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Insights from Experiment and Theory on Peculiarities of the Electronic Structure and Optical Properties of the Tl2HgGeSe4 Crystal
Insights from Experiment and Theory on Peculiarities of the Electronic Structure and Optical Properties of the Tl2HgGeSe4 Crystal
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Date
2023
Authors
"Tuan V. Vu,* Oleg Khyzhun,* Galyna L. Myronchuk, Mariana Denysyuk, Lyudmyla Piskach, Andrij O. Selezen, Ilona Radkowska, Anatolii O. Fedorchuk, Svitlana S. Petrovska, Vira A. Tkach, and Michał Piasecki*"
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Abstract
"Tl2HgGeSe4 crystal was successfully, for the first time,
synthesized by the Bridgman−Stockbarger technology, and its electronic
structure and peculiarities of optical constants were investigated using both
experimental and theoretical techniques. The present X-ray photoelectron
spectroscopy measurements show that the Tl2HgGeSe4 crystal reveals small
moisture sensitivity at ambient conditions and that the essential covalent
constituent of the chemical bonding characterizes it. The latter suggestion
was supported theoretically by ab initio calculations. The present experiments
feature that the Tl2HgGeSe4 crystal is a high-resistance semiconductor with a
specific electrical conductivity of σ ∼ 10−8 Ω−1 cm−1 (at 300 K). The crystal
is characterized by p-type electroconductivity with an indirect energy band gap of 1.28 eV at room temperature. It was established
that a good agreement with the experiments could be obtained when performing first-principles calculations using the modified
Becke−Johnson functional as refined by Tran−Blaha with additional involvement in the calculating procedure of the Hubbard
amendment parameter U and the impact of spin−orbit coupling (TB-mBJ + U + SO model). Under such a theoretical model, we
have determined that the energy band gap of the Tl2HgGeSe4 crystal is equal to 1.114 eV, and this band gap is indirect in nature.
The optical constants of Tl2HgGeSe4 are calculated based on the TB-mBJ + U + SO model"