29 May 2013 Scanning electron microscopy/energy dispersive spectrometry fixedbeam or overscan x-ray microanalysis of particles can miss the real structure: x-ray spectrum image mapping reveals the true nature
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Abstract
The typical strategy for analysis of a microscopic particle by scanning electron microscopy/energy dispersive spectrometry x-ray microanalysis (SEM/EDS) is to use a fixed beam placed at the particle center or to continuously overscan to gather an “averaged” x-ray spectrum. While useful, such strategies inevitably concede any possibility of recognizing microstructure within the particle, and such fine scale structure is often critical for understanding the origins, behavior, and fate of particles. Elemental imaging by x-ray mapping has been a mainstay of SEM/EDS analytical practice for many years, but the time penalty associated with mapping with older EDS technology has discouraged its general use and reserved it more for detailed studies that justified the time investment. The emergence of the high throughput, high peak stability silicon drift detector (SDD-EDS) has enabled a more effective particle mapping strategy: “flash” x-ray spectrum image maps can now be recorded in seconds that capture the spatial distribution of major (concentration, C > 0.1 mass fraction) and minor (0.01 ≤ C ≤ 0.1) constituents. New SEM/SDD-EDS instrument configurations feature multiple SDDs that view the specimen from widely spaced azimuthal angles. Multiple, simultaneous measurements from different angles enable x-ray spectrometry and mapping that can minimize the strong geometric effects of particles. The NIST DTSA-II software engine is a powerful aid for quantitatively analyzing EDS spectra measured individually as well as for mapping information (available free for Java platforms at: http://www.cstl.nist.gov/div837/837.02/epq/dtsa2/index.html).
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Dale E. Newbury, Dale E. Newbury, Nicholas W. M. Ritchie, Nicholas W. M. Ritchie, } "Scanning electron microscopy/energy dispersive spectrometry fixedbeam or overscan x-ray microanalysis of particles can miss the real structure: x-ray spectrum image mapping reveals the true nature", Proc. SPIE 8729, Scanning Microscopies 2013: Advanced Microscopy Technologies for Defense, Homeland Security, Forensic, Life, Environmental, and Industrial Sciences, 872902 (29 May 2013); doi: 10.1117/12.2011790; https://doi.org/10.1117/12.2011790
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