Thermal transport across Twin Grain Boundaries in Polycrystalline Graphene from Nonequilibrium Molecular Dynamics Simulations

We have studied the thermal conductance of tilt grain boundaries in graphene using nonequilibrium molecular dynamics simulations. When a constant heat flux is allowed to flow, we observe sharp jumps in temperature at the boundaries, characteristic of interfaces between materials of differing thermal properties. On the basis of the magnitude of these jumps, we have computed the boundary conductance of twin grain boundaries as a function of their misorientation angles. We find the boundary conductance to be in the range 1.5 x 10(10) to 4.5 x 10(10) W/(m(2) K), which is significantly higher than that of any other thermoelectric interfaces reported in the literature. Using the computed values of boundary conductances, we have identified a critical grain size of 0.1 mu m below which the contribution of the tilt boundaries to the conductivity becomes comparable to that of the contribution from the grains themselves. Experiments to test the predictions of our simulations are proposed.