Thermal Transport across hBN/Graphene Interfaces*

Heterostructures of two-dimensional materials (2D) are a promising platform for the observation of phonon interface transport and coherent-phonon effects. Layer thickness and orientation can be tuned during heterostructure fabrication which provides a variety of ways to control the thermal-transport properties of the system. Using the 3ω method, we measure the interfacial thermal resistance between two common 2D materials, hexagonal boron nitride (hBN) and graphene (Gr), to be significantly lower than previously reported Raman thermometry values. The uncertainty of our measurement is limited by the uncertainty in the literature value for the bulk thermal conductivity of hBN. We aim to provide a precise measurement of the cross plane thermal resistance of hBN flakes from the bulk-like down to the ballistic phonon transport regime and demonstrate that a variety of geometries of 3ω wires including a semicircle with 750μm diameter, measure the same cross plane thermal resistance of a 70nm thick SiO₂ film with a standard deviation of 4.7 m² K GW^-1.