Dale E. Newbury

National Institute of Standards and Technology, Maryland, United States

Are you Dale E. Newbury?

Claim your profile

Publications (126)191.34 Total impact

  • Dale E. Newbury, Nicholas W. M. Ritchie
    [Show abstract] [Hide abstract]
    ABSTRACT: Elemental mapping at the microstructural level by scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS), while widely applied in science, engineering, and technology, has been limited in performance by the throughput of the lithium-drifted silicon detector [Si(Li)-EDS] which restricts the number of X-ray counts measured per image pixel. The emergence of the silicon drift detector (SDD-EDS) has greatly extended the X-ray throughput, by a factor of 25 to 70 for the same spectral resolution. This improved performance enables practical X-ray spectrum imaging (XSI), in which a complete X-ray spectrum is recorded at each image pixel. By performing complete quantitative corrections for background, peak overlap, and matrix effects to each pixel spectrum, full compositional mapping can be achieved. Various elemental mapping collection strategies are described, including quantitative mapping at the major (concentration C > 0.1 mass fraction), minor (0.01 ≤ C ≤ 0.1), and trace (C < 0.01) constituent levels, extreme pixel density (gigapixel) mapping, rapid mapping (in 10 seconds or less), and high spatial resolution mapping with the thermal field emission gun scanning electron microscope.
    Journal of Analytical Atomic Spectrometry 06/2013; 28(7):973-988. · 3.16 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: It has been over 60 years since Castaing introduced the technique of electron probe x-ray microanalysis (EPMA) yet the community remains unable to quantify some of the largest terms in the technique's uncertainty budget. Historically, the EPMA community has assigned uncertainties to its measurements which reflect the measurement precision portion of the uncertainty budget and omitted terms related to the measurement accuracy. Yet, in many cases, the precision represents only a small fraction of the total budget. This paper addresses the shortcoming by considering two significant sources of uncertainty in the quantitative matrix correction models - the mass absorption coefficient, [μ⁄ρ], and the backscatter coefficient, η. Understanding the influence of these sources provides insight into the utility of EPMA measurements and, equally important, it allows practitioners to develop strategies to optimize measurement accuracy by minimizing the influence of poorly known model parameters.
    Analytical Chemistry 10/2012; · 5.70 Impact Factor
  • Dale E Newbury, Nicholas W M Ritchie
    [Show abstract] [Hide abstract]
    ABSTRACT: 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). However, three measurement issues continue to diminish the impact of SEM/EDS: (1) In the qualitative analysis (i.e., element identification) that must precede quantitative analysis, at least some current and many legacy software systems are vulnerable to occasional misidentification of major constituent peaks, with the frequency of misidentifications rising significantly for minor and trace constituents. (2) The use of standardless analysis, which is subject to much broader systematic errors, leads to quantitative results that, while useful, do not have sufficient accuracy to solve critical problems, e.g. determining the formula of a compound. (3) EDS spectrometers have such a large volume of acceptance that apparently credible spectra can be obtained from specimens with complex topography that introduce uncontrolled geometric factors that modify X-ray generation and propagation, resulting in very large systematic errors, often a factor of ten or more. SCANNING 00: 1-28, 2012. Published 2012 Wiley Periodicals, Inc.†
    Scanning 08/2012; · 1.29 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 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 (>0.01 mass fraction) elements, the SDD is demonstrated to perform as well or better than the WDS. This is demonstrated both for simple cases in which the spectral peaks do not interfere (SRM-481, SRM-482, and SRM-479a), and for more difficult cases in which the spectral peaks have significant interferences (the Ba L/Ti K lines in a series of Ba/Ti glasses and minerals). We demonstrate that even in the case of significant interference high count SDD spectra are capable of accurately measuring Ti in glasses with Ba:Ti mass fraction ratios from 2.7:1 to 23.8:1. The results suggest that for many measurements wavelength spectrometry can be replaced with an SDD with improved accuracy and precision.
    Microscopy and Microanalysis 07/2012; 18(4):892-904. · 2.50 Impact Factor
  • Dale E. Newbury, Nicholas W. M. Ritchie
    [Show abstract] [Hide abstract]
    ABSTRACT: Scanning electron microscopy with energy dispersive x-ray spectrometry (SEM/EDS) is a powerful and flexible elemental analysis method that can identify and quantify elements with atomic numbers > 4 (Be) present as major constituents (where the concentration C > 0.1 mass fraction, or 10 weight percent), minor (0.01<= C <= 0.1) and trace (C < 0.01, with a minimum detectable limit of ~+/- 0.0005 - 0.001 under routine measurement conditions, a level which is analyte and matrix dependent ). SEM/EDS can select specimen volumes with linear dimensions from ~ 500 nm to 5 μm depending on composition (masses ranging from ~ 10 pg to 100 pg) and can provide compositional maps that depict lateral elemental distributions. Despite the maturity of SEM/EDS, which has a history of more than 40 years, and the sophistication of modern analytical software, the method is vulnerable to serious shortcomings that can lead to incorrect elemental identifications and quantification errors that significantly exceed reasonable expectations. This paper will describe shortcomings in peak identification procedures, limitations on the accuracy of quantitative analysis due to specimen topography or failures in physical models for matrix corrections, and quantitative artifacts encountered in xray elemental mapping. Effective solutions to these problems are based on understanding the causes and then establishing appropriate measurement science protocols. NIST DTSA II and Lispix are open source analytical software available free at www.nist.gov that can aid the analyst in overcoming significant limitations to SEM/EDS.
    Proc SPIE 05/2012;
  • [Show abstract] [Hide abstract]
    ABSTRACT: 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. Others, such as secondary fluorescence peaks and scatter peaks, can be traced to the sample. We have identified a new sample-dependent artifact that we attribute to Compton scattering of energetic X-rays generated in a small feature and subsequently scattered from a low atomic number matrix. It seems likely that this artifact has not previously been reported because it only occurs under specific conditions and represents a relatively small signal. However, with the advent of silicon drift detectors and their utility for trace element analysis, we anticipate that more people will observe it and possibly misidentify it. Though small, the artifact is not inconsequential. Under some conditions, it is possible to mistakenly identify the Compton scatter artifact as approximately 1% of an element that is not present.
    Microscopy and Microanalysis 11/2011; 17(6):903-10. · 2.50 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: X-ray area scanning (“dot mapping”) is a technique widely used in electron probe microanalysis for determining the spatial distribution of elemental constituents. Although powerful, this technique is subject to significant limitations on concentration sensitivity and flexibility for subsequent processing. The new technique of compositional mapping overcomes these limitations. In compositional mapping, a complete quantitative electron probe analysis is carried out at each point of a matrix scan. The resulting matrices of concentration values can be assembled into images in a digital image processor by assigning gray or color intensities to the actual concentrations rather than the raw spectral intensities. Digital compositional maps can be readily manipulated by a wide variety of image processing techniques to improve the visibility of features of interest.
    Scanning 08/2011; 10(6):213 - 225. · 1.29 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Samples of aluminium-lithium alloys have been observed by scanning ion microscopy and analysed by secondary ion mass spectrometry. The high signal-to-noise ratio of the positive secondary lithium ion opens up the possibility of both high resolution imaging and microanalysis of lithium distributions in aluminium and other materials. Some of the problems encountered due to sample preparation are discussed and ion images of both the artefacts and the true lithium distribution are shown.
    Journal of Microscopy 08/2011; 148(3):241 - 252. · 1.63 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: SUMMARYA new, simplified procedure for correcting the defocusing observed in low-magnification digital maps obtained with the electron microprobe using wavelength spectrometers is described. This procedure uses a wavelength scan of the analysed element and the geometric relationship between the specimen and the diffracting crystal to calculate a model of a standard map, which is subsequently used in the quantification of each pixel of the unknown map. The results of this new procedure are compared with the earlier method of using an experimentally obtained standard map.
    Journal of Microscopy 08/2011; 155(2):183 - 198. · 1.63 Impact Factor
  • Dale E Newbury, Nicholas W M Ritchie
    [Show abstract] [Hide abstract]
    ABSTRACT: The high throughput of the silicon drift detector energy dispersive X-ray spectrometer (SDD-EDS) enables X-ray spectrum imaging (XSI) in the scanning electron microscope to be performed in frame times of 10-100 s, the typical time needed to record a high-quality backscattered electron (BSE) image. These short-duration XSIs can reveal all elements, except H, He, and Li, present as major constituents, defined as 0.1 mass fraction (10 wt%) or higher, as well as minor constituents in the range 0.01-0.1 mass fraction, depending on the particular composition and possible interferences. Although BSEs have a greater abundance by a factor of 100 compared with characteristic X-rays, the strong compositional contrast in element-specific X-ray maps enables XSI mapping to compete with BSE imaging to reveal compositional features. Differences in the fraction of the interaction volume sampled by the BSE and X-ray signals lead to more delocalization of the X-ray signal at abrupt compositional boundaries, resulting in poorer spatial resolution. Improved resolution in X-ray elemental maps occurs for the case of a small feature composed of intermediate to high atomic number elements embedded in a matrix of lower atomic number elements. XSI imaging strongly complements BSE imaging, and the SDD-EDS technology enables an efficient combined BSE-XSI measurement strategy that maximizes the compositional information. If 10 s or more are available for the measurement of an area of interest, the analyst should always record the combined BSE-XSI information to gain the advantages of both measures of compositional contrast.
    Scanning 06/2011; 33(3):174-92. · 1.29 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: X-ray elemental mapping and X-ray spectrum imaging are powerful microanalytical tools. However, their scope is often limited spatially by the raster area of a scanning electron microscope or microprobe. Limited sampling size becomes a significant issue when large area (>10 cm²), heterogeneous materials such as concrete samples or others must be examined. In such specimens, macro-scale structures, inclusions, and concentration gradients are often of interest, yet microbeam methods are insufficient or at least inefficient for analyzing them. Such requirements largely exclude the samples of interest presented in this article from electron probe microanalysis. Micro X-ray fluorescence-X-ray spectrum imaging (μXRF-XSI) provides a solution to the problem of macro-scale X-ray imaging through an X-ray excitation source, which can be used to analyze a variety of large specimens without many of the limitations found in electron-excitation sources. Using a mid-sized beam coupled with an X-ray excitation source has a number of advantages, such as the ability to work at atmospheric pressure and lower limits of detection owing to the absence of electron-induced bremsstrahlung. μXRF-XSI also acts as a complement, where applicable, to electron microbeam X-ray output, highlighting areas of interest for follow-up microanalysis at a finer length scale.
    Microscopy and Microanalysis 06/2011; 17(3):410-7. · 2.50 Impact Factor
  • Article: Editorial.
    Dale E Newbury, Brendan Griffin
    Scanning 05/2011; · 1.29 Impact Factor
  • Dale E. Newbury, Nicholas W. M. Ritchie
    [Show abstract] [Hide abstract]
    ABSTRACT: The extraordinary throughput of the silicon drift detector energy dispersive x-ray spectrometer (SDD-EDS) enables collection of EDS spectra with much higher integrated counts within practical time periods, e.g., 100 s or less, compared to past experience with the Si(Li)-EDS. Such high count SDD spectra, containing one million to ten million counts, yield characteristic peak intensities with relative standard deviation below 0.25%, a precision similar to that achieved with wavelength dispersive spectrometry (WDS), the "gold standard" of microprobe analysis, but at lower dose because of the greater solid angle of the SDD-EDS. Such high count SDD-EDS spectra also enable more accurate quantification, nearly indistinguishable from WDS for major and minor constituents when the WDS unknown-to-standard intensity ratio ("k-value") protocol is followed. A critical requirement to satisfy this measurement protocol is that the specimen must be a highly polished bulk target. The geometric character of specimens examined in the scanning electron microscope (SEM) often deviates greatly from the ideal flat bulk target but EDS spectra can still be readily obtained and analyzed. The influence of geometric factors such as local inclination and surface topography on the accuracy of quantitative EDS analysis is examined. Normalized concentration values are subject to very large errors, as high as a factor of 10, as a result of deviation of the specimen geometry from the ideal flat bulk target.
    Proc SPIE 05/2011;
  • Proc SPIE 04/2011; 8036.
  • D. Newbury, N. Ritchie
    Microscopy and Microanalysis 01/2011; 17:558-559. · 2.50 Impact Factor
  • D. Newbury, N. Ritchie
    Microscopy and Microanalysis 01/2011; 17:884-885. · 2.50 Impact Factor
  • A. Lindstrom, N. Ritchie, D. Newbury
    Microscopy and Microanalysis 01/2011; 17:1854-1855. · 2.50 Impact Factor
  • N. Ritchie, J. Davis, D. Newbury
    Microscopy and Microanalysis 01/2011; 17:556-557. · 2.50 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: It is well known that the chemical composition of a substance can influence the instrumental mass bias in secondary ion mass spectrometry (SIMS) [1][2] and the matrix chemistry influences relative sensitivity factors for many compounds [3][4]. When samples are smaller than the primary beam size, the chemistry of the substrate, and the matrix of the sample, influence the secondary ion yields. There are numerous applications where this can occur. Even the relative production of simple molecular species can be influenced by the substrate chemistry by preferential binding to the atoms from the region above the sample making the desired simple molecular ion less likely to occur. We have performed a study of the influence of substrate material on sensitivity factors. Substrates of C, Si, and Au, were used for measurements of Th, and U ions and their oxide and dioxide ions. Oxygen backfilling was also used for some measurements (see Figure 1). Correlations exist, in the case where oxygen backfilling was not used, with the dissociation energies of the substrate element oxides and the element oxide ions from the particles. This correlation can be observed in Figure 2. A complete set of data thus far collected will be presented. References [1] EH Hauri,, AM Shaw, JH Wang, JE Dixon, PL King, C Mandeville, ``Chem. Geo.'', 235, (2006) pp. 352-365 [2] IC Lyon, JM Saxton, G Turner, R Hinton, ``Rapid Comm. in Mass Spec.'', 8 (10), (1994), pp. 837-843 [3] RG Wilson, FA Stevie, and CW Magee Secondary-ion mass spec. Wiley-interscience, New York (1989). ISBN No.: 0 471 51945 6 [4] AJ Fahey, ``Mass Spec. and Ion Proc.'', 176, (1998), pp. 63-76 Figure 1: Oxide signals with O-flooding on 3 different substrates. Figure 2: Oxide signals without O-flooding on 3 different substrates.
    AGU Fall Meeting Abstracts. 12/2010;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: On the morning of July 16, 1945, the first atomic bomb was exploded in New Mexico on the White Sands Proving Ground. The device was a plutonium implosion device similar to the device that destroyed Nagasaki, Japan, on August 9 of that same year. Recently, with the enactment of US public law 111-140, the "Nuclear Forensics and Attribution Act," scientists in the government and academia have been able, in earnest, to consider what type of forensic-style information may be obtained after a nuclear detonation. To conduct a robust attribution process for an exploded device placed by a nonstate actor, forensic analysis must yield information about not only the nuclear material in the device but about other materials that went into its construction. We have performed an investigation of glassed ground debris from the first nuclear test showing correlations among multiple analytical techniques. Surprisingly, there is strong evidence, obtainable only through microanalysis, that secondary materials used in the device can be identified and positively associated with the nuclear material.
    Proceedings of the National Academy of Sciences 11/2010; 107(47):20207-12. · 9.74 Impact Factor

Publication Stats

517 Citations
191.34 Total Impact Points

Institutions

  • 1991–2013
    • National Institute of Standards and Technology
      • Analytical Chemistry Division
      Maryland, United States
  • 2007
    • Oak Ridge National Laboratory
      Oak Ridge, Florida, United States
  • 1992–2000
    • Lehigh University
      • Department of Materials Science and Engineering
      Gaithersburg, MD, United States
  • 1993
    • National Institutes of Health
      Maryland, United States
  • 1970
    • University of Oxford
      Oxford, England, United Kingdom