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Proceedings Paper

Characterizing heterogeneous particles with SEM/SDD-EDS mapping and NIST Lispix
Author(s): Dale Newbury; Nicholas Ritchie; David Bright
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Paper Abstract

Compositional measurements of microscopic particles by scanning electron microscopy/energy dispersive x-ray spectrometry (SEM/EDS) typically assume particle homogeneity so that a representative EDS spectrum can be collected by continuously bracket scanning the particle (overscanning). Particles are often found to be complex structures comprised of smaller entities that are elementally different, knowledge of which is inevitably lost with particle overscanning. Heterogeneity can be directly visualized with x-ray spectrum image mapping performed in a high resolution thermal field emission gun SEM combined with the silicon drift detector (SDD)-EDS. SDD-EDS is capable of x-ray collection with output count rates in excess of 1 MHz, enabling spectrum image mapping with useful pixel density (128x128 or more), intensity range (8 - 16 bits), and compositional sensitivity (detection to approximately 1 weight percent) with a total time of 3 - 30 s when a high beam current (e.g., 50 nA) is utilized. Spectrum image datacubes can range from 100 Mbyte to several gigabytes. NIST Lispix contains extensive image processing tools to extract spectral and image information from such large datacubes. In addition to particle chemical heterogeneity, spectrum image mapping can directly reveal the effects of geometric factors (size, shape, curvature) that modify x-ray generation and emission from particles and which must be considered in particle quantification calculations.

Paper Details

Date Published: 3 June 2009
PDF: 11 pages
Proc. SPIE 7378, Scanning Microscopy 2009, 73780Q (3 June 2009); doi: 10.1117/12.820874
Show Author Affiliations
Dale Newbury, National Institute of Standards and Technology (United States)
Nicholas Ritchie, National Institute of Standards and Technology (United States)
David Bright, National Institute of Standards and Technology (United States)

Published in SPIE Proceedings Vol. 7378:
Scanning Microscopy 2009
Michael T. Postek; Michael T. Postek; Michael T. Postek; Dale E. Newbury; Dale E. Newbury; Dale E. Newbury; S. Frank Platek; S. Frank Platek; S. Frank Platek; David C. Joy; David C. Joy; David C. Joy, Editor(s)

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