Halogenation of SiGe monolayers: robust changes in electronic and thermal transport

Vaishali Sharma , Hardik L. Kagdada , Prafulla K. Jha , Piotr Śpiewak , Krzysztof Kurzydłowski

Abstract

Phonon and electronic transport of buckled structured SiGe monolayer and halogenated SiGe monolayers (X2–SiGe, X = F, Cl, and Br) are investigated for the first-time using ab initio density functional theory (DFT). The phonon calculations reveal complete dynamical stability of SiGe and fluorinated (F2–SiGe) monolayers in contrast to earlier reported works, where a small magnitude of imaginary frequency in SiGe monolayer near the zone centre of the Brillouin zone (BZ) is observed. The phonon calculations of chlorinated and brominated SiGe reveal no dynamical stability even with very high convergence parameters and better computational accuracy. The lower value of lattice thermal conductivity in the case of F2–SiGe is attributed to the strong phonon anharmonic scattering and larger contribution of the three phonon process to anharmonic scattering. The semimetallic nature of the SiGe monolayer turns to semiconducting after halogenation. We have also calculated the electron relaxation time to study their precise thermoelectric parameters. The enhancement of the Seebeck coefficient and reduction in lattice thermal conductivity in the SiGe monolayer is observed after halogenation which results in the improvement of the thermoelectric figure of merit (ZT). The room temperature figure of merit, ZT, which is 0.112 for the SiGe monolayer, enhances significantly to 0.737 after addition of fluorine atoms. Our study suggests that the halogenation of two-dimensional materials can improve their thermoelectric properties.
Author Vaishali Sharma
Vaishali Sharma,,
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, Hardik L. Kagdada
Hardik L. Kagdada,,
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, Prafulla K. Jha
Prafulla K. Jha,,
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, Piotr Śpiewak
Piotr Śpiewak,,
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, Krzysztof Kurzydłowski (FME / DMPE)
Krzysztof Kurzydłowski,,
- Department of Material and Production Engineering
Journal seriesPhysical Chemistry Chemical Physics, ISSN 1463-9076, e-ISSN 1463-9084, (N/A 100 pkt)
Issue year2019
Vol21
No35
Pages19488-19498
Publication size in sheets0.5
ASJC Classification1606 Physical and Theoretical Chemistry; 3100 General Physics and Astronomy
DOIDOI:10.1039/C9CP03822A
Internal identifierROC 19-20
Languageen angielski
Score (nominal)100
Score sourcejournalList
ScoreMinisterial score = 100.0, 12-02-2020, ArticleFromJournal
Publication indicators Scopus SNIP (Source Normalised Impact per Paper): 2016 = 1.117; WoS Impact Factor: 2018 = 3.567 (2) - 2018=3.963 (5)
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