Overcoming resolution loss due to thermal magnetic field fluctuations from phase plates in transmission electron microscopy

Jeremy J Axelrod; Petar N Petrov; Jessie T Zhang; Jonathan Remis; Bart Buijsse; Robert M Glaeser; Holger Mȕller

doi:10.1016/j.ultramic.2023.113730

Overcoming resolution loss due to thermal magnetic field fluctuations from phase plates in transmission electron microscopy

Ultramicroscopy. 2023 Jul:249:113730. doi: 10.1016/j.ultramic.2023.113730. Epub 2023 Mar 29.

Authors

Jeremy J Axelrod¹, Petar N Petrov², Jessie T Zhang³, Jonathan Remis², Bart Buijsse⁴, Robert M Glaeser⁵, Holger Mȕller²

Affiliations

¹ Department of Physics, University of California Berkeley, Berkeley, CA 94720, USA; Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, USA. Electronic address: jaxelrod@berkeley.edu.
² Department of Physics, University of California Berkeley, Berkeley, CA 94720, USA; Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, USA.
³ Department of Physics, University of California Berkeley, Berkeley, CA 94720, USA.
⁴ Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG, Eindhoven, the Netherlands.
⁵ Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, USA; Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA 94720, USA.

PMID: 37011498
DOI: 10.1016/j.ultramic.2023.113730

Abstract

We identify thermal magnetic field fluctuations, caused by thermal electron motion ("Johnson noise") in electrically conductive materials, as a potential resolution limit in transmission electron microscopy with a phase plate. Specifically, resolution loss can occur if the electron diffraction pattern is magnified to extend phase contrast to lower spatial frequencies, and if conductive materials are placed too close to the electron beam. While our initial implementation of a laser phase plate (LPP) was significantly affected by these factors, a redesign eliminated the problem and brought the performance close to the expected level. The resolution now appears to be limited by residual Johnson noise arising from the electron beam liner tube in the region of the LPP, together with the chromatic aberration of the relay optics. These two factors can be addressed during future development of the LPP.