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Electrochemical Etching and Characterization of Sharp Field Emission Points for Electron Impact Ionization
Published on: July 12, 2016
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Properties of electrostatic correcting systems with annular apertures.
Tetsuji Kodama1, Tadahiro Kawasaki2, Takashi Ikuta3
1Faculty of Science and Technology, Meijo University, Nagoya 468-8502, Japan.
Microscopy (Oxford, England)
|November 12, 2019
Summary
Electron microscopes use special apertures to correct spherical aberration, a common lens defect. This study provides analytical formulas for these correcting effects in electron imaging.
Area of Science:
- Physics
- Electron Optics
- Microscopy
Background:
- Spherical aberration is an inherent limitation in electron lenses, degrading image quality.
- Conventional apertures do not correct for spherical aberration in electron microscopes.
Purpose of the Study:
- To theoretically investigate image formation in electron microscopes using circular hole and annular apertures.
- To analyze the aberration-correcting effects of these apertures.
Main Methods:
- Theoretical study of electron beam interaction with electrostatic fields generated by apertures.
- Application of the Davisson-Calbick formula for calculating focal length.
Main Results:
- Circular hole and annular apertures generate electrostatic fields that correct spherical aberration.
- The deflection angle's dependence on distance from the optical axis provides a correcting mechanism.
- Analytical formulae derived for the aberration-correcting effects.
Conclusions:
- The studied apertures offer a method to correct for spherical aberration in electron microscopy.
- The electrostatic field's properties enable a stronger-than-linear correction, improving image fidelity.
