Measurement of specific heat and thermal conductivity of supported and suspended graphene by a comprehensive Raman optothermal method

Abstract

The last decade has seen the rapid growth of research on two-dimensional (2D) materials, represented by graphene, but research on their thermophysical properties is still far from sufficient owing to the experimental challenges. Herein, we report the first measurement of the specific heat of multilayer and monolayer graphene in both supported and suspended geometries. Their thermal conductivities were also simultaneously measured using a comprehensive Raman optothermal method without needing to know the laser absorption. Both continuous-wave (CW) and pulsed lasers were used to heat the samples, based on consideration of the variable laser spot radius and pulse duration as well as the heat conduction within the substrate. The error from the laser absorption was eliminated by comparing the Raman-measured temperature rises for different spot radii and pulse durations. The thermal conductivity and specific heat were extracted by analytically fitting the temperature rise ratios as a function of spot size and pulse duration, respectively. The measured specific heat was about 700 J (kg K)⁻¹ at room temperature, which is in accordance with theoretical predictions, and the measured thermal conductivities were in the range of 0.84–1.5 × 10³ W (m K)⁻¹. The measurement method demonstrated here can be used to investigate in situ and comprehensively the thermophysical properties of many other emerging 2D materials.