The Electron Optical Performance of the Gemini Lens Design for Low Voltage Scanning Electron Microscope

M. A. Al-Khashab, N. S. Hujazie


The superb resolution at low beam energies, down to 100 eV, is achieved by employing a compound lens which was used recently as an objective lens in low-voltage SEM, called Gemini lens.
A new program has been devised in FORTRAN language in order to compute the objective focal properties for the compound lens. It has been noticed that an improvement is achieved in the objective focal properties, especially at low beam energies, such as the aberration coefficients. The aberration coefficients achieved by our compound lens at beam voltage of 100 V are found to be lower than those achieved by pure magnetic lens by a factor of almost half. (i.e. Cs = 1.15 mm, Cc = 0.78 mm, W. D = 4 mm and   10 nm).
The results of the compound lens of our preferable design were compared with the results in the available published papers and found to be in good agreement over a wide range of applied voltage.


Compound Lens, Gemini Objective Lens, Ultra-High Performance Objective Lens, Low-Voltage Scanning Electron Microscope (SEM)

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