Development of electrostatic spherical aberration corrector using annular and circular electrodes

The spherical aberration corrector for high-resolution electron microscopes has been newly designed and constructed. This aberration correction device is formed by an electrostatic lens consisted of only two electrodes having annular and circular holes and a constant-voltage supply. We call it ‘annular and circular electrodes (ACE) corrector’. The ACE corrector has big advantages in easy alignment and very low-cost over the conventional Cs-correctors. In this study, we have constructed the corrector for the scanning transmission electron microsope (STEM) probe-forming optical system. The developed device is very small (less than several tens millimeter) so that this can be assembled at the tip of the conventional aperture holder and installed in a 200kV-STEM column. In experiments using specimens of nanocrystals, we have successfully controlled the spatial resolution of the dark-field STEM images by changing the voltage applied to the corrector and also have imaged lattice fringes. These results clearly demonstrate that our developed device can correct effectively the inherent aberration of the objective lens of the STEM. Copyright © 2016 John Wiley & Sons, Ltd.