Disadvantages of Monochromation System in EMs
- Practical Electron Microscopy and Database -
- An Online Book -


This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.


Although the monochromation systems in EMs (electron microscopes) can significantly improve the energy resolution of the systems, they do have disadvantages such as a loss of beam current, enlarged probe size, high cost, and lack of retrograded potential. The origin of low beam current or enlarged probe size is that a reduction in brightness ([A/Str.m2]) is fundamentally unavoidable in a monochromatized illumination system.

In some laboratories, even though monochromators have been installed in the electron microscopes, the monochromators are turned off for routine work because:
          i) The loss of beam current with monochromators on,
          ii) High energy resolutions (e.g. < 0.5 eV) is not always necessary, for instance, in the case of core-loss spectroscopy, the fine structures in a core-loss spectrum are dominated by lifetime broadening and solid-state effects [1] that normally does not need high resolutions.
          iii) The performance of the monochromator can be degraded by energy instability [2].

Therefore, a TEM without a monochromator may still be the most attractive for EELS.





[1] Mitterbauer, C., Kothleitner, G., Grogger, W., Zandbergen, H., Freitag, B., Tiemeijer, P., Hofer, F., 2003. Electron energy-loss near-edge structures of 3d transition metal oxides recorded at high-energy resolution. Ultramicroscopy 96, 469–480.
[2] Tiemeijer, P.C., Lin, J.H.A.v., Freitag, B.H., Jong, A.F.d., 2002. Monochromized 200 kV (S)TEM. Microsc. Microanal. 8 (Suppl. 2), 70–71.




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