First-principles study of thermal properties of borophene

Phys. Chem. Chem. Phys.

Gao

et al. 2017

Borophene (boron sheet) as a new type of two-dimensional (2D) material was grown successfully recently. Unfortunately, the structural stability of freestanding borophene is still an open issue. Theoretical research has found that full hydrogenation can remove such instability, and the product is called borophane. In this paper, using first-principles calculations we investigate the lattice dynamics and thermal transport properties of borophane. The intrinsic lattice thermal conductivity and the relaxation time of borophane are investigated by solving the phonon Boltzmann transport equation (BTE) based on first-principles calculations. We find that the intrinsic lattice thermal conductivity of borophane is anisotropic, as the higher value (along the zigzag direction) is about two times of the lower one (along the armchair direction). The contributions of phonon branches to the lattice thermal conductivities along different directions are evaluated. It is found that both the anisotropy of thermal conductivity and the different phonon branches which dominate the thermal transport along different directions are decided by the group velocity and the relaxation time of phonons with very low frequency. In addition, the size dependence of thermal conductivity is investigated using cumulative thermal conductivity. The underlying physical mechanisms of these unique properties are also discussed in this paper.

Section: Introductionmentioning

confidence: 99%

Anisotropic intrinsic lattice thermal conductivity of borophane from first-principles calculations

Liu

Phys. Chem. Chem. Phys.

Gao

et al. 2017

“…The superconducting transition temperature T c of borophene is about 19 K, which can be increased to 27.4 K by applying a tensile strain, or 34.8 K by hole doping 9 . Due to the strong phonon-phonon scattering, the lattice thermal conductivity of borophene is unexpectedly low 20 . Recently, Feng et al synthesized two boron sheets: β 12 and χ 3 , both of which belong to the triangular lattice but differ in arrangements of periodic holes 21 .…”

Section: Introductionmentioning

confidence: 99%

High anisotropy of fully hydrogenated borophene

Lü

Phys. Chem. Chem. Phys.

et al. 2016

113

We have studied the mechanical properties and phonon dispersions of fully hydrogenated borophene (borophane) under strains by first principles calculations. Uniaxial tensile strains along the a-and b-direction, respectively, and biaxial tensile strain have been considered. Our results show that the mechanical properties and phonon stability of borophane are both highly anisotropic. The ultimate tensile strain along the a-direction is only 0.12, but it can be as large as 0.30 along the b-direction. Compared to borophene and other 2D materials (graphene, graphane, silicene, silicane, h-BN, phosphorene and MoS 2 ), borophane presents the most remarkable anisotropy in inplane ultimate strain, which is very important for strain engineering. Furthermore, the phonon dispersions under the three applied strains indicate that borophane can withstand up to 5% and 15% uniaxial tensile strain along the a-and b-direction, respectively, and 9% biaxial tensile strain, indicating that mechanical failure in borophane is likely to originate from phonon instability.

“…36 Undoubtedly, the experimental realization of borophene raises the hope that it might serve as a high-speed pathway for phonon transport, due to its short covalent bonds and light atomic mass. Although the thermal conductivity 37,38 and thermal conductance 39 of borophene have been explored, the ballistic phonon transport mechanisms and properties of borophene are still largely unknown, and thus a solid understanding is needed in order to provide guidance for the exploration of its applications.…”

Section: Introductionmentioning

confidence: 99%

Superior lattice thermal conductance of single-layer borophene

et al. 2017

By way of the non-equilibrium Green's function simulations and first-principles calculations, we report that borophene, a single layer of boron atoms that was fabricated recently, possesses an extraordinarily high lattice thermal conductance in the ballistic transport regime, which even exceeds graphene. In addition to the obvious reasons of light mass and strong bonding of boron atoms, the superior thermal conductance is mainly rooted in its strong structural anisotropy and unusual phonon transmission. For low-frequency phonons, the phonon transmission within borophene is nearly isotropic, similar to that of graphene. For highfrequency phonons, however, the transmission is one-dimensional, that is, all the phonons travel in one direction, giving rise to its ultra-high thermal conductance. The present study suggests that borophene is promising for applications in efficient heat dissipation and thermal management, and also an ideal material for revealing fundamentals of dimensionality effect on phonon transport in ballistic regime.