Current Enhancement and Bipolar Current Modulation of Top-Gate Transistors Based on Monolayer MoS2 on Three-Layer WxMo1–xS2

We demonstrated the top-gate transistors composed of monolayer MoS2 grown on three-layer alloys MoxW1–xS2 prepared by sequential sulfurization of predeposited transition metal films. The elemental mapping of the alloy indicates a uniform distribution of both cations Mo and W in the grown samples. Surprisingly, we find that the drain current of transistors could be enhanced by 2 orders of magnitude as the composition of Mo increases, whereas the gate-controlled current modulation turns bipolar and ultimately vanishes. These features might originate from the formation of in-gap defect states, with modest activation energy for transport and moderate hopping probability for current conduction, or a reduced electronic band gap of the conducting channel because of strain.