MoS₂-graphene heterostructures as efficient organic compounds sensing 2D materials

In this work, electrical properties and application for volatile organic compounds detection of molybdenum disulfide (MoS₂)−graphene (MS/G) heterostructure is investigated. The MS/G heterostructure is synthesized by physical stacking of single-layer (SL) MoS₂ over SL graphene. The difference in the work-functions between the MoS₂ and graphene leads to electron transfer from MoS₂ to graphene, which changes FET charge neutrality point (V_CNP) of graphene by as much as 30 V and increases the electron-to-hole ratio in graphene. This charge transport phenomenon is further confirmed by shifting of Raman G peak and quenching of photoluminescence intensity by 50% of MoS₂ in the heterostructure. Ultraviolet photoelectron spectroscopy reveals a 0.1 eV upshift of the Fermi level of graphene in MS/G, which is consistent with the electrical double-layer capacitance versus the electrode potential measurement and energy band alignment predicted by first-principle simulations. The heterogenity induced charge transfer in the heterostructure of MS/G results in outstanding performance in chemical sensing. The MS/G FET shows improved stability in dry air with negligible shifting of V_CNP, as compared to graphene FET. In the detection of toluene, the MS/G FET-based sensor shows higher sensitivity and superior signal-to-noise ratio compared to MoS₂ or graphene individually.