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Charge Neutralization in the ESEM for Quantitative X-ray Microanalysis

Published online by Cambridge University Press:  01 December 2004

Robert A. Carlton ,
Charles E. Lyman  and
James E. Roberts
Robert A. Carlton
Affiliation:
Rhone-Poulenc Rorer, Collegeville, PA 19426, USA
Charles E. Lyman
Affiliation:
Lehigh University, Department of Materials Science and Engineering, Bethlehem, PA 18015, USA
James E. Roberts
Affiliation:
Lehigh University, Department of Chemistry, Bethlehem, PA 18015, USA
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Abstract

Quantitative chemical analysis by energy-dispersive X-ray spectrometry (EDS) in the environmental scanning electron microscope (ESEM) is difficult. This analysis is complicated by the spread of the electron beam by chamber gas molecules and the necessity for surface charge neutralization. Without charge neutralization, errors in quantitative analysis can range up to 15–20% relative. It is possible to achieve the error expected of traditional EDS, ±5% relative error, using a newly developed surface charge neutralization scheme for the ESEM. Estimates of accuracy and precision are based on studies of the National Bureau of Standards (now National Institutes for Science and Technology) Standard Reference Material 482, a series of certified copper–gold alloys. The scheme for charge neutralization requires an independent path to ground at or near the surface of the specimen. The current through the ground path must be maintained at zero by adjusting the voltage on the Gaseous Secondary Electron DetectorTM when the sample chamber is at a gas pressure of 1–2 torr. This procedure forms the exact number of chamber gas positive ions to neutralize negative electrical charge on the specimen surface from electron bombardment.

Keywords

environmental scanning electron microscopyenergy dispersive X-ray spectrometrycharge neutralizationquantitative analysiscopper–gold alloysNIST SRM 482
Type
Research Article
Information
Microscopy and Microanalysis , Volume 10 , Issue 6 , December 2004 , pp. 753 - 763
Copyright
© 2004 Microscopy Society of America

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