Quantitative electric field mapping between electrically biased needles by scanning transmission electron microscopy and electron holography

Jean Felix Dushimineza; Janghyun Jo; Rafal E Dunin-Borkowski; Knut Müller-Caspary

doi:10.1016/j.ultramic.2023.113808

Quantitative electric field mapping between electrically biased needles by scanning transmission electron microscopy and electron holography

Ultramicroscopy. 2023 Nov:253:113808. doi: 10.1016/j.ultramic.2023.113808. Epub 2023 Jul 4.

Authors

Jean Felix Dushimineza¹, Janghyun Jo², Rafal E Dunin-Borkowski², Knut Müller-Caspary³

Affiliations

¹ Department of Chemistry and Centre for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstrasse 11, 81377 Munich, Germany; Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Jülich, 52425 Jülich, Germany.
² Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Jülich, 52425 Jülich, Germany.
³ Department of Chemistry and Centre for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstrasse 11, 81377 Munich, Germany; Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Jülich, 52425 Jülich, Germany. Electronic address: k.mueller-caspary@cup.lmu.de.

PMID: 37453211
DOI: 10.1016/j.ultramic.2023.113808

Abstract

Stray electric fields in free space generated by two biased gold needles have been quantified in comprehensive finite-element (FE) simulations, accompanied by first moment (FM) scanning TEM (STEM) and electron holography (EH) experiments. The projected electrostatic potential and electric field have been derived numerically under geometrical variations of the needle setup. In contrast to the FE simulation, application of an analytical model based on line charges yields a qualitative understanding. By experimentally probing the electric field employing FM STEM and EH under alike conditions, a discrepancy of about 60% became apparent initially. However, the EH setup suggests the reconstructed phase to be significantly affected by the perturbed reference wave effect, opposite to STEM where the field-free reference was recorded subsequently with unbiased needles in which possibly remaining electrostatic influences are regarded as being minor. In that respect, the observed discrepancy between FM imaging and EH is resolved after including the long-range potential landscape from FE simulations into the phase of the reference wave in EH.

Keywords: 4D-STEM; Electric field mapping; Finite-element analysis; First-moment STEM; Multislice; Off-axis electron holography; Perturbed reference wave effect.