The role of flexural coupling in heat dissipation from a two-dimensional layered material to its hexagonal boron nitride substrate
Understanding the limits of phononic heat dissipation from a two-dimensional layered material (2DLM) to its hexagonal boron nitride (h-BN) substrate and how it varies with the structure of the 2DLM is important for the design and thermal management of h-BN-supported nanoelectronic devices. We formulate an elasticity-based theory to model the phonon-mediated heat dissipation between a 2DLM and its h-BN substrate. By treating the h-BN substrate as a semi-infinite stack of harmonically coupled thin plates, we obtain semi-analytical expressions for the thermal boundary conductance (TBC) and interfacial phonon transmission spectrum. We evaluate the temperature-dependent TBC of the $N$-layer 2DLM (graphene or MoS$_{2}$) on different common substrates (h-BN vs. a-SiO$_{2}$) at different values of $N$. The results suggest that h-BN is substantially more effective for heat dissipation from MoS$_{2}$ than a-SiO$_{2}$ especially at large $N$. To understand the limitations of the our stack model, we also compare its predictions in the $N=\infty$ limit to those of the more exact Atomistic Green's Function model for the graphite-BN and molybdenite-BN interfaces. Our stack model provides clear insights into the key role of the flexural modes in the TBC and how the anisotropic elastic properties of h-BN affect heat dissipation.