Phonon properties and unconventional heat transfer in a quasi-two-dimensional Bi2O2Se crystal

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F68378271%3A_____%2F25%3A00627726" target="_blank" >RIV/68378271:_____/25:00627726 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216275:25310/25:39922910 RIV/00216224:14310/25:00141326 RIV/00216208:11320/25:10499663

Výsledek na webu

<a href="https://doi.org/10.1103/PhysRevMaterials.9.054603" target="_blank" >https://doi.org/10.1103/PhysRevMaterials.9.054603</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1103/PhysRevMaterials.9.054603" target="_blank" >10.1103/PhysRevMaterials.9.054603</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Phonon properties and unconventional heat transfer in a quasi-two-dimensional Bi2O2Se crystal

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

Phonon properties and unconventional heat transfer in a quasi-two-dimensional Bi2O2Se crystal

Popis výsledku anglicky

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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10302 - Condensed matter physics (including formerly solid state physics, supercond.)

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2025

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Physical Review Materials

ISSN

2475-9953

e-ISSN

2475-9953

Svazek periodika

9

Číslo periodika v rámci svazku

5

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

9

Strana od-do

054603

Kód UT WoS článku

001495036600002

EID výsledku v databázi Scopus

2-s2.0-105004739038