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Present Concepts and Designs for Gun Monochromators

Published online by Cambridge University Press:  02 July 2020

F. Kahl  and
E. Voelkl
F. Kahl
Affiliation:
1 Bethel Valley Rd, Oak Ridge National Laboratory, Oak Ridge, TN, 37831
E. Voelkl
Affiliation:
1 Bethel Valley Rd, Oak Ridge National Laboratory, Oak Ridge, TN, 37831
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Abstract

The attainable information in transmission electron microscopes is limited today primarily by chromatic aberrations, because the new generation of spherical aberration correctors has practically eliminated resolution limits caused by spherical aberration. If it would be possible to develop an electron source with 0.2 eV energy width, the limitations of chromatic aberrations could be minimized, and techniques like Electron Energy Loss Spectroscopy (EELS) could provide much more detail on the type of bonding between atoms. At present, the main approach to reduce the energy width of present day field emission electron sources is to incorporate a beam monochromator in the electron gun. The challenge for such a monochromator is not only to provide a small energy width of 0.2 eV or less, but also to preserve the brightness of the gun as much as possible at a level of current sufficient for high resolution imaging on a routine basis.

Over the last few years, several different designs for monochromators have been proposed. All designs are based on energy dispersive components which separate electrons of different energies spatially and eliminate the ones with high energy deviation by means of a selection slit.

Type
TEM Instrument Development (Organized by D. Smith and L. Allard)
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. 922 - 923
Copyright
Copyright © Microscopy Society of America 2001

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