Electron microprobe-based quantitative compositional measurement of first-row transition metals using their L$\alpha$ X-ray lines is hampered by, among other effects, self-absorption. This effect, which occurs when a broad X-ray line is located close to a broad absorption edge, is not accounted for by matrix corrections. To assess the error due to neglecting self-absorption, we calculate the L$\alpha$ X-ray intensity emitted from metallic Fe, Ni, Cu, and Zn targets, assuming a Lorentzian profile for the X-ray line and taking into account the energy dependence of the mass absorption coefficient near the absorption edge. We find that calculated X-ray intensities depart increasingly, for increasing electron beam energy, from those obtained assuming a narrow X-ray line and a single fixed absorption coefficient (conventional approach), with a maximum deviation of $\sim$15% for Ni and of $\sim$10% for Fe. In contrast, X-ray intensities calculated for metallic Zn and Cu do not differ significantly from those obtained using the conventional approach. The implications of these results for the analysis of transition-metal compounds by electron probe microanalysis as well as strategies to account for self-absorption effects are discussed.

Electron probe microanalysis is a nondestructive technique widely used to determine the elemental composition of bulk samples. This was extended to layered specimens, with the development of appropriate software. The traditional quantification method requires the use of matrix correction procedures based upon models of the ionization depth distribution, the so-called ϕ(ρz) distribution. Most of these models have led to commercial quantification programs but only few of them allow the quantification of layered specimens. Therefore, we developed BadgerFilm, a free open-source thin film program available to the general public. This program implements a documented ϕ(ρz) model as well as algorithms to calculate fluorescence in bulk and thin film samples. Part 1 of the present work aims at describing the operation of the implemented ϕ(ρz) distribution model and validating its implementation against experimental measurements and Monte Carlo simulations on bulk samples. The program has the ability to predict absolute X-ray intensities that can be directly compared to Monte Carlo simulations. We demonstrate that the implemented model works very well for bulk materials. And as will be shown in Part 2, BadgerFilm predictions for thin film specimens are also shown to be in good agreements with experimental and Monte Carlo results.

Since the 1960s, thicknesses and compositions of thin-film specimens have been determined by using the nondestructive technique of electron probe microanalysis. This approach, refined in the 1990s, is based upon models of the ionization depth distribution, the so-called ϕ(ρz) distribution, and is capable of analyzing layered specimens. Most of these quantification models have led to commercial programs. However, these programs may have possible limitations: some may not be directly compatible with modern computers, they often are “black boxes” making it difficult to assess the reliability of the results, and they are sometimes expensive enough to restrain many labs from purchasing them. We present a user-friendly, free, open-source program, BadgerFilm, implementing a documented ϕ(ρz) model and algorithms allowing the quantification of stratified samples. The program has the ability to calculate absolute X-ray intensities that can be directly compared with Monte Carlo simulations. We give a detailed explanation for the operation of the employed ϕ(ρz) model in thin films. A wide range of detailed Monte Carlo simulations and experimental data have been used to evaluate and validate the accuracy of the implemented algorithms. BadgerFilm demonstrated excellent quantification results for the films and in many cases for the substrates.

The recent availability of Schottky-type field emission electron microprobes provides incentive to consider analyzing micrometer-sized features. Yet, to quantify sub-micrometer-sized features, the electron interaction volume must be reduced by decreasing accelerating voltage. However, the K lines of the transition elements (e.g., Fe) then cannot be excited, and the L lines must be used. The Fe Lα1,2 line is the most intense of the L series but bonding effects change its atomic parameters because it involves a valence band electron transition. For successful traditional electron probe microanalysis, the mass absorption coefficient (MAC) must be accurately known, but the MAC of Fe Lα1,2 radiation by Fe atoms varies from one Fe-compound to another and is not well known. We show that the conventional method of measuring the MAC by an electron probe cannot be used in close proximity to absorption edges, making its accurate determination impossible. Fortunately, we demonstrate, using a set of Fe–silicide compounds, that it is possible to derive an accurate calibration curve, for a given accelerating voltage and takeoff angle, which can be used to quantify Fe in Fe–silicide compounds. The calibration curve can be applied to any spectrometer without calibration and gives accurate quantification results.