Practical Electron Microscopy and Database

To surpass the resolution limit of electron microscopes is possible only by lifting one of the constraints of the Scherzer theorem, for instance by deviating from rotational symmetry of the electron lenses. This can be done with multipole correctors such as quadrupoles, hexapoles, octopoles correctors etc.

By employing an aberration corrector consisting of electrostatic and magnetic quadrupoles and octupoles, an actual reduction of the spatial resolution limit by a factor of approximately three was first achieved by Zach and Haider [1] in an LVSEM (low voltage scanning electron microscope) in 1995. However, it had not been able to use this type of correctors for imaging extended object areas in TEMs due to the large field (off-axial) aberrations of the corrector.