Anisotropic in-plane thermal conductivity of black phosphorus nanoribbons at temperatures higher than 100 K

Abstract

Black phosphorus attracts enormous attention as a promising layered material for electronic, optoelectronic and thermoelectric applications. Here we report large anisotropy in in-plane thermal conductivity of single-crystal black phosphorus nanoribbons along the zigzag and armchair lattice directions at variable temperatures. Thermal conductivity measurements were carried out under the condition of steady-state longitudinal heat flow using suspended-pad micro-devices. We discovered increasing thermal conductivity anisotropy, up to a factor of two, with temperatures above 100 K. A size effect in thermal conductivity was also observed in which thinner nanoribbons show lower thermal conductivity. Analysed with the relaxation time approximation model using phonon dispersions obtained based on density function perturbation theory, the high anisotropy is attributed mainly to direction-dependent phonon dispersion and partially to phonon–phonon scattering. Our results revealing the intrinsic, orientation-dependent thermal conductivity of black phosphorus are useful for designing devices, as well as understanding fundamental physical properties of layered materials.

Variable range hopping electric and thermoelectric transport in anisotropic black phosphorus

“…Consistent with previous results, 14 these ribbons exhibit p-type conduction. The anisotropic ratio at room temperature is r AC /r ZZ $ 2.2 and S AC /S ZZ $ 1.3.…”

“…12,13 More interestingly, BP is a strongly anisotropic material even in the basal plane: the thermal conductivity is much higher along the zigzag than the armchair direction, while electrical conductivity shows the opposite anisotropy. 14 Choi et al 15 demonstrated that the variable range hopping (VRH) dominates electrical transport in thin BP flakes (10-30 nm thick). However, the BP flake crystal orientation was not specified in Choi and the coupling between the VRH process and the intrinsic anisotropy in BP is unclear.…”

Unraveling the Peculiarities in the Temperature-Dependent Structural Evolution of Black Phosphorus

“…In Figure 5b,c, we present respectively the thermal conductivity κ(Wm −1 ·K −1 ) and Hall coefficient R (cm 3 /Columb) of BP as functions of the temperature in the range of 85 K to 320 K. Until 210 K, the Hall coefficient showed a steep increase; however, below 210 K, there was a change in the rate (note the y-axis is in logarithmic scale). Recently, the thermal conductivity of BP nanoflakes was careful studied by Lee et al [23]. The thermal conductivity reported for these nanoflakes also showed a distinct change in this temperature range.…”

“…In particular, below 200 K, there is a distinct change in the temperature dependence. Several macroscopic properties of black phosphorus (BP), such as the Hall coefficient, thermal conductivity, etc., show a nonlinear temperature dependence [22,23]. Indeed, interesting temperature-dependent changes in some of these macroscopic properties make BP an ideal candidate for several potential practical applications [24,25].…”

Emerging Trends in Phosphorene Fabrication towards Next Generation Devices

“…BP single crystals larger than 1 cm were crystallized in the form of flakes at the cold end of the ampoule. The low‐pressure route, with the use of a mineralizer as the reaction promoter, was of interest because of its high yield in non‐toxic experimental conditions 112, 113, 114, 121, 122, 123. The red phosphorus, converted to BP by SnI 4 mineralization, gives red phosphorus and Au as its byproducts 113, 124…”