Resolution improvement of low-voltage scanning electron microscope by bright and monochromatic electron gun using negative electron affinity photocathode

The scanning electron microscope (SEM) is a powerful tool for analyzing the surface of various specimens. SEM observation at low voltage, which is typically lower than the 1 kV range, is very effective for obtaining surface information of specimens. However, at the low voltage range, resolution is r...

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Bibliographic Details
Published in:Journal of applied physics 2020-04, Vol.127 (16)
Main Authors: Morishita, Hideo, Ohshima, Takashi, Kuwahara, Makoto, Ose, Yoichi, Agemura, Toshihide
Format: Article
Language:English
Subjects:
Adsorbates
Affinity
Applied physics
Brightness
Electron affinity
Electron guns
Electron microscopes
Electron sources
Emitters
Emitters (electron)
Field emission
Low voltage
Negative electron affinity
Photocathodes
Scanning electron microscopy
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Summary:The scanning electron microscope (SEM) is a powerful tool for analyzing the surface of various specimens. SEM observation at low voltage, which is typically lower than the 1 kV range, is very effective for obtaining surface information of specimens. However, at the low voltage range, resolution is restricted by the brightness and energy spread of electron sources. Therefore, to improve the resolution, a bright and monochromatic electron source is indispensable. In this work, we focused on an electron gun with a negative electron affinity photocathode using p-type GaAs and Cs–O adsorbates. The resolution of a prototype SEM was improved by approximately 16% compared with a SEM using a conventional Schottky emission (SE)-type emitter at the acceleration voltage of 1 kV. In addition, results showed that the measured brightness was as high as an SE-type emitter (∼107 A/m2/sr/V) and the estimated energy spread was less than 0.2 eV, which was narrower than that of a cold field emission-type emitter.
ISSN:0021-8979
1089-7550
DOI:10.1063/5.0005714