Gas Sensing Properties of Graphene/MoS₂/Graphene Lateral Heterostructure: A First Principles Investigation

2-D materials are promising candidates for gas sensing applications due to their high surface to volume ratio. However, graphene and MoS2, two prominent members of these materials, show little sensitivity toward gas molecules such as NH3, CO2, and H2O. In this work, the gas sensing properties of graphene and MoS2 lateral heterostructures are investigated theoretically using density functional theory (DFT) in combination with a non-equilibrium Green’s function (NEGF) formalism. The heterostructure consists of a MoS2 part, which is sandwiched between two graphene sides. There are distinct interfaces between MoS2 and graphene, whereby C-Mo and C-S bonds connect the two materials. The results reveal that CO2 and H2O are weakly adsorbed on different parts of the heterostructure, while NH3 molecules are strongly adsorbed on the C-Mo interface with an energy equal to −1.233 eV. Further analyses reveal that only the adsorbed NH3 at the C-Mo surface leads to significant changes in the electronic structure, even in an atmospheric environment, where O2 molecules are pre-adsorbed at the interface. The planar average of electrostatic potential and the calculated currents at ±0.5 V applied voltages reveal that the Schottky barrier at C−Mo graphene/MoS2 interface is very sensitive to the adsorption of NH3 gas molecule.