Electron differential inverse mean free path for surface electron spectroscopy

Chen, Yung-Fu; Kwei, C. M.

doi:10.1016/0039-6028(96)00616-4

Cited by 81 publications

(79 citation statements)

References 41 publications

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“…Two typical models are usually apply to calculate the DIIMFP, i.e. the semi-classical one 20,28 and quantum mechanical one 29,30 , respectively. In our recent work the semi-classical model is used, partly because it gives, in most cases 31 , very close results with the quantum mechanical model, and partly and more importantly, because it is computationally more efficient than the quantum mechanical one.…”

Section: -21mentioning

confidence: 99%

Absolute determination of optical constants by reflection electron energy loss spectroscopy

Tóth

et al. 2017

Phys. Rev. B

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We present an absolute extraction method of optical constants of metal from the measured reflection electron energy loss (REELS) spectra by using the recently developed reverse Monte Carlo (RMC) technique. The method is based on a direct physical modeling of electron elastic and electron inelastic scattering near the surface region where the surface excitation becomes important to fully describe the spectrum loss feature intensity in relative to the elastic peak intensity. An optimization procedure of oscillator parameters appeared in the energy loss function (ELF) for describing electron inelastic scattering due to the bulk-and surfaceexcitations was performed with the simulated annealing method by a successive comparison between the measured and Monte Carlo simulated REELS spectra. The ELF and corresponding optical constants of Fe were obtained from the REELS spectra measured at incident energies of 1000, 2000 and 3000 eV. The validity of the present optical data has been verified with the f-and ps-sum rules showing the accuracy and applicability of the present approach. Our data are also compared with previous optical data from other sources.There is a continuous interest and effort on the determination of optical constants of solids due to their importance in both fundamental researches and applications. Optical methods based on reflectance and absorption spectroscopy with ellipsometry were extensively employed up to now and the measured data for metals and semiconductors were compiled to form a database of optical constants.1,2 However, many materials still lack the data in the intermediate photon energy range around 20~50 eV. Furthermore, the available data usually consist of different energy regions measured by different groups and means and, a)

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Section: -21mentioning

confidence: 99%

Absolute determination of optical constants by reflection electron energy loss spectroscopy

Tóth

et al. 2017

Phys. Rev. B

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“…The electron inelastic scattering in a surface region can also be described by a dielectric function theory, 8 either in a semiclassical 9 or in a quantum mechanical 10,11 form. In this way, a theory should provide the information of differential inelastic scattering cross section on electron positions because surface excitation can only occur for electrons moving in the surface region and for electrons moving due to the asymmetry of space.…”

Section: Electron-surface Inelastic Interactionmentioning

confidence: 99%

Monte Carlo simulation study of electron interaction with solids and surfaces

Ding

Salma

et al. 2006

Surface & Interface Analysis

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A brief overview is given on several aspects of applications of the Monte Carlo (MC) simulation method to surface-related electron spectroscopy and microscopy. For the MC modeling of electron interaction with solids, the electron inelastic scattering cross section is calculated by the use of bulk dielectric function with optical constants in a dielectric functional approach. This has enabled the systematic reproductions of the experimental energy distributions of backscattered electrons for a number of elemental materials. An improved calculation of backscattering factor for quantitative AES analysis has been performed on the basis of a new definition and by making use of the up-to-date relevant cross sections. The physical reason is given for the backscattering factor that can be less than unity for very low primary energies close to the ionization energy and/or for large incident angles. For the MC modeling of electron interaction with surfaces, the inelastic scattering of electrons moving in a surface region is treated in a self-energy formalism. The model has enabled the evaluation of the surface excitation effect through the calculation of position-dependent electron IMFP. A simulation of REELS spectra for Ag is compared with an experiment; a reasonable agreement found on the surface plasmon peak intensity normalized with elastic peak intensity thus verifies this modeling of electron interaction with surfaces. Finally, the MC simulation code has been extended to deal with complex sample geometries. By using basic building blocks to construct a complex geometry and the ray-tracing technique for correction of electron flight-step-length sampling, the structured and/or inhomogeneous sample can be modeled with reasonable flexibility.

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“…Vicanek [11] investigated electron energy loss while they move parallel to the solid surface in order to determine the stopping power as a function of the distance from the surface. Chen and Kwei [12] derived a semiclassical expression for the position-dependent DIIMFP and included the depth dependence of surface excitation probability (SEP); they found that the surface excitation by electrons is extended on both sides of the vacuum-solid interface. Ding [4,7,13] employed a self-energy formalism to study the surface excitation effect on a free-electron material surface and real metal surfaces and obtained the positiondependent DIIMFP in the near-surface region.…”

Section: Introductionmentioning

confidence: 99%

Optical properties of silver thin films, derived from REELS

Zhang

Chen

Ding

et al. 2010

Surface & Interface Analysis

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The differential surface excitation probabilities (DSEPs) for medium-energy electrons traveling in Ag are extracted from reflection electron energy loss spectroscopy (REELS) spectra by using the Werner's elimination-retrieved algorithm. Based on a surface Kramers-Kronig dispersion relationship, the electronic structure and optical properties of Ag thin film are determined. The results show that the optical property curves between surface thin layer and bulk are similar in shape, whereas they deviate quantitatively for energies below 40 eV, which may be caused by the different electronic structures at surface and in bulk. The present data would be an appropriate approximation to the optical properties of thin film, whose thickness is characterized by the inelastic mean free path of the electrons in a REELS experiment.

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Electron differential inverse mean free path for surface electron spectroscopy

Cited by 81 publications

References 41 publications

Absolute determination of optical constants by reflection electron energy loss spectroscopy

Absolute determination of optical constants by reflection electron energy loss spectroscopy

Monte Carlo simulation study of electron interaction with solids and surfaces

Optical properties of silver thin films, derived from REELS

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