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Review of Electron-Gas Interactions in the Environmental SEM

Published online by Cambridge University Press:  02 July 2020

B.L. Thiel
B.L. Thiel*
Affiliation:
Polymers and Colloids Group, Cavendish Laboratory, Department of Physics, University of Cambridge, Madingley Road, Cambridge, CB3 OHE, U.K.
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Extract

Understanding the various interactions between electrons and the specimen chamber gas is essential to using environmental and low-vacuum SEM’s to their full potential. The problem can be divided into two main topics: distortion of the primary beam on its way to the sample surface, and amplification of the various electron signals leaving the sample. These issues are important for all low-vacuum SEM’s, regardless of the system design or signal detection method. All instruments must contend with scattering of the primary beam in the gas, and the subsequent effects on resolution, background signals,.and x-ray generation. Similarly, while some instrument designs rely more heavily than others on signal amplification in the gas, all benefit from the concomitant charge neutralisation.

As the electron probe travels through the gas on its way to the specimen, elastic collisions occur with molecules in the gas.[1] Fortunately, for gas pressures of a few torr, the mean free path is on the order of tens of millimetres, and the vast majority of electrons reach the specimen unscattered.

Type
Environmental Scanning Electron Microscopy and Other Wet Work
Information
Microscopy and Microanalysis , Volume 5 , Issue S2: Proceedings: Microscopy & Microanalysis '99, Microscopy Society of America 57th Annual Meeting, Microbeam Analysis Society 33rd Annual Meeting, Portland, Oregon August 1-5, 1999 , August 1999 , pp. 272 - 273
Copyright
Copyright © Microscopy Society of America

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References

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[2] Danilatos, G.D.Adv. Elec. Electron Phys., 78 (1990) 1–102.CrossRefGoogle Scholar

[3] Thiel, B.L., et al.J. Microscopy, 187 (1997) 143–157.CrossRefGoogle Scholar

[4] Fletcher, A.L., et al. J. Microscopy (accepted February 1999).Google Scholar

[5] Fletcher, A.L., et al.J.Phys. D: Appl. Phys., 30 (1997) 2249–2257.CrossRefGoogle Scholar

[6] Thiel, B.L., et al. (submitted to Scanning).Google Scholar

[7] Hwang, H., et al.J. Chem. Phys., 104 (1996) 2956–2966.CrossRefGoogle Scholar

[8] Portions of this work were funded by the BBSRC and Unilever, pic.Google Scholar