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I. Konvalina, B. Daniel, M. Zouhar, A. Paták, I. Müllerová, L. Frank, J. Piňos, L. Průcha, T. Radlička, W.S.M. Werner, E. Mikmeková:
"Low-Energy Electron Inelastic Mean Free Path of Graphene Measured by a Time-of-Flight Spectrometer";
Nanomaterials, 11 (2021), 243501 - 243519.

The detailed examination of electron scattering in solids is of crucial importance for the
theory of solid-state physics, as well as for the development and diagnostics of novel materials,
particularly those for micro- and nanoelectronics. Among others, an important parameter of electron
scattering is the inelastic mean free path (IMFP) of electrons both in bulk materials and in thin
films, including 2D crystals. The amount of IMFP data available is still not sufficient, especially for
very slow electrons and for 2D crystals. This situation motivated the present study, which summarizes
pilot experiments for graphene on a new device intended to acquire electron energy-loss spectra
(EELS) for low landing energies. Thanks to its unique properties, such as electrical conductivity
and transparency, graphene is an ideal candidate for study at very low energies in the transmission
mode of an electron microscope. The EELS are acquired by means of the very low-energy electron
microspectroscopy of 2D crystals, using a dedicated ultra-high vacuum scanning low-energy electron
microscope equipped with a time-of-flight (ToF) velocity analyzer. In order to verify our pilot
results, we also simulate the EELS by means of density functional theory (DFT) and the many-body
perturbation theory. Additional DFT calculations, providing both the total density of states and the
band structure, illustrate the graphene loss features. We utilize the experimental EELS data to derive
IMFP values using the so-called log-ratio method.

time-of-flight spectrometer; inelastic mean free path; density-functional theory; manybody perturbation theory; energy-loss spectrum; density of states; band structure; graphene

http://dx.doi.org/10.3390/nano11092435

https://publik.tuwien.ac.at/files/publik_297231.pdf