Characterization of anisotropic thermal conductivity of suspended nm-thick black phosphorus with frequency-resolved Raman spectroscopy

Frequency-resolved Raman spectroscopy (FR-Raman) is a new technique for nondestructive thermal characterization. Here, we apply this new technique to measure the anisotropic thermal conductivity of suspended nm-thick black phosphorus samples without the need of optical absorption and temperature coefficient. Four samples with thicknesses between 99.8 and 157.6 nm are studied. Based on steady state laser heating and Raman measurement of samples with a specifically designed thermal transport path, the thermal conductivity ratio (K-ZZ/K-AC) is determined to be 1.86-3.06. Based on the FR-Raman measurements. the armchair thermal conductivity is measured as 14-22 W m(-1) K-1, while the zigzag thermal conductivity is 40-63 W m(-1) K-1. FR-Raman has great potential for studying the thermal properties of various nanomaterials. This study significantly advances our understanding of thermal transport in black phosphorus and facilitates the application of black phosphorus in novel devices. Published by AIP Publishing.