RESUMO
Black phosphorus has been revisited recently as a new two-dimensional material showing potential applications in electronics and optoelectronics. Here we report the anisotropic in-plane thermal conductivity of suspended few-layer black phosphorus measured by micro-Raman spectroscopy. The armchair and zigzag thermal conductivities are â¼20 and â¼40 W m(-1) K(-1) for black phosphorus films thicker than 15 nm, respectively, and decrease to â¼10 and â¼20 W m(-1) K(-1) as the film thickness is reduced, exhibiting significant anisotropy. The thermal conductivity anisotropic ratio is found to be â¼2 for thick black phosphorus films and drops to â¼1.5 for the thinnest 9.5-nm-thick film. Theoretical modelling reveals that the observed anisotropy is primarily related to the anisotropic phonon dispersion, whereas the intrinsic phonon scattering rates are found to be similar along the armchair and zigzag directions. Surface scattering in the black phosphorus films is shown to strongly suppress the contribution of long mean-free-path acoustic phonons.