A characteristic fluorescence correction for electron-probe microanalysis of thin coatings

Abstract

An equation is developed for calculating the X-ray fluorescence produced in a coating by characteristic X-rays generated in the substrate material. The correction is applied to experimental microanalysis data obtained for thin coatings deposited on a range of substrate materials and is shown to give satisfactory results. An extension of the method to include multicomponent systems is then described.

Secondary Fluorescence Correction for Characteristic and Bremsstrahlung X-Rays Using Monte Carlo X-ray Depth Distributions Applied to Bulk and Multilayer Materials

“…Thus materials far away from the primary interaction volume can contribute to X-ray emission. Cox et al mentioned that the difference in total intensity resulting from the fluorescence effect can reach 15% (Cox et al, 1979). It is therefore necessary to make corrections for fluorescence effects during quantitative X-ray microanalysis.…”

Secondary fluorescence in electron probe microanalysis of material couples

“…Although the effective electron range is relatively small (of the order of a few µm), characteristic primary x-rays penetrate much deeper into the specimen and can ionize atoms at much larger distances, thus degrading the spatial resolution of the technique as well as the accuracy of evaluated chemical compositions (Reed and Long 1963). Analytical formulae to account for secondary fluorescence corrections in simple geometries have been proposed for homogeneous specimens (Reed 1965), for material couples (Hénoc et al 1969, Maurice et al 1965, Bastin et al 1983, for thin films on substrates (Cox et al 1979) and for multilayers (Youhua et al 1988). Usually, these formulae only account for fluorescence from characteristic x-rays, the contribution from the bremsstrahlung continuum has only been considered for homogeneous samples.…”

Method for the calculation of the chemical composition of a thin film by Monte Carlo simulation and electron probe microanalysis

“…Omission of this effect may constitute a major source of error in procedures and would be particularly serious when the substrate radiation has an energy slightly greater than the critical ionization energy of the element in the thin film. 25 Cox et al gave an example to show that in some samples the enhancement of the x-ray emission due to the contribution of the characteristic fluorescence can amount to 16%. 25 In view of this, the characteristic fluorescence is taken into account in the present method.…”

“…25 Cox et al gave an example to show that in some samples the enhancement of the x-ray emission due to the contribution of the characteristic fluorescence can amount to 16%. 25 In view of this, the characteristic fluorescence is taken into account in the present method. In the Monte Carlo simulation models utilized by Murata and Nakagawa et al, the mean free path of the electron is used as a variable step length.…”

“…The calculation of the characteristic fluorescence is complicated for a stratified sample. The simple equation proposed by Cox et al 25 can be used to calculate the characteristic fluorescence generated in the film by characteristic x-rays emitted only from the substrate, not from elements contained in the identical multicomponent film. The attenuation of these x-rays in traveling to the film is neglected in the equation.…”