Low Voltage STEM for High-Resolution EDS and EELS

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Low Voltage STEM for High-Resolution EDS and EELS

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Author(s): Raynald Gauvin ¹ , Nicolas Brodusch ¹

Publication date (Electronic): 21 January 2025

Conference name: 13th Asia Pacific Microscopy Congress 2025 (APMC13)

Conference date: 2-7 Febuary 2025

Keywords: Electron Energy Loss spectroscopy, EDS, STEM, High Resolution Imaging

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Abstract

Over the last two decades, scanning transmission electron microscopy (STEM) with lower accelerating voltages compared to the more conventional voltages (200, 300 kV) was explored. Since these low voltages were compatible with the scanning electron microscope (SEM) range, these instruments were naturally selected as potential providers of transmission capabilities at lower costs [ 1]. It was demonstrated that working at voltages between 20 and 30 kV allowed us to produce sufficiently small probes, but at the same time, to significantly increase the scattering in the sample, thus generating images with higher contrasts compared to higher accelerating voltages. The advantage of LV-STEM was recognized quickly and led to the development of commercial systems like the Hitachi SU-9000EA [ 2]. We measured a spatial resolution of 1.9 nm with Cu Ka line versus 1.6 nm in bright-field mode from a line profile across a T1 precipitate (Al2CuLi) in an 80 nm thick Al-Li-Cu alloy specimen [ 3].

The combination of a small probe size with increased interactions with the specimen gives STEM-in-SEM a greater efficiency in mapping specimen composition. Figure 1A shows an EDS map recorded from a carbon nanotube (CNT) covered with TiO2 nanoparticles where the distribution of those particles as well as the iron seeds inside the CNT are very well resolved with high contrast. Similarly, this increase in scattering allows the recording of high-quality elemental maps of lithium in an AA2099 Al-Cu-Li alloy ( Figure 1C) using the EELS 3-window method ( Figure 1B). It is seen that the T1 plates nucleate at the boundaries of the Al ₃Zr phases, the white one in the HAADF image. Work to quantify Li in these maps is underway.

Figure 1.

(A) EDS map of a CNT covered with TiO2 nanoparticles with the corresponding SE image, (B) Principle of the 3-windows method with Li EELS spectrum on SU-9000EA, and (C) HAADF image and elemental & jump ratio maps from an AA2099-T8 condition alloy showing the lithium-based precipitates. Note that no smoothing was applied to the EDS map in A.

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Publication date (Electronic): 21 January 2025

Electronic Location Identifier: e245

Affiliations

[1 ]Department of Mining and Material Engineering, McGill University, Montréal, Québec, Canada

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Raynald Gauvin https://orcid.org/0000-0003-2513-3128

Nicolas Brodusch https://orcid.org/0000-0003-3181-3963

Article

DOI: 10.14293/APMC13-2025-0245

SO-VID: 33472bf7-d188-4f83-b7b5-507651efcc51

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Published under Creative Commons Attribution 4.0 International ( CC BY 4.0). Users are allowed to share (copy and redistribute the material in any medium or format) and adapt (remix, transform, and build upon the material for any purpose, even commercially), as long as the authors and the publisher are explicitly identified and properly acknowledged as the original source.

Conference name: 13th Asia Pacific Microscopy Congress 2025

Conference acronym: APMC13

Conference number: 13

Conference location: Brisbane, Australia

Conference date: 2-7 Febuary 2025

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References

Probst C, Gauvin R, Drew RAL. Micron. 2007;38(4):402–8.
Konno, M., et al. (2014). Ultramicroscopy 145: 28–35.
Brodusch N, Gauvin R. Microscopy and Microanalysis. 2021;27(S1):1318–20.

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[1] Probst C, Gauvin R, Drew RAL. Micron. 2007;38(4):402–8.

[2] Konno, M., et al. (2014). Ultramicroscopy 145: 28–35.

[3] Brodusch N, Gauvin R. Microscopy and Microanalysis. 2021;27(S1):1318–20.

Low Voltage STEM for High-Resolution EDS and EELS

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