Thermal Transport in Supported Graphene: Substrate Effects on Collective Excitations

A detailed computational analysis of thermal transport in supported graphene reveals the possibility of tuning its thermal conductivity by targeted chemical modifications of the substrate's surface. Based on classical molecular dynamics with an accurate charge-optimized bond-order force field and a time-domain normal-mode analysis, our approach allows us to distinguish collective from single-phonon excitations. The computations reveal a disproportional reduction of the thermal conductivity, due to the two different excitations, when graphene interacts with a substrate. Deposition of graphene on a bare silica surface leads to a dramatic reduction of the thermal conductivity and a change in the heat transport mechanism. Remarkably, partial hydroxylation of the silica surface almost doubles the thermal conductivity of the collective excitations. Thus, specific surface terminations allow for control of the thermal conductivity of graphene.