Thermal conductivity of single layer graphene
31 Jul 2014. NUS scientists have demonstrated that thermal conductivity of suspended single layer graphene increases as length increases.
It is well known that any bulk material has a finite thermal conductivity. For example, at room temperature, copper has a thermal conductivity of 385 Wm-1K-1, whereas polyethylene is a thermal insulator with thermal conductivity about 1000 times smaller, 0.4 Wm-1K-1. However, the thermal conductivity of nanoscale structures might not have a definite value. It depends on its geometry, size and material composite.
Statistical mechanics and computer simulation on heat transfer in low-dimensional systems, such as one-dimensional (1D) or two-dimensional (2D) systems, suggests that the thermal conductivity due to phonons increases as the length of the system increases. It increases as a power law in 1D systems, like nanotubes and nanowires, and increases logarithmically with length in 2D systems (see Figure). Scientists from UC Berkeley have experimentally verified this theoretical predication in 1D systems by using carbon nanotubes and boron nitride nanotubes in 2008.
Recently, a team led by Professor Baowen LI and Professor Barbaros ÖZYILMAZ from the Department of Physics, NUS, has demonstrated experimentally for the first time the logarithmic length dependence of thermal conductivity of suspended single layer graphene. The computational work is led by Dr Davide DONADIO at Max-Planck Institute for Polymer Research. The results from this study supports the experimental conclusions. This joint work has been published in Nature Communications.
This research has revealed a new phonon transport mechanism in low-dimensional systems and opened the door for new research in 2D systems.
Figure: Logarithmic length dependence of the thermal conductivity of suspended single layer graphene; experiment (left) and computer simulation (right). [Picture credit: Nature Communications]
X Xu, Luiz FCP, Y Wang, J Wu, K Zhang, X Zhao, S Bae, Cong TB, R Xie, JTL Thong, BH Hong, KP Loh, D Donadio, B Li, B Özyilmaz. “Length-dependent thermal conductivity in suspended single-layer graphene” Nature Comms 5 (2014) 3689.