▎ 摘　　要

Grain size and thermal coupling to the substrate are among the major effects that may substantially dominate the heat transport properties of graphene-based nanodevices. In this study, we performed extensive transient molecular dynamics (MD) simulations on the basis of pump-probe technique to calculate the thermal boundary resistance (Kapitza resistance) between polycrystalline graphene and the silica substrate. As a remarkable finding, our results reveal that the thermal boundary resistance can be suppressed by decreasing of the grain size, so that the maximum thermal boundary resistance was predicted for the monocrystalline graphene. It was moreover observed that the thermal boundary resistance is less sensitive to the temperature variations for the polycrystalline graphene with smaller grain sizes. The obtained results and the corresponding underlying mechanisms were discussed by analyzing the roughness of polycrystalline graphene samples as well as the vibrational density of states. Considering the dominant role that the thermal boundary resistance plays in the nanoscale heat transfer, the findings of this paper may provide useful vision in heat management of graphene-based nanodevices.