Investigation for Thermoelectric Properties of the MoS₂ Monolayer–Graphene Heterostructure: Density Functional Theory Calculations and Electrical Transport Measurements

We investigated the thermoelectric (TE) properties of the MoS₂ monolayer–graphene heterostructure which consists of the MoS₂ monolayer and graphene. The electronic structures of the MoS₂ monolayer–graphene heterostructure are mainly contributed from graphene and the MoS₂ monolayer for the valence band maximum and conduction band minimum, respectively. The change in the electronic structures near the Fermi level is responsible for the fact that the calculated Seebeck coefficients S and electrical conductivity σ/τ of MoS₂ monolayer–graphene are largely affected from those of graphene and the MoS₂ monolayer. Its power factor S²σ/τ is increased compared to those of graphene and the MoS₂ monolayer at an electron concentration of 10¹¹ to 10¹² cm^–2, which corresponds to a three-dimensional concentration of 3 × 10¹⁸ to 3 × 10¹⁹ cm^–3. We also demonstrated that the MoS₂ monolayer shows the p-type TE behavior, while the MoS₂ monolayer–graphene heterostructure is given to the n-type TE material. The current study provides a strategy to improve TE properties of the MoS₂ monolayer through the formation of the MoS₂ monolayer–graphene heterostructure.