第162回先端計測オープンセミナー

7月29日 (金) 11:00~12:00

千現地区　研究本館8階中セミナー室 (811・812室) + オンライン (Zoom)
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Andrew Pratt, University of York

Novel approaches to material analysis using spectro-microscopy of low energy electrons

Low-energy electrons (LEE) play a critical role in a wide range of disciplines, from healthcare applications and additive manufacturing to materials science and surface analysis. Understanding their interaction with matter will help develop novel processes and materials as well as providing deeper insight on unexplained phenomena such as contrast reversal mechanisms, electron reflectivity, and spin injection. LEEs, typically with energies <10 eV, are characteristic of a sample’s composition, electronic structure, and geometry whilst they are also detected as secondary electrons (SEs) in scanning electron microscopy (SEM).

SEMs have for decades utilised the Everhart-Thornley detector in order to attract SEs emitted from a sample and measure their overall yield. Whilst this approach is simple and effective, valuable information on the angular and energy distribution of the emitted electrons is lost. In this presentation, we will outline a novel approach to the detection of LEEs emitted from a sample based on a ‘Bessel box’ analyser (BBA) [1]. This compact device is capable of measuring an entire ejected electron energy spectrum with high resolution in both ultrahigh vacuum and SEM environments, providing a rapid method of performing Auger electron spectroscopy, elastic peak electron spectroscopy, and quantitative secondary electron spectroscopy, in addition to imaging.

We also utilise LEEs in a novel application of scanning tunnelling microscopy that operates in the field-emission regime. This technique, known as scanning field emission microscopy (SFEM), opens up new possibilities for microscopy and spectroscopy at the nanoscale [2]. Adding a BBA to the SFEM allows quantitative measurements of LEE emission and investigation of, for example, how varying the work function of a Cs-doped W(110) surface affects the emitted electron yield [3], and how electrons can ‘skip’ across a surface through quantum reflection under the influence of an applied field [4].

[1] A. Suri et al., J. Microsc. 279, 207 (2020)
[2] D. A. Zanin et al., Proc. R. Soc. A. Math Phys. Eng. Sci. 472, 20160475 (2016)
[3] M. Bodik et al., Ultramicroscopy 238, 113547 (2022)
[4] A. K. Thamm et al., Appl. Phys. Lett. 120, 052403 (2022)