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Electron Channeling: A Problem for X-Ray Microanalysis in Materials Science

Published online by Cambridge University Press:  16 March 2009

Frederick Meisenkothen ,
Robert Wheeler ,
Michael D. Uchic ,
Robert D. Kerns  and
Frank J. Scheltens
Frederick Meisenkothen*
Affiliation:
Air Force Research Laboratory, Materials Characterization Facility, operated by UES, Inc., Wright Patterson Air Force Base, OH 45433, USA
Robert Wheeler
Affiliation:
Air Force Research Laboratory, Materials Characterization Facility, operated by UES, Inc., Wright Patterson Air Force Base, OH 45433, USA
Michael D. Uchic
Affiliation:
Air Force Research Laboratory, Materials and Manufacturing Directorate, Metals Development Group, Wright Patterson Air Force Base, OH 45433, USA
Robert D. Kerns
Affiliation:
Air Force Research Laboratory, Materials Characterization Facility, operated by UES, Inc., Wright Patterson Air Force Base, OH 45433, USA
Frank J. Scheltens
Affiliation:
Air Force Research Laboratory, Materials Characterization Facility, operated by UES, Inc., Wright Patterson Air Force Base, OH 45433, USA
*
Corresponding author. E-mail: [email protected]
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Abstract

Electron channeling effects can create measurable signal intensity variations in all product signals that result from the scattering of the electron beam within a crystalline specimen. Of particular interest to the X-ray microanalyst are any variations that occur within the characteristic X-ray signal that are not directly related to a specimen composition variation. Many studies have documented the effect of crystallographic orientation on the local X-ray yield; however, the vast majority of these studies were carried out on thin foil specimens examined in transmission. Only a few studies have addressed these effects in bulk specimen materials, and these analyses were generally carried out at common scanning electron microscope microanalysis overvoltages (>1.5). At these overvoltage levels, the anomalous transmission effect is weak. As a result, the effect of electron channeling on the characteristic X-ray signal intensity has traditionally been overlooked in the field of quantitative electron probe microanalysis. The present work will demonstrate that electron channeling can produce X-ray variations of up to 26%, between intensity maxima and minima, in low overvoltage X-ray microanalyses of bulk specimens. Intensity variations of this magnitude will significantly impact the accuracy of qualitative and quantitative X-ray microanalyses at low overvoltage on engineering structural materials.

Keywords

channelingEPMAelectron probe microanalysisX-ray microanalysisWDSEDSanomalous transmissionanomalous absorptionovervoltage
Type
Microanalysis
Information
Microscopy and Microanalysis , Volume 15 , Issue 2 , April 2009 , pp. 83 - 92
Copyright
Copyright © Microscopy Society of America 2009

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