Edge effect on phonon transport in suspended and supported graphene nanoribbons

Heat conduction in a graphene nanoribbon (GNR) is investigated using nonequilibrium molecular dynamics simulation. GNR shows an intriguing dependence of thermal conductivity on its width, length, and edge shape. For example, thermal conductivity of thin armchair GNR is about three times lower than that of zigzag GNR due to the strong phonon scattering at the armchair edge. The substrate interaction is another critical issue for phonon transport. GNR supported on a substrate is analyzed by using the Lennard-Jones potential, and the thermal conductivity of a zigzag ribbon is found to decrease significantly due to phonon scattering by the substrate. However, under the same conditions, that of armchair ribbon is not affected by the substrate or even increases. This phenomenon is caused by the suppression of edge-localized flexural phonons of armchair GNR, which triggers their smaller thermal conductivity than the zigzag one. This anomalous edge-substrate combined effect on thermal transport in supported GNR is discussed.