Towards intrinsic MoS2 devices for high performance arsenite sensing

Molybdenum disulphide (MoS2) is one of the most attractive two dimensional materials other than graphene, and the exceptional properties make it a promising candidate for bio/chemical sensing. Nevertheless, intrinsic properties and sensing performances of MoS2 are easily masked by the presence of the Schottky barrier (SB) at source/drain electrodes, and its impact on MoS2 sensors remains unclear. Here, we systematically investigated the influence of the SB on MoS2 sensors, revealing the sensing mechanism of intrinsic MoS2. By utilizing a small work function metal, Ti, to reduce the SB, excellent electrical properties of this 2D material were yielded with 2-3 times enhanced sensitivity. We experimentally demonstrated that the sensitivity of MoS2 is superior to that of graphene. Intrinsic MoS2 was able to realize rapid detection of arsenite down to 0.1 ppb without the influence of large SB, which is two-fold lower than the World Health Organization (WHO) tolerance level and better than the detection limit of recently reported arsenite sensors. Additionally, accurately discriminating target molecules is a great challenge for sensors based on 2D materials. This work demonstrates MoS2 sensors encapsulated with ionophore film which only allows certain types of molecules to selectively permeate through it. As a result, multiplex ion detection with superb selectivity was realized. Our results show prominent advantages of intrinsic MoS2 as a sensing material. (C) 2016 Author(s).