Photothermal electric effect of multilayer MoS2-graphene heterojunction

Due to the exceptional electrical and optical properties of graphene, public interest has grown rapidly since the material was exfoliated onto SiO2 in 2004 [1-3]. Other two dimensional (2D) crystal materials such as MoS₂, hBN, and WSe₂, individually or in combination with graphene, also have shown intriguing properties. One of the interesting applications is using the 2D heterojunction as a photodetector. There have been literatures reported on graphene-MoS₂ heterojunction photodetectors, claiming the photoresponse mechanism as a photovoltaic effect (PV), which is due to the separation of electron-hole pairs created in MoS₂ at less than 700 nm wavelengths [4, 5]. In this paper, we report photothermal electric effect (PTE) of a multilayer MoS₂-graphene heterojunction photodetector based on the large differences of Seebeck coefficients between MoS₂ (-700 μV/K) [6] and graphene (-50 μV/K) [7].