Interfacial Thermal Contact Conductance inside the Graphene–Bi₂Te₃ Heterostructure

Graphene–Bi₂Te₃, a graphene-based compound with a metal/metalloid heterostructure, is recently discovered to be a potentially novel thermoelectric material, demonstrating unprecedently enhanced thermoelectric efficiencies. The interfacial thermal transport must play an important role in determining the thermoelectric performance of this heterostructure. In particular, the interfacial thermal contact conductance (G_c) must be known in order to correctly elaborate the thermoelectric performances of graphene–Bi₂Te₃. Furthermore, the large nonlinear optoelectric response of this heterostructure redefines both the graphene thermal conductivity (k_g) and its optical absorbance (A_g). A significantly suppressed A_g is predicted as low as 0.86% from its nominal value of 2.72% when suspended, from the transfer matrix calculations based on the Fresnel principle. Both G_c and k_g are simultaneously determined from the optothermal Raman thermometry by duplexing the Raman data sets using two different objective magnifications (20× and 100×), which allows for the matching of the number of unknowns (G_c and k_g) with the corresponding two Raman data sets. The thermal properties of G_c and k_g for the graphene–Bi₂Te₃ heterostructure are first determined as 3.455 ± 0.619 × 10⁶ W m⁻² K⁻¹ and 440.124 ± 76.265 W m⁻¹ K⁻¹, respectively.