Correction of higher order geometrical aberration by triple 3-fold astigmatism field

A new concept of a spherical aberration correction system using three dodecapoles is proposed. The system compensates for higher order aberration of 6-fold astigmatism, which generally limits a uniform phase area for image forming and probe forming in an electron microscope with a conventional two-h...

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Bibliographic Details
Published in:Journal of electron microscopy 2009-12, Vol.58 (6), p.341-347
Main Authors: Sawada, Hidetaka, Sasaki, Takeo, Hosokawa, Fumio, Yuasa, Shuuichi, Terao, Mitsuhisa, Kawazoe, Muneyuki, Nakamichi, Tomohiro, Kaneyama, Toshikatsu, Kondo, Yukihito, Kimoto, Koji, Suenaga, Kazutomo
Format: Article
Language:English
Subjects:
Aberration
aberration correction
Astigmatism
delta
Forming
Light
Mathematical analysis
Methods
Optics
Optimization
Representations
Ronchigram
Scanning electron microscopy
six-fold astigmatism
trajectory
Transmission electron microscopy
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Summary:A new concept of a spherical aberration correction system using three dodecapoles is proposed. The system compensates for higher order aberration of 6-fold astigmatism, which generally limits a uniform phase area for image forming and probe forming in an electron microscope with a conventional two-hexapole corrector. Triple 3-fold astigmatism field is used to correct the spherical aberration of the objective lens, and the total 3-fold astigmatism is eliminated by their combination. The optimum azimuth relationship among three dodecapoles is calculated to eliminate the 6-fold astigmatism. The principle of the method was verified using a mathematically complex representation. This new concept was experimentally tested with a scanning transmission electron microscope at 60 kV acceleration. The 6-fold astigmatism was certainly compensated and the coherent convergent angle became almost twice compared to a conventional double hexapole system.
ISSN:0022-0744
1477-9986
2050-5701
DOI:10.1093/jmicro/dfp033