Orbitally driven low thermal conductivity of monolayer gallium nitride (GaN) with planar honeycomb structure: a comparative study.

Title Orbitally driven low thermal conductivity of monolayer gallium nitride (GaN) with planar honeycomb structure: a comparative study.
Authors Z. Qin; G. Qin; X. Zuo; Z. Xiong; M. Hu
Journal Nanoscale
DOI 10.1039/c7nr01271c

Two-dimensional (2D) materials with graphene as a representative have been intensively studied for a long time. Recently, monolayer gallium nitride (ML GaN) with honeycomb structure was successfully fabricated in experiments, generating enormous research interest for its promising applications in nano- and opto-electronics. Considering all these applications are inevitably involved with thermal transport, systematic investigation of the phonon transport properties of 2D GaN is in demand. In this paper, by solving the Boltzmann transport equation (BTE) based on first-principles calculations, we performed a comprehensive study of the phonon transport properties of ML GaN, with detailed comparison to bulk GaN, 2D graphene, silicene and ML BN with similar honeycomb structure. Considering the similar planar structure of ML GaN to graphene, it is quite intriguing to find that the thermal conductivity (?) of ML GaN (14.93 W mK(-1)) is more than two orders of magnitude lower than that of graphene and is even lower than that of silicene with a buckled structure. Systematic analysis is performed based on the study of the contribution from phonon branches, comparison among the mode level phonon group velocity and lifetime, the detailed process and channels of phonon-phonon scattering, and phonon anharmonicity with potential energy well. We found that, different from graphene and ML BN, the phonon-phonon scattering selection rule in 2D GaN is slightly broken by the lowered symmetry due to the large difference in the atomic radius and mass between Ga and N atoms. Further deep insight is gained from the electronic structure. Resulting from the special sp orbital hybridization mediated by the Ga-d orbital in ML GaN, the strongly polarized Ga-N bond, localized charge density, and its inhomogeneous distribution induce large phonon anharmonicity and lead to the intrinsic low ? of ML GaN. The orbitally driven low ? of ML GaN unraveled in this work would make 2D GaN prospective for applications in energy conversion such as thermoelectrics. Our study offers fundamental understanding of phonon transport in ML GaN within the framework of BTE and further electronic structure, which will enrich the studies of nanoscale phonon transport in 2D materials and shed light on further studies.

Citation Z. Qin; G. Qin; X. Zuo; Z. Xiong; M. Hu.Orbitally driven low thermal conductivity of monolayer gallium nitride (GaN) with planar honeycomb structure: a comparative study.. Nanoscale. 2017. doi:10.1039/c7nr01271c

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See more Gallium products. Gallium (atomic symbol: Ga, atomic number: 31) is a Block P, Group 13, Period 4 element with an atomic weight of 69.723.The number of electrons in each of Gallium's shells is 2, 8, 18, 3 and its electron configuration is [Ar] 3d10 4s2 4p1. The gallium atom has a radius of 122.1 pm and a Van der Waals radius of 187 pm. Gallium Bohr ModelGallium was predicted by Dmitri Mendeleev in 1871. It was first discovered and isolated by Lecoq de Boisbaudran in 1875. In its elemental form, gallium has a silvery appearance. Elemental GalliumGallium is one of three elements that occur naturally as a liquid at room temperature, the other two being mercury and cesium. Gallium does not exist as a free element in nature and is sourced commercially from bauxite and sphalerite. Currently, gallium is used in semiconductor devices for microelectronics and optics. The element name originates from the Latin word 'Gallia' referring to Gaul, the old name of France.


See more Nitrogen products. Nitrogen is a Block P, Group 15, Period 2 element. Its electron configuration is [He]2s22p3. Nitrogen is an odorless, tasteless, colorless and mostly inert gas. It is the seventh most abundant element in the universe and it constitutes 78.09% (by volume) of Earth's atmosphere. Nitrogen was discovered by Daniel Rutherford in 1772.

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