Abstract
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.
Highlights
VDS NWhere A is the contact area of the MoS2-metal junction, AÃ2D is the two dimensional equivalent Richardson constant, T is the absolute temperature, q is the electron charge, kB is the Boltzmann constant, and N is the ideality factor; the Schottky barrier (SB) significantly reduces IDS and increases contact resistance
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
Intrinsic properties and sensing performances of MoS2 are masked by the presence of the Schottky barrier (SB) at source/drain electrodes, and its impact on MoS2 sensors remains unclear
Summary
Where A is the contact area of the MoS2-metal junction, AÃ2D is the two dimensional equivalent Richardson constant, T is the absolute temperature, q is the electron charge, kB is the Boltzmann constant, and N is the ideality factor; the SB significantly reduces IDS and increases contact resistance. IDS versus VGS characteristics were measured after introduction of buffer solution with different AsO2– ion concentrations ranging from 0 to 100 000 ppb, as shown in Fig. 3(a) (Ti contacts, VDS 1⁄4 0.03 V). Pt-contact FETs illustrated a falling of IDS when the AsO2– concentration increased from 0 to 100 000 ppb (Fig. 3(b)). The curve of the MoS2 FET sensor (Ti contact, VGS 1⁄4 0 V) showed clear steps after introduction of solutions with different AsO2– ion concentrations (black curve). 3. (a) IDS vs VGS curves of Ti-contact MoS2 with different AsO2À concentrations. (b) IDS vs VGS curves of the Pt-contact MoS2 device with different AsO2À concentrations. (f) Output signal of MoS2 devices with Ti electrodes is larger than 3 times the deviation of its noise, indicating that the sensors are able to detect AsO2À down to 0.1 ppb.
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