Carrier Transport Properties of MoS₂ Asymmetric Gas Sensor Under Charge Transfer-Based Barrier Modulation

Over the past few years, two-dimensional materials have gained immense attention for next-generation electric sensing devices because of their unique properties. Here, we report the carrier transport properties of MoS₂ Schottky diodes under ambient as well as gas exposure conditions. MoS₂ field-effect transistors (FETs) were fabricated using Pt and Al electrodes. The work function of Pt is higher than that of MoS_2, while that of Al is lower than that of MoS₂. The MoS₂ device with Al contacts showed much higher current than that with Pt contacts because of its lower Schottky barrier height (SBH). The electrical characteristics and gas responses of the MoS₂ Schottky diodes with Al and Pt contacts were measured electrically and were simulated by density functional theory calculations. The theoretically calculated SBH of the diode (under gas absorption) showed that NO_x molecules had strong interaction with the diode and induced a negative charge transfer. However, an opposite trend was observed in the case of NH₃ molecules. We also investigated the effect of metal contacts on the gas sensing performance of MoS₂ FETs both experimentally and theoretically.