Time-of-Flight Spectrometer for Low Landing Energies

0567516 - ÚPT 2023 RIV CZ eng A - Abstract
Konvalina, Ivo - Daniel, Benjamin - Zouhar, Martin - Paták, Aleš - Průcha, Lukáš - Piňos, Jakub - Müllerová, Ilona - Materna Mikmeková, Eliška
Time-of-Flight Spectrometer for Low Landing Energies.
16th Multinational Congress on Microscopy, 16MCM, 04-09 September 2022, Brno, Czech Republic. Book of abstracts. Brno: Czechoslovak Microscopy Society, 2022 - (Krzyžánek, V.; Hrubanová, K.; Hozák, P.; Müllerová, I.; Šlouf, M.). s. 160-161. ISBN 978-80-11-02253-2.
[Multinational Congress on Microscopy /16./. 04.09.2022-09.09.2022, Brno]
R&D Projects: GA TA ČR(CZ) TN01000008
Institutional support: RVO:68081731
Keywords : time‑of‑flight spectrometer * graphene * inelastic mean free path * energy‑loss spectrum
OECD category: Electrical and electronic engineering
https://www.16mcm.cz/wp-content/uploads/2022/09/16MCM-abstract-book.pdf

New technological development and innovations of advanced 2D materials entail high demands on their analysis techniques. A detailed study of electron scattering in solids is essential for the design and diagnostics of the next generation materials, as well as in solid-state physics. The inelastic mean free path (IMFP) is a key parameter of electron scattering in both bulk materials and thin foils. At the Institute of Scientific Instruments of the Czech Academy of Sciences, we designed and assembled an ultra-high vacuum scanning low energy electron microscope (UHV SLEEM). The device is equipped with a time-of-flight (ToF) spectrometer, which operates in transmission mode. This allows us to use both electron microscopy and spectroscopy - powerful tools for obtaining information about the structure and properties of the analyzed materials. We performed extensive experiments on a commercial monolayer graphene to obtain electron energy-loss spectra (EELS) for low landing energies. Graphene has unique properties, including remarkably high transparency and electrical conductivity. This makes it suitable for studying at very low energies in the transmission mode of UHV SLEEM. We focus on the low landing energy interval (200, 800) eV and energy losses up to approximately 40 eV (which covers both π and π+σ graphene plasmon peaks). The experimental data are shown in Figure 1. Applying the log-ratio method on the straight-line segment baseline-corrected EELS, we arrived at the effective IMFP values shown in Figure 2. Theoretical approaches to obtain IMFP include predictive formulas such as TPP-2M or Bethe formula (valid for amorphous materials). One of the main advantages of our UHV SLEEM/ToF system is the possibility of using free-standing ultrathin samples. This eliminates the effect of the substrate and significantly reduces multiple inelastic scattering events. As a result, the analysis of EELS data is greatly simplified. Furthermore, the energy resolution of the ToF spectrometer, 0.5 eV at the landing energy of 50 eV, is more than acceptable for studying a graphene sample and thin foils.
Permanent Link: https://hdl.handle.net/11104/0338771