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Towards Sub-Ångstrom Resolution With A 200 Kv TEM By Means of a Cs-Corrector and a Computer Controlled Alignment Procedure

Published online by Cambridge University Press:  02 July 2020

M. Haider  and
S. Uhlemann
M. Haider
Affiliation:
CEOS, Corrected Electron Optical Systems GmbH, Im Neuenheimer Feld 519, D-69120, Heidelberg, FRG
S. Uhlemann
Affiliation:
CEOS, Corrected Electron Optical Systems GmbH, Im Neuenheimer Feld 519, D-69120, Heidelberg, FRG
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Extract

One of the most difficult problems on the way to sub-Ångstrom resolution at a medium accelerating voltage of about 200 kV, the correction of the spherical aberration, has been solved. Already more than fifty years ago, Scherzer showed that the two major axial aberrations, the chromatic and the spherical aberration, can be corrected by a suitable combination of electrostatic and/or magnetic multipole elements. Due to the availability of high-coherent electron sources with a small relative energy width DE/E the necessity of correcting the chromatic aberration can be avoided.

Our solution for spherical aberration correction follows a suggestion by Rose. It is based on two electromagnetic hexapoles and four additional lenses. The principle by which correction is achieved is based on the fact that the primary aberrations of second order of the first hexapole are compensated by the second hexapole element.

Type
Advances in Remote Microscopy, Instrument Automation and Data Storage
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. 50 - 51
Copyright
Copyright © Microscopy Society of America

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References

1Rose, H., Optik 85 (1990) 19Google Scholar
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3Haider, M., Braunshausen, G. and Schwan, E., Optik 99 (1995) 167Google Scholar
4Zemlin, F., Weiss, K., Schiske, P., Kunath, W. and Herrmann, K.-H., Ultramicroscopy 3 (1977) 49CrossRefGoogle Scholar
5Uhlemann, S. and Haider, M., to be published in Ultramicroscopy 1998Google Scholar
6Kabius, B. et. al., Proc. Ann. MSA Meeting, Atlanta (1998)Google Scholar
7 The financial support of this project by the VW-Foundation is gratefully acknowledged.Google Scholar