0627726 - FZÚ 2026 RIV US eng J - Článek v odborném periodiku
Zich, Jan - Sojka, A. - Levinský, Petr - Míšek, Martin - Ahn, Kyo-Hoon - Navrátil, J. - Hejtmánek, Jiří - Knížek, Karel - Holý, V. - Nuzhnyy, Dmitry - Borodavka, Fedir - Kamba, Stanislav - Drašar, Č.
Phonon properties and unconventional heat transfer in a quasi-two-dimensional Bi₂O₂Se crystal.
Physical Review Materials. Roč. 9, č. 5 (2025), č. článku 054603. ISSN 2475-9953. E-ISSN 2475-9953
Grant CEP: GA MŠMT(CZ) EH22_008/0004594; GA ČR(CZ) GA22-05919S
Institucionální podpora: RVO:68378271
Klíčová slova: quasi-2D semiconductors * infrared and Raman spectroscopy * density functional theory calculations * heat capacity * heat conductivity
Obor OECD: Condensed matter physics (including formerly solid state physics, supercond.)
Impakt faktor: 3.1, rok: 2023 ; AIS: 0.988, rok: 2023
Způsob publikování: Omezený přístup
Web výsledku:
https://doi.org/10.1103/PhysRevMaterials.9.054603DOI: https://doi.org/10.1103/PhysRevMaterials.9.054603

Bi2O2Se belongs to a group of quasi-2D semiconductors that can replace silicon in future high-speed/low-power electronics. However, the correlation between crystal/band structure and other physical properties still eludes understanding: carrier mobility increases non-intuitively with carrier concentration, the observed T2 temperature dependence of resistivity lacks explanation. Moreover, a very high relative out-of-plane permittivity of about 150 has been reported in the literature. A proper explanation for such a high permittivity is still lacking. We have performed infrared (IR) reflectivity and Raman scattering experiments on a large perfect single crystal with defined mosaicity, carrier concentration, and mobility. Five of the eight phonons allowed by factor group theory have been observed and their symmetries determined. The IR spectra show that the permittivity measured in the tetragonal plane is as high as εr≈500, and this high value is due to a strong polar phonon with a low frequency of ∼34 cm-1 (∼1 THz). Such an unusually high permittivity allows the screening of charge defects, leading to the observation of high electron mobility at low temperatures. It also allows effective modulation doping providing a platform for high-performance 2D electronics. DFT calculations suggest the existence of a very low-frequency acoustic phonon ∼14 cm-1 (∼0.4 THz). Both the low-frequency phonons cause anomalous phonon DOS, which is reflected in the unconventional temperature dependence of the heat capacity, Cp≈T3.5. The temperature-dependent, two-component group velocity is proposed to explain the unusual temperature dependence of the thermal conductivity, k≈T1.5.
Trvalý link: https://hdl.handle.net/11104/0366522
Vědecká data: Zenodo