TY - JOUR
T1 - Metavalent Bonding Induced Phonon Transport Anomaly in 2D γ-MX (M = Ge, Sn, Pb; X = S, Se, Te) Monolayers
AU - Nair, Surabhi Suresh
AU - Sajjad, Muhammad
AU - Biswas, Kanishka
AU - Singh, Nirpendra
N1 - Publisher Copyright:
© 2023 The Authors. Published by American Chemical Society.
PY - 2023/9/11
Y1 - 2023/9/11
N2 - Exploring thermoelectric materials with captivating chemical bonding and low lattice thermal conductivity (κ
l) is crucial in thermoelectric research. Here, we propose two-dimensional (2D) γ-monochalcogenide (MX; M = Ge, Sn, Pb, and X = S, Se, Te) monolayers as potential thermoelectric materials. The exfoliation energies of γ-MX monolayers fall in the 12-16 meV/Å
2 range, less than graphene (21 meV/Å
2), suggesting their feasible realization through mechanical or chemical exfoliation. The electronic band structures exhibit an indirect band gap ranging from 0.41 eV for γ-PbTe to 0.86 eV for γ-PbS. The metavalent bonding in these monolayers results in an unusual trend in κ
l with atomic mass. Among studied monolayers, the γ-PbTe monolayer exhibits an ultralow room temperature κ
l of 0.49 W/mK, which accounts for its increased anharmonicity and higher scattering rates from acoustic and low-lying optical phonons. Despite having a higher mass than γ-PbS, γ-PbSe demonstrates enhanced κ
l values. Similar anomalous behavior is observed in the case of γ-GeTe (8.57 W/mK), γ-GeSe (3.10 W/mK), γ-SnTe (4.30 W/mK), and γ-SnSe (3.31 W/mK) monolayers. The enhanced κ
l in tellurides is attributed to the high bond stiffness, low charge transfer between M and X atoms, and widening of the phonon gap, which significantly reduces the phonon scattering. The above anomalies observed in κ
l originate in the unique bonding mechanism (metavalent bonding), which suppresses the conventional reductive effect of mass to define κ
l. Our findings elucidate the distinct thermal transport properties of 2D materials and provide valuable insights for designing efficient thermoelectric materials.
AB - Exploring thermoelectric materials with captivating chemical bonding and low lattice thermal conductivity (κ
l) is crucial in thermoelectric research. Here, we propose two-dimensional (2D) γ-monochalcogenide (MX; M = Ge, Sn, Pb, and X = S, Se, Te) monolayers as potential thermoelectric materials. The exfoliation energies of γ-MX monolayers fall in the 12-16 meV/Å
2 range, less than graphene (21 meV/Å
2), suggesting their feasible realization through mechanical or chemical exfoliation. The electronic band structures exhibit an indirect band gap ranging from 0.41 eV for γ-PbTe to 0.86 eV for γ-PbS. The metavalent bonding in these monolayers results in an unusual trend in κ
l with atomic mass. Among studied monolayers, the γ-PbTe monolayer exhibits an ultralow room temperature κ
l of 0.49 W/mK, which accounts for its increased anharmonicity and higher scattering rates from acoustic and low-lying optical phonons. Despite having a higher mass than γ-PbS, γ-PbSe demonstrates enhanced κ
l values. Similar anomalous behavior is observed in the case of γ-GeTe (8.57 W/mK), γ-GeSe (3.10 W/mK), γ-SnTe (4.30 W/mK), and γ-SnSe (3.31 W/mK) monolayers. The enhanced κ
l in tellurides is attributed to the high bond stiffness, low charge transfer between M and X atoms, and widening of the phonon gap, which significantly reduces the phonon scattering. The above anomalies observed in κ
l originate in the unique bonding mechanism (metavalent bonding), which suppresses the conventional reductive effect of mass to define κ
l. Our findings elucidate the distinct thermal transport properties of 2D materials and provide valuable insights for designing efficient thermoelectric materials.
KW - 2D materials
KW - lattice thermal conductivity
KW - metavalent bonding
KW - monolayer chalcogenides
KW - phonon gap
UR - http://www.scopus.com/inward/record.url?scp=85170233521&partnerID=8YFLogxK
U2 - 10.1021/acsaem.3c01118
DO - 10.1021/acsaem.3c01118
M3 - Article
SN - 2574-0962
VL - 6
SP - 8787
EP - 8793
JO - ACS Applied Energy Materials
JF - ACS Applied Energy Materials
IS - 17
ER -