Substrate effects on the near-field radiative heat transfer between bi-planar graphene/hBN heterostructures

The hybridization of surface plasmon polaritons and hyperbolic phonon polaritons in graphene/hBN heterostructures has been well documented to achieve very high radiative heat flux transferred in the near field, paving the way for wide applications ranging from energy harvesting, non-contact thermal management to thermal imaging. However, previous related theoretical studies mainly focused on suspended structures. When it comes to the experimental implementation, a supporting substrate is quite a necessity for this kind of 2D layered heterostructures to ensure structural stability. Herein, the near-field radiative heat transfer (NFRHT) between bi-planar graphene/hBN heterostructures was revisited by integrating them with various substrates, including Au, SiC, and silica, under the framework of the fluctuation-dissipation theorem. The results show that each substrate exerts significant impacts either further enhancing or suppressing the NFRHT between those bi-planar heterostructures, due to the competition between polaritonic couplings and dielectric losses. Whereas, these substrate effects depend on the hBN thickness with a critical length, beyond which the hBN itself is thick enough to indiscriminately screen all these effects. The findings in this study will be instructive to both the experimental designs and device integrations for graphene-based NFRHT applications.