Enhancing thermal transport across diamond/graphene heterostructure interface

The thermal properties of two-dimensional materials and their heterostructure are critical for efficient heat dissipation in nano-devices. A good example is graphene which exhibits excellent in-plane thermal transport properties. However, the substantial interfacial thermal resistance between graphene and the substrate greatly hinders its practical application. Diamond is a good choice as a substrate to reduce out-of-plane phonon scattering when graphene is contacted with the substrate because of their high structural similarity. Based on non-equilibrium molecular dynamics simulations, the effects of graphene layer count and the temperature on the thermal conductance of diamond/graphene heterostructure are investigated. The results show that the interfacial thermal conductance of diamond/single-layer graphene heterostructure is at least double that of diamond/multi-layer graphene heterostructure. Moreover, high temperature is also conducive to thermal transport for diamond/graphene heterostructure. Due to the anisotropy of graphene, the in-plane and out-of-plane phonon density of state were analyzed. The trend of overlap energy of out-of-plane phonon density of state is consistent with that of the interfacial thermal conductance, which suggests that out-of-plane phonon has a greater effect on heat transport at the interface. The increasing temperature excites more high-frequency phonons, and thus, promotes the phonon coupling of diamond and graphene. This well explains the increases in interfacial thermal conductance at a higher temperature.