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Charge Contrast Imaging of Gibbsite Using the Variable Pressure SEM

Published online by Cambridge University Press:  01 December 2004

Kevin Robertson ,
Raynald Gauvin  and
James Finch
Kevin Robertson
Affiliation:
Department of Mining, Metals and Materials Engineering, McGill University, Montréal, Québec H3A 2B2, Canada
Raynald Gauvin
Affiliation:
Department of Mining, Metals and Materials Engineering, McGill University, Montréal, Québec H3A 2B2, Canada
James Finch
Affiliation:
Department of Mining, Metals and Materials Engineering, McGill University, Montréal, Québec H3A 2B2, Canada
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Abstract

The variable pressure scanning electron microscope (VP-SEM) allows imaging of insulators without the need for a conductive coating, due to charge neutralization at the surface from recombination of positive ions and surface electrons. Varying certain parameters such as pressure, bias, and working distance creates incomplete neutralization, and localized charging develops called charge contrast. Although the exact mechanism creating charge contrast imaging (CCI) is unknown, it is agreed that it is related to an optimum charge compensation. The behavior of the CCI is still vague, which presents a problem for determining the mechanisms. This article provides user-friendly methods of finding the optimum levels of charge contrast in the VP-SEM. We show that the CCI is obtained at optimum operating conditions where the specimen current is between 2.5 nA and 3.5 nA. The specimen current is a function of secondary electrons (SE) emission and ionization potential, producing an ion flux. Therefore an optimum specimen current represents the balanced conditions of SE emission and ion flux. Controlling the pressure, working distance, bias, scan rate, and beam current allows the microscopist to set the specimen current at this optimum level for charge contrast imaging. All the work was performed on gibbsite using the S3000N VP-SEM from Hitachi.

Keywords

variable pressure scanning electron microscopecharge contrast imaginggibbsiteenvironmental secondary electron detectorcontrast measurement
Type
Research Article
Information
Microscopy and Microanalysis , Volume 10 , Issue 6 , December 2004 , pp. 721 - 732
Copyright
© 2004 Microscopy Society of America

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References

REFERENCES

Baroni, T.C. (2001). A microstructural investigation of gibbsite crystallization in bayer liquors. Ph.D. Thesis. University of Western Australia.
Cazaux, J. (1986). Some considerations on the electric field induced in insulators by electron bombardement. J Appl Phys 59, 1418–1430.Google Scholar
Craven, J.P., Baker, F.S., Thiel, B.L., & Donald, A.M. (2002). Consequences of positive ions upon imaging in low vacuum scanning electron microscopy. J Microsc 205, 96–105.Google Scholar
Danilatos, G.D. (1990). Mechanisms of detection and imaging in the ESEM. J Microsc 160, 9–19.Google Scholar
Danilatos, G.D. (1991). Review and outline of environmental SEM at present. J Microsc 162, 391–402.Google Scholar
Farley, A.N. & Shah, J.S. (1990a). Primary considerations for image enhancement in high pressure scanning electron microscopy. J Microsc 158, 379–388.Google Scholar
Farley, A.N. & Shah, J.S. (1990b). Primary considerations for image enhancement in high pressure scanning electron microscopy. J Microsc 158, 389–401.Google Scholar
Farley, A.N. & Shah, J.S. (1991). High-pressure scanning electron microscopy of insulating materials: A new approach. J Microsc 164, 107–126.Google Scholar
Fletcher, A.L., Thiel, B.L., & Donald, A.M. (1997). Amplification measurements of alternative imaging gases in the environmental SEM. J Phys D: Appl Phys 30, 2249–2257.Google Scholar
Fletcher, A.L., Thiel, B.L., & Donald, A.M. (2000). Signal components in the environmental scanning electron microscope. J Microsc 196, 26–34.Google Scholar
Goldstein, J.I., Newbury, D.E., Echlin, P., Joy, D.C., Romig, A.D., Lyman, C.E., & Lifshin, E. (1992). Scanning Electron Miroscopy and X-Ray Microanalysis. New York: Plenum Press.
Griffin, B.J. (1997). A new mechanism for the imaging of crystal structure in non-conductive materials: An application of charge-induced contrast in the environmental scanning electron microscope (ESEM). Microsc Microanal 3, 1197–1198.Google Scholar
Griffin, B.J. (2000). Charge contrast imaging of material growth and defects in ESEM-linking electron emission and cathodoluminescence. Scanning 22, 234.Google Scholar
Mohan, A., Khanna, J., Hwu, J., & Joy, D.C. (1998). Secondary electron imaging in the Variable Pressure Scanning Electron Microscope. Scanning 20, 436–441.Google Scholar
Moncrieff, D.A., Robinson, V.N.E., & Harris, L.B. (1978). Charge neutralisation of insulating surfaces in the SEM by gas ionization. J Phys D: Appl Phys 11, 2315–2325.Google Scholar
Thiel, B.L., Bache, I.C., Fletcher, A.L., Meredith, P., & Donald, A.M. (1997). An improved model for gaseous amplification in the environmental SEM. J Microsc 187, 143–157.Google Scholar
Toth, B.L., Kucheyev, S.O., Williams, J.S., Jagadish, C., Phillips, M.R., & Li, G. (2000). Imaging charge trap distributions in GaN using environmental scanning electron microscopy. Appl Phys Lett 77, 1342–1344.Google Scholar
Toth, M., Daniels, D.R., Thiel, B.L., & Donald, A.M. (2002a). Quantification of electron-ion recombination in an electron-beam-irradiated gas capacitor. J Phys D: Appl Phys 35, 1796–1804.Google Scholar
Toth, M., Phillips, M.R., Craven, J.P., Thiel, B.L., & Donald, A.M. (2002b). Electric fields produced by electron irradiation of insulators in a low vacuum environment. J Appl Phys 91, 4492–4499.Google Scholar
Toth, M., Phillips, M.R., Thiel, B.L., & Donald, A.M. (2002c). Electron imaging of dielectrics under simultaneous electron-ion irradiation. J Appl Phys 91, 4479–4491.Google Scholar
Toth, M., Thiel, B.L., & Donald, A.M. (2002d). On the role of electron-ion recombination in low vacuum scanning electron microscopy. J Microsc 205, 86–95.Google Scholar
Watt, G.R., Griffin, B.J., & Kinny P.D. (2000). Charge contrast imaging of geological materials in the environmental scanning electron microscope. Am Mineral 85, 1784–1794.Google Scholar