Effective IMFP of thin samples via the time-of-flight method

0567527 - ÚPT 2023 CZ eng A - Abstrakt
Zouhar, Martin - Daniel, Benjamin - Konvalina, Ivo - Paták, Aleš - Piňos, Jakub - Materna Mikmeková, Eliška
Effective IMFP of thin samples via the time-of-flight method.
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. 168. ISBN 978-80-11-02253-2.
[Multinational Congress on Microscopy /16./. 04.09.2022-09.09.2022, Brno]
Grant CEP: GA ČR(CZ) GA22-34286S
Institucionální podpora: RVO:68081731
Klíčová slova: time‑of‑flight spectrometer * SLEEM * inelastic mean free path
Obor OECD: Electrical and electronic engineering
https://www.16mcm.cz/wp-content/uploads/2022/09/16MCM-abstract-book.pdf

We built a custom ultra-high vacuum scanning low energy electron microscope. It allows us to measure transmitted electron spectra using the time-of-flight (TOF) method. The cathode-lens
principle, applying voltage bias to the sample (stage), allows us to measure at different landing energies ranging from 5 keV down to few eV. The setting of the voltages on active components can be optimised with respect to different quantities, e.g. length of the TOF spectra in the time-domain, keeping detected momentum transfer comparable across different landing energies etc. We reconstruct the hyper-spectral data, TOF spectrum for each pixel in each scan of selected frames, from the collected primary data - a set of timestamps. Single TOF spectrum is obtained by selecting the region of interest, pixels corresponding to the best quality of the sample, and simply adding up the spectra from all the selected pixels. We present the methodology of the data processing and results obtained for a commercial single-layer graphene sample from the Ted Pella company. The experimental data were complemented by the density-functional theory and the many-body perturbation theory simulations and they corroborate our measurements and data processing methods. We use the experimental data to estimate inelastic mean free path (IMFP) using the log-ratio method to sample the energy-profile of the IMFP within the regime of low landing energies. The resulting effective IMFP values for a single-layer graphene are in good agreement with existing literature. We plan to study other 2D and thin materials of scientific and commercial interest as well.
Trvalý link: https://hdl.handle.net/11104/0338780