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Effects of Gaseous ion Concentration on Secondary Electron Contrast of Dielectric Materials Imaged in the ESEM

Published online by Cambridge University Press:  02 July 2020

B.L. Thiel ,
M. Toth  and
J.P. Craven
B.L. Thiel
Affiliation:
Polymers and Colloids Group, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 OHE, UK
M. Toth
Affiliation:
Polymers and Colloids Group, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 OHE, UK
J.P. Craven
Affiliation:
Polymers and Colloids Group, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 OHE, UK
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Abstract

An increasing body of experimental evidence indicates that the flux and distribution of gaseous ions significantly affects secondary electron contrast of dielectric materials imaged in low vacuum and environmental scanning electron microscopes. Unusual contrast has been identified in some insulating materials, and attributed to charging effects (1-3). However, as these contrast mechanisms have not been reported in conventional microscopes, it would seem that the ions play an important role in making the contrast manifest. The effects of ions can include the creation of space charge in the gas above the specimen, influencing the charge state of the specimen surface, and electron-ion recombination (possibly leading to energy filtering of emitted secondary electrons). Space charge and surface potential can influence the gain realised in the gas amplification cascade by altering the detector field (4). However, surface potential, and recombination affect the number of electrons injected into the amplification cascade, to give rise to contrast variations in the final image.

Type
Technologists’ Forum: ESEM/Lv/Vp: Imaging at Low Vacuum (Organized by J. Killius)
Information
Microscopy and Microanalysis , Volume 7 , Issue S2: Proceedings: Microscopy & Microanalysis 2001, Microscopy Society of America 59th Annual Meeting, Microbeam Analysis Society 35th Annual Meeting, Long Beach, California August 5-9, 2001 , August 2001 , pp. 790 - 791
Copyright
Copyright © Microscopy Society of America 2001

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References

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6) Craven, J.P. and Baker, F.S., UK Patent application No. 0005717.4, University of Cambridge, and manuscript in preparation.Google Scholar

7) The funding and support of FEI, the Sir Isaac Newton Trust, Schlumberger and the EPSRC are gratefully acknowledged.Google Scholar