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For electron microscopes without aberration corrections, the higher-order terms in Equation 3740 are overwhelmed by the positive, third-order spherical aberration and thus, we only need to consider the aberration coefficients up to third-order. However, for corrected microscopes the higher-order terms becomes dominant.
|
No Aberration Correction
|
Aberration Corrected |
Third order
aberrations corrected |
Fifth-order aberration-corrected |
Illumination aperture size |
Small |
Larger |
|
Beam current |
Lower |
Six-fold increase for the same probe size (comparing with no aberration correction) [2] |
A factor of 100x increase for the same probe size (comparing with no aberration correction) [3] |
Time for chemical mapping |
Take
over an hour [1] |
Take shorter times |
EELS Measurement |
Better electron collection by EEL spectrometer |
Most of electron beam may fall outside the entrance aperture of the EEL spectrometer if the collection optics are improved |
[1] K. Kimoto, et al., Nature 450, 702 (2007).
[2] P. E. Batson, N. Dellby, O. L. Krivanek, Nature 418, 617 (2002).
[3] D. A. Muller, et al., Science, in press Feb 22 (2008).
|