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Development of a New Quantitative X-Ray Microanalysis Method for Electron Microscopy

Published online by Cambridge University Press:  20 October 2010

Paula Horny*
Affiliation:
Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montréal, Québec H3A 2B2, Canada Département de Génie des Mines, de la Métallurgie et des Matériaux, Université Laval, Québec G1K 7P4, Canada
Eric Lifshin
Affiliation:
College of Nanoscale Science and Engineering, University at Albany—State University of New York, 251 Fuller Road, Albany, NY 12203, USA
Helen Campbell
Affiliation:
Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montréal, Québec H3A 2B2, Canada
Raynald Gauvin
Affiliation:
Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montréal, Québec H3A 2B2, Canada
*
Corresponding author. E-mail: paula.horny@mail.mcgill.ca

Abstract

Quantitative X-ray microanalysis of thick samples is usually performed by measuring the characteristic X-ray intensities of each element in a sample and in corresponding standards. The ratio of the measured intensities from the unknown material to that from the standard is related to the concentration using the ZAF or ϕ(ρz) equations. Under optimal conditions, accuracies approaching 1% are possible. However, all the experimental conditions must remain the same during the sample and standard measurements. This is not possible with cold field emission scanning electron microscopes (FE-SEMs) where beam current can fluctuate around 5% in its stable regime. Very little work has been done on variable beam current conditions (Griffin, B.J. & Nockolds, C.E., Scanning13, 307–312, 1991), and none relating to cold FE-SEM applications. To address this issue, a new method was developed using a single spectral measurement. It is similar in approach to the Cliff-Lorimer method developed for the analytical transmission electron microscope. However, corrections are made for X rays generated from thick specimens using the ratio of the characteristic X-ray intensities of two elements in the same material. The proposed method utilizes the ratio of the intensity of a characteristic X-ray normalized by the sum of X-ray intensities of all the elements measured for the sample, which should also reduce the amplitude of error propagation. Uncertainties in the physical parameters of X-ray generation are corrected using a calibration factor that must be previously acquired or calculated. As an example, when this method was applied to the calculation of the composition of Au-Cu National Institute of Standards and Technology standards measured with a cold field emission source SEM, relative accuracies better than 5% were obtained.

Type
Instrumentation and Software Developments
Copyright
Copyright © Microscopy Society of America 2010

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References

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