Single scan STEM-EMCD in 3-beam orientation using a quadruple aperture

Hasan Ali; Sharath Kumar Manjeshwar Sathyanath; Cheuk-Wai Tai; Jan Rusz; Toni Uusimaki; Björgvin Hjörvarsson; Thomas Thersleff; Klaus Leifer

doi:10.1016/j.ultramic.2023.113760

Single scan STEM-EMCD in 3-beam orientation using a quadruple aperture

Ultramicroscopy. 2023 Sep:251:113760. doi: 10.1016/j.ultramic.2023.113760. Epub 2023 May 18.

Authors

Hasan Ali¹, Sharath Kumar Manjeshwar Sathyanath², Cheuk-Wai Tai³, Jan Rusz⁴, Toni Uusimaki³, Björgvin Hjörvarsson⁴, Thomas Thersleff³, Klaus Leifer²

Affiliations

¹ Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm, Sweden; Department of Materials Science and Engineering, Uppsala University, Box 534, 75121, Uppsala, Sweden. Electronic address: ali.hasan@angstrom.uu.se.
² Department of Materials Science and Engineering, Uppsala University, Box 534, 75121, Uppsala, Sweden.
³ Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm, Sweden.
⁴ Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden.

PMID: 37285614
DOI: 10.1016/j.ultramic.2023.113760

Abstract

The need to acquire multiple angle-resolved electron energy loss spectra (EELS) is one of the several critical challenges associated with electron magnetic circular dichroism (EMCD) experiments. If the experiments are performed by scanning a nanometer to atomic-sized electron probe on a specific region of a sample, the precision of the local magnetic information extracted from such data highly depends on the accuracy of the spatial registration between multiple scans. For an EMCD experiment in a 3-beam orientation, this means that the same specimen area must be scanned four times while keeping all the experimental conditions same. This is a non-trivial task as there is a high chance of morphological and chemical modification as well as non-systematic local orientation variations of the crystal between the different scans due to beam damage, contamination and spatial drift. In this work, we employ a custom-made quadruple aperture to acquire the four EELS spectra needed for the EMCD analysis in a single electron beam scan, thus removing the above-mentioned complexities. We demonstrate a quantitative EMCD result for a beam convergence angle corresponding to sub-nm probe size and compare the EMCD results for different detector geometries.