Thermal Transport in Suspended and Supported Few-Layer Graphene

We report thermal conductivity (kappa) measurements from 77 to 350 K on both suspended and supported few-layer graphene using a thermal-bridge configuration. The room temperature value of kappa is comparable to that of bulk graphite for the largest flake, but reduces significantly for smaller flakes. The presence of a substrate lowers the value of kappa, but the effect diminishes for the thermal transport in the top layers away from the substrate. For the suspended sample, the temperature dependence of kappa follows a power law with an exponent of 1.4 +/- 0.1, suggesting that the flexural phonon modes contribute significantly to the thermal transport of the suspended graphene. The measured values of kappa are generally lower than those from theoretical studies. We attribute this deviation to the phonon-boundary scattering at the graphene-contact interfaces, which is shown to significantly reduce the apparent measured thermal conductance of graphene.