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Electron Beam-Induced Carbon Erosion and the Impact on Electron Probe Microanalysis

Published online by Cambridge University Press:  16 November 2018

Mike B. Matthews ,
Stuart L. Kearns  and
Ben Buse
Mike B. Matthews*
Affiliation:
AWE, Aldermaston, Reading, RG7 4PR, UK University of Bristol, School of Earth Sciences, Wills Memorial Building, Queens Road, Clifton, BS8 1RJ, UK
Stuart L. Kearns
Affiliation:
University of Bristol, School of Earth Sciences, Wills Memorial Building, Queens Road, Clifton, BS8 1RJ, UK
Ben Buse
Affiliation:
University of Bristol, School of Earth Sciences, Wills Memorial Building, Queens Road, Clifton, BS8 1RJ, UK
*
Author for correspondence: M. B. Matthews, E-mail: [email protected]
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Abstract

Electron beam-induced carbon contamination is a balance between simultaneous deposition and erosion processes. Net erosion rates for a 25 nA 3 kV beam can reduce a 5 nm C coating by 20% in 60 s. Measurements were made on C-coated Bi substrates, with coating thicknesses of 5–20 nm, over a range of analysis conditions. Erosion showed a step-like increase with increasing electron flux density. Both the erosion rate and its rate of change increase with decreasing accelerating voltage. As the flux density decreases the rate of change increases more rapidly with decreasing voltage. Time-dependent intensity (TDI) measurements can be used to correct for errors, in both coating and substrate quantifications, resulting from carbon erosion. Uncorrected analyses showed increasing errors in coating thickness with decreasing accelerating voltage. Although the erosion rate was found to be independent of coating thickness this produces an increasing absolute error with decreasing starting thickness, ranging from 1.5% for a 20 nm C coating on Bi at 15 kV to 14% for a 5 nm coating at 3 kV. Errors in Bi Mα measurement are <1% at 5 kV or above but increase rapidly below this, both with decreasing voltage and increasing coating thickness to 20% for a 20 nm coated sample at 3 kV.

Keywords

carbon erosionlow voltageelectron probe microanalysisthin filmcoating
Type
Materials Science Applications
Information
Microscopy and Microanalysis , Volume 24 , Issue 6 , December 2018 , pp. 612 - 622
Copyright
© Microscopy Society of America 2018 

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Footnotes

Cite this article: Matthews MB, Kearns SL and Buse B (2018) Electron Beam-Induced Carbon Erosion and the Impact on Electron Probe Microanalysis. Microsc Microanal. 24(6), 612–622. doi: 10.1017/S1431927618015398

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