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On the Effects of Spherical Aberration and Aperture Misalignment on the Formation of Small Electron Probes

Published online by Cambridge University Press:  02 July 2020

Anthony J. Garratt-Reed ,
Graham Cliff  and
Peter B. Kenway
Anthony J. Garratt-Reed
Affiliation:
Center for Materials Science and Engineering, MIT, Cambridge, MA, 02139, USA
Graham Cliff
Affiliation:
Manchester Materials Science Centre, Grosvenor Street, Manchester, Ml 7HS, UK
Peter B. Kenway
Affiliation:
Manchester Materials Science Centre, Grosvenor Street, Manchester, Ml 7HS, UK
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Extract

A major reason for performing microanalysis in the Field-Emission Gun Scanning Transmission Electron Microscope (FEG-STEM) is the very high spatial resolution of the information obtained. It has been estimated that in ideal cases, energy-dispersive x-ray analysis in such an instrument can provide 0.1 wt.% detection sensitivity for an element in a region about 1.5nm in diameter of a foil about 30nm thick. It is obvious that such performance requires that the instrument be properly adjusted, and hence that the probe-forming characteristics be fully understood.

There are three fundamental limits on the minimum size of an electron probe, these being i) the geometrical demagnification of the source, ii) diffraction at the beam-limiting aperture, and iii) spherical aberration in the probe-forming lens. In addition, misalignment of the beam-limiting aperture will result in probe aberrations.

Type
Advances in Instrumentation and Performance
Information
Microscopy and Microanalysis , Volume 4 , Issue S2: Proceedings: Microscopy & Microanalysis '98, Microscopy Society of America 56th Annual Meeting, Microbeam Analysis Society 32nd Annual Meeting, Atlanta, Georgia July 12-16, 1998 , July 1998 , pp. 392 - 393
Copyright
Copyright © Microscopy Society of America

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References

1.Garratt-Reed, A J., Scanning Electron Microscopy/1985/1, 21–29Google Scholar
2.Crewe, A. V., J. Microscopy 178 (1995) 93–100CrossRefGoogle Scholar
3.Kenway, P. B. and Cliff, G., Electron Microscopy and Analysis 1983, 83–86Google Scholar
4. This work was supported in part by an EPSRC Visiting Fellowship (to AJG-R) and in part by the US National Science Foundation through MRSEC Grant number DMR-9400334 to the Center for Materials Science and Engineering at MIT.Google Scholar