Effective attenuation lengths for quantitative determination of surface composition by Auger-electron spectroscopy and X-ray photoelectron spectroscopy

Abstract

The effective attenuation length (EAL) is normally used in place of the inelastic mean free path (IMFP) to account for elastic-scattering effects when describing the attenuation of Auger electrons and photoelectrons from a planar substrate by an overlayer film. An EAL for quantitative determination of surface composition by Auger-electron spectroscopy (AES) or X-ray photoelectron spectroscopy (XPS) is similarly useful to account for elastic-scattering effects on the signal intensities. We calculated these EALs for four elemental solids (Si, Cu, Ag, and Au) and for energies between 160 eV and 1.4 keV. The XPS calculations were made for two instrumental configurations while the AES calculations were made from the XPS formalism after “switching off” the XPS anisotropy. The EALs for quantitative determination of surface composition by AES and XPS were weak functions of emission angle for emission angles between 0 and 50°. The ratios of the average values of these EALs to the corresponding IMFPs could be fitted to a second-order function of the single-scattering albedo, a convenient measure of the strength of elastic-scattering effects. EALs for quantitative determination of surface composition by AES and XPS for other materials can be simply found from this relationship.

Stabilization of Orthorhombic CoSe2 by 2D-rGO/MWCNT Heterostructures for Efficient Hydrogen Evolution Reaction and Flexible Energy Storage Device Applications

“…The high resolution XPS spectra of Co 2p were resolved into two peaks corresponding to Co 2p 3/2 and Co 2p 1/2 . Further, the Co 2p 3/2 peak can be deconvoluted into three chemical components at binding energies of 778.5, 779.9, and 784.5 eV, which were ascribed to the Co–Co, Co–Se, and Co–O (the existence of a thin oxide layer on the surface due to atmospheric exposure) binding structures, as well as the shakeup satellite peak (Figure b). The well fitted binding energies at 778.5 ± 0.2 eV (Co 2p 3/2 ) and 793.8 ± 0.2 eV (Co 2p 1/2 ) corresponded to Co III components, whereas the associated satellite structures at 779.9 ± 0.2 eV (Co 2p 3/2 ), 798.8 ± 0.2 eV (Co 2p 1/2 ) revealed the presence of a Co II constituent.…”

Characterization of Recombinant His-Tag Protein Immobilized onto Functionalized Gold Nanoparticles

“…The attenuation of the XPS substrate signal or the introduction of nitrogen by the adsorption of a protein can be used to calculate the adsorbed film thickness of the surface [36,37,38,39]. The overlayer thickness was calculated by analyzing two samples with the same modification (Au/AuNPs/3MPA/Ni 2+ /(His) 6 -rHbI).…”

Quantification of hard X‐ray photoelectron spectroscopy: Calculating relative sensitivity factors for 1.5‐ to 10‐keV photons in any instrument geometry

“…When elastic scattering must be considered, the change in observed electron intensity may be estimated using the appropriate EALs in place of the inelastic mean free path in Equation 1. The works of Jablonski and Powell [35][36][37][38] provide detailed insight into the effects of elastic scattering on photoelectron intensity, methods for their correction and the various types of EAL that should be used. Care must be taken that the appropriate combinations of terms for elastic and inelastic scattering are used when calculating RSFs to avoid redundancies, that is, if appropriate EALs are used, the term S in Equation 1 is not required and vice versa.…”