or the semiconductor samples are recommended to avoid charging effects. In contrast with the method involving deposition of overlayers, the IMFP values derived from the elastic backscattering intensity are in agreement with the definition supported by American Society for Testing and Materials (ASTM). The measurements can be made using typical electron spectrometers in situ for samples submitted to other studies. Finally, the measurements are nondestructive. The main problem of this method is the complexity of the theoretical model describing multiple electron scattering events in the solid. To facilitate calculations, an extensive user-friendly software packet, EPES has been developed. One of the functions of this packet is to determine, from the Monte Carlo (MC) simulations, the so-called calibration curve, i.e. the dependence of the backscattering probability on the input value of the IMFP. Calculations can be performed for any experimental configuration, and for electron energies ranging from 50 to 10 000 eV. The theoretical model requires knowledge of the total and differential elastic scattering cross sections (DCS). These parameters can be imported from all versions of the NIST Database 64.