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

Abstract

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.

2D Boron Sheets: Structure, Growth, and Electronic and Thermal Transport Properties

“…It was found that the number of layers had almost no effect on the lattice thermal conductivity of borophene, which was attributed to the negligible effect of interlayer vdW interactions of the multilayer structure. This is similar to black phosphorene and MoS 2 , while it is different from that of graphene with monotonically decreasing of thermal conductivity with the increasing number of layers …”

“…It was explained by the fact that the relaxation time of acoustic branches for C‐borophane is 10 3 −10 4 ps, two order of magnitudes larger than that of δ 6 borophene. Comparing with stanene and arsenene, the thermal transfer of C‐borophane is obviously faster due to higher group velocity although they possess the same order of phonon relaxation time . On the other hand, the thermal conductivity of hydrogenated graphene‐like borophene along armchair and zigzag directions is 293 and 335 W m −1 K −1 , respectively, which is the largest value among all reported 2D borophene sheets to date.…”

“…The calculated thermal conductivities of borophene, BNRs and BNTs are summarized in Table 1 . Although the lattice thermal conductivity of borophene is about two orders lower than that of graphene, it is still larger than silicene (5–65 W m −1 K −1 ), stanene (11.6 W m −1 K −1 ), and arsenene (7.8 W m −1 K −1 ) in the armchair direction, 30.4 W m −1 K −1 in the zigzag direction . Mingo and co‐workers presented a quadratic dispersion for the lowest branch in the buckled 8‐Pmmn borophene through a reformulation of the IFCs in terms of internal coordinates .…”

Edge-Dependent Electronic and Magnetic Characteristics of Freestanding β 12-Borophene Nanoribbons

“…The mechanical properties of several borophene sheets have been investigated, and their ideal strength, ultimate strain, and Young’s modulus have been reported [ 16 , 18 – 22 ]. Superconductivity [ 23 – 27 ] and thermal conductivity [ 13 , 28 ] of borophene sheets have also been studied. It was predicted that their superconductivity could be modulated by the strain, while their thermal conductivity is low.…”

Stabilization and Metallic to Semiconducting Transition in 2D Boron Sheet

“…Strain and surface functionalization have been proved to be effective on stabilizing the 2D materials. [15][16][17][18][19][20] Penev et al proposed that the imaginary frequencies of both β 12 and χ 3 borophene near the G point may be eliminated by applying a uniform tensile strain. 15 Additional, based on the first-principles calculations, 19,20 Xu et al and Liu et al predict that the fully hydrogenated buckled triangular borophene is dynamical stable without imaginary frequency.…”