Electrical characterization of back-gated bi-layer MoS 2 field-effect transistors and the effect of ambient on their performances

Two-dimensional transition-metal dichalcogenides such as MoS 2 are promising channel materials for transistor scaling. Here, we report the performance and environmental effects on back-gated bi-layer MoS 2 field-effect transistors. The devices exhibit Ohmic contacts with titanium at room temperature, on/off ratio higher than 10 7 , and current saturation. Furthermore, we show that the devices are sensitive to oxygen and water in the ambient. Exposure to ambient dramatically reduces the on-state current by up to 2 orders of magnitude likely due to additional scattering centers from chemisorption on the defect sites of MoS 2 . We demonstrate that vacuum annealing can effectively remove the absorbates and reversibly recover the device performances. This method significantly reduces the large variations in MoS 2 device caused by extrinsic factors.