[1] P.E. Batson, H.W. Mook,
and P. Kruit, High Brightness
Monochromator for STEM, in International
Union of Microbeam Analysis 2000, edited by D.B. Williams and R.
Shimizu (Institute of Physics, Bristol, 2000), Vol. 165, pp. 213-214. [2] H.W. Mook,
P.E. Batson, and P. Kruit, Monochromator for high
brightness electron guns, in 12th European congress on electron
microscopy, Vol. III, (2000) pp. 315 -316.
Although the EELS spectrometer in this system delivers an energy
resolution of about 50-130meV, the natural width of the room temperature Field
Emission Gun (FEG) electron source is 280-350 meV, so
a full utilization of the spectrometer capability is limited. This can be changed by addition of an
electron monochromator, placed within the gun. A 3 cm long “fringe field” monochromator has been designed and tested for this system.
[1, 2] This device disperses the FEG
source electrons against a 200 nm diameter aperture. The monochromator-spectrometer
combination has shown a 61 meV resolution, while preserving the high brightness
characteristics of the FEG. The left
illustration below shows the intensity of the gun as the source spot is scanned
across the small energy selecting aperture.
