Testing the accuracy of low-beam-energy electron-excited X-ray microanalysis with energy-dispersive spectrometry.

The accuracy of electron-excited X-ray microanalysis with energy-dispersive spectrometry (EDS) has been tested in the low beam energy range, specifically at an incident beam energy of 5 keV, which is the lowest beam energy for which a useful characteristic X-ray peak can be excited for all elements of the periodic table, excepting H and He. Elemental analysis results are reported for certified reference materials (CRM), stoichiometric compounds, minerals, and metal alloys of independently known or measured composition which had microscopic homogeneity suitable for microanalysis. Two-hundred sixty-three concentration measurements for 39 elements in 113 materials were determined following the and using the EDS analytical software NIST DTSA-II.

Quantification of Unsupported Thin-Film X-ray Spectra Using Bulk Standards.

A quantification model which uses standard X-ray spectra collected from bulk materials to determine the composition and mass thickness of single-layer and multilayer unsupported thin films is presented. The multivariate model can be iteratively solved for single layers in which each element produces at least one visible characteristic X-ray line. The model can be extended to multilayer thin films in which each element is associated with only one layer.

Registering Particle Data Sets Using a Rotation and Translation Invariant Nearest-Neighbor Algorithm.

It can be useful to register (or align) two sets of particle data measured from the same physical sample. However, if the two data sets were collected at different translational or rotational offsets, finding the optimal registration can be a challenge. We will present an algorithm that efficiently determines the rotation and translational offset that best registers (in a least-squares sense) the corresponding particles in two or more data sets measured from the same sample.

Simulating electron-excited energy dispersive X-ray spectra with the NIST DTSA-II open-source software platform.

NIST DTSA-II is a free, open access, and fully-documented comprehensive software platform for electron-excited X-ray microanalysis with energy dispersive spectrometry (EDS), including tools for quantification, measurement optimization, and spectrum simulation. EDS simulation utilizes a Monte Carlo electron trajectory simulation that includes characteristic and continuum X-ray generation, self-absorption, EDS window absorption, and energy-to-charge conversion leading to peak broadening. Spectra are simulated on an absolute basis considering electron dose and spectrometer parameters.

Energy-Dispersive X-Ray Spectrum Simulation with NIST DTSA-II: Comparing Simulated and Measured Electron-Excited Spectra.

Electron-excited X-ray microanalysis with energy-dispersive spectrometry (EDS) proceeds through the application of the software that extracts characteristic X-ray intensities and performs corrections for the physics of electron and X-ray interactions with matter to achieve quantitative elemental analysis. NIST DTSA-II is an open-access, fully documented, and freely available comprehensive software platform for EDS quantification, measurement optimization, and spectrum simulation. Spectrum simulation with DTSA-II enables the prediction of the EDS spectrum from any target composition for a specified electron dose and for the solid angle and window parameters of the EDS spectrometer.

Reproducible Spectrum and Hyperspectrum Data Analysis Using NeXL.

NeXL is a collection of Julia language packages (libraries) for X-ray microanalysis data processing. NeXLCore provides basic atomic and X-ray physics data and models including support for microanalysis-related data types for materials and k-ratios. NeXLMatrixCorrection provides algorithms for matrix correction and iteration.

Acceptance Testing Methodology for the Production of Standard Reference Material 2806: Medium Test Dust in Hydraulic Fluid.

Standard Reference Material (SRM) 2806: Medium Test Dust in Hydraulic Fluid represents a series of reference materials certified by the National Institute of Standards and Technology (NIST) used to calibrate liquid-borne optical (or automatic) particle counters applied in a wide range of industrial, aerospace, and military applications. The series, including SRM 2806b, and SRM 2806d, was manufactured for NIST by IFTS, Institut de la Filtration et des Techniques Séparatives International Filter Testing Services, in France. An important factor for the acceptance of the material for certification was the degree of bottle-to-bottle homogeneity, which was evaluated by both IFTS and NIST.

Quantitative Electron-Excited X-ray Microanalysis With Low-Energy L-shell X-ray Peaks Measured With Energy-Dispersive Spectrometry.

Quantification of electron-exited X-ray spectra following the standards-based “k-ratio” (unknown/standard intensity) protocol with corrections for “matrix effects” (electron energy loss and backscattering, X-ray absorption, and secondary X-ray fluorescence) is a well-established method with a record of rigorous testing and extensive experience. Two recent studies by Gopon et al. working in the Fe–Si system and Llovet et al.

Embracing Uncertainty: Modeling Uncertainty in EPMA-Part II.

This, the second in a series of articles present a new framework for considering the computation of uncertainty in electron excited X-ray microanalysis measurements, will discuss matrix correction. The framework presented in the first article will be applied to the matrix correction model called "Pouchou and Pichoir's Simplified Model" or simply "XPP." This uncertainty calculation will consider the influence of beam energy, take-off angle, mass absorption coefficient, surface roughness, and other parameters.

Embracing Uncertainty: Modeling the Standard Uncertainty in Electron Probe Microanalysis-Part I.

This is the first in a series of articles which present a new framework for computing the standard uncertainty in electron excited X-ray microanalysis measurements. This article will discuss the framework and apply it to a handful of simple, but useful, subcomponents of the larger problem. Subsequent articles will handle more complex aspects of the measurement model.

Electron-Excited X-ray Microanalysis by Energy Dispersive Spectrometry at 50: Analytical Accuracy, Precision, Trace Sensitivity, and Quantitative Compositional Mapping.

2018 marked the 50th anniversary of the introduction of energy dispersive X-ray spectrometry (EDS) with semiconductor detectors to electron-excited X-ray microanalysis. Initially useful for qualitative analysis, EDS has developed into a fully quantitative analytical tool that can match wavelength dispersive spectrometry for accuracy in the determination of major (mass concentration C > 0.1) and minor (0.

An Iterative Qualitative-Quantitative Sequential Analysis Strategy for Electron-Excited X-ray Microanalysis with Energy Dispersive Spectrometry: Finding the Unexpected Needles in the Peak Overlap Haystack.

When analyzing an unknown by electron-excited energy dispersive X-ray spectrometry, with the entire periodic table possibly in play, how does the analyst discover minor and trace constituents when their peaks are overwhelmed by the intensity of an interfering peak(s) from a major constituent? In this paper, we advocate for and demonstrate an iterative analytical approach, alternating qualitative analysis (peak identification) and standards-based quantitative analysis with peak fitting. This method employs two "tools": (1) monitoring of the "raw analytical total," which is the sum of all measured constituents as well as any such as oxygen calculated by the method of assumed stoichiometry, and (2) careful inspection of the "peak fitting residual spectrum" that is constructed as part of the quantitative analysis procedure in the software engine DTSA-II (a pseudo-acronym) from the National Institute of Standards and Technology. Elements newly recognized after each round are incorporated into the next round of quantitative analysis until the limits of detection are reached, as defined by the total spectrum counts.

Efficient Simulation of Secondary Fluorescence Via NIST DTSA-II Monte Carlo.

Secondary fluorescence, the final term in the familiar matrix correction triumvirate Z·A·F, is the most challenging for Monte Carlo models to simulate. In fact, only two implementations of Monte Carlo models commonly used to simulate electron probe X-ray spectra can calculate secondary fluorescence-PENEPMA and NIST DTSA-II a (DTSA-II is discussed herein). These two models share many physical models but there are some important differences in the way each implements X-ray emission including secondary fluorescence.

Overcoming Peak Overlaps in Titanium- and Vanadium-Bearing Materials with Multiple Linear Least Squares Fitting.

The evolution of the energy dispersive spectrometer (EDS) from the lithium-drifted silicon detector [Si(Li)] to the silicon drift detector (SDD) has created new opportunities in the field of electron probe X-ray microanalysis. The SDD permits operation at significantly higher count rates than the Si(Li) and also provides a more stable energy scale. X-ray spectra captured by EDS can now be analyzed qualitatively or quantitatively under the same beam conditions as used for wavelength dispersive spectrometry (WDS).

Certification of New Standard Reference Material 2806b Medium Test Dust in Hydraulic Fluid.

A new material has been certified to become Standard Reference Material (SRM) 2806b - Medium Test Dust in Hydraulic Fluid. SRM 2806b consists of trace polydisperse, irregularly shaped mineral dust particles suspended in hydraulic fluid. The certified values of SRM 2806b are the projected area circular-equivalent diameters of the collected dust particles from the hydraulic fluid.

Electron-Excited X-Ray Microanalysis at Low Beam Energy: Almost Always an Adventure!

Scanning electron microscopy with energy-dispersive spectrometry has been applied to the analysis of various materials at low-incident beam energies, E 0≤5 keV, using peak fitting and following the measured standards/matrix corrections protocol embedded in the National Institute of Standards and Technology Desktop Spectrum Analyzer-II analytical software engine. Low beam energy analysis provides improved spatial resolution laterally and in-depth. The lower beam energy restricts the atomic shells that can be ionized, reducing the number of X-ray peak families available to the analyst.

Measurement of Trace Constituents by Electron-Excited X-Ray Microanalysis with Energy-Dispersive Spectrometry.

Electron-excited X-ray microanalysis performed with scanning electron microscopy and energy-dispersive spectrometry (EDS) has been used to measure trace elemental constituents of complex multielement materials, where "trace" refers to constituents present at concentrations below 0.01 (mass fraction). High count spectra measured with silicon drift detector EDS were quantified using the standards/matrix correction protocol embedded in the NIST DTSA-II software engine.

Quantitative Electron-Excited X-Ray Microanalysis of Borides, Carbides, Nitrides, Oxides, and Fluorides with Scanning Electron Microscopy/Silicon Drift Detector Energy-Dispersive Spectrometry (SEM/SDD-EDS) and NIST DTSA-II.

A scanning electron microscope with a silicon drift detector energy-dispersive X-ray spectrometer (SEM/SDD-EDS) was used to analyze materials containing the low atomic number elements B, C, N, O, and F achieving a high degree of accuracy. Nearly all results fell well within an uncertainty envelope of ±5% relative (where relative uncertainty (%)=[(measured-ideal)/ideal]×100%). Quantification was performed with the standards-based "k-ratio" method with matrix corrections calculated based on the Pouchou and Pichoir expression for the ionization depth distribution function, as implemented in the NIST DTSA-II EDS software platform.

Performing elemental microanalysis with high accuracy and high precision by scanning electron microscopy/silicon drift detector energy-dispersive X-ray spectrometry (SEM/SDD-EDS).

Electron-excited X-ray microanalysis performed in the scanning electron microscope with energy-dispersive X-ray spectrometry (EDS) is a core technique for characterization of the microstructure of materials. The recent advances in EDS performance with the silicon drift detector (SDD) enable accuracy and precision equivalent to that of the high spectral resolution wavelength-dispersive spectrometer employed on the electron probe microanalyzer platform. SDD-EDS throughput, resolution, and stability provide practical operating conditions for measurement of high-count spectra that form the basis for peak fitting procedures that recover the characteristic peak intensities even for elemental combination where severe peak overlaps occur, such PbS, MoS, BaTiO, SrWO, and WSi.

Diluvian Clustering: A Fast, Effective Algorithm for Clustering Compositional and Other Data.

Diluvian Clustering is an unsupervised grid-based clustering algorithm well suited to interpreting large sets of noisy compositional data. The algorithm is notable for its ability to identify clusters that are either compact or diffuse and clusters that have either a large number or a small number of members. Diluvian Clustering is fundamentally different from most algorithms previously applied to cluster compositional data in that its implementation does not depend upon a metric.

Use of force-sensing array films to improve surface wipe sampling.

Surface wipe sampling, as performed by human operators, is widely used in environmental monitoring and currently subject to a high degree of variability. Two factors relating to sampling efficiency, applied force and area coverage, have not previously been amenable to measurement during wipe sampling. A force-sensing resistor (FSR) array film is used for the first time in this study to measure these factors and provide feedback for operator training, with the goal of reducing inter-operator variability.

Uncertainty estimates for electron probe X-ray microanalysis measurements.

It has been over 60 years since Castaing (Castaing, R. Application of Electron Probes to Local Chemical and Crystallographic Analysis. Ph.

Is scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) quantitative?

Scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) is a widely applied elemental microanalysis method capable of identifying and quantifying all elements in the periodic table except H, He, and Li. By following the "k-ratio" (unknown/standard) measurement protocol development for electron-excited wavelength dispersive spectrometry (WDS), SEM/EDS can achieve accuracy and precision equivalent to WDS and at substantially lower electron dose, even when severe X-ray peak overlaps occur, provided sufficient counts are recorded. Achieving this level of performance is now much more practical with the advent of the high-throughput silicon drift detector energy dispersive X-ray spectrometer (SDD-EDS).

EDS measurements of X-ray intensity at WDS precision and accuracy using a silicon drift detector.

The accuracy and precision of X-ray intensity measurements with a silicon drift detector (SDD) are compared with the same measurements performed on a wavelength dispersive spectrometer (WDS) for a variety of elements in a variety of materials. In cases of major (>0.10 mass fraction) and minor (>0.

Compton scattering artifacts in electron excited X-ray spectra measured with a silicon drift detector.

Artifacts are the nemesis of trace element analysis in electron-excited energy dispersive X-ray spectrometry. Peaks that result from nonideal behavior in the detector or sample can fool even an experienced microanalyst into believing that they have trace amounts of an element that is not present. Many artifacts, such as the Si escape peak, absorption edges, and coincidence peaks, can be traced to the detector.