Monolayer-Mos2 Case Study

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Flexible nature and high surface-to-volume ratio makes monolayer-MoS2 a novel paradigm for tunable gas sensing devices. However, for further improvement in the performance of these devices, a new design strategy is essential to modulate the sensitivity of inert MoS2 basal plane. Here, we demonstrate from first-principles calculations that the gas adsorption properties of monolayer-MoS2 can be modulated through MoS antisite doping and strain. The antisite doped MoS defect with highly localized d-orbital electron density significantly promotes the electronic and catalytic properties through orbital hybridization, which leads to highly enhanced adsorption of NO, NO2, NH3, CO and CO2 gas molecules, in comparison to pristine MoS2. On application …show more content…
As one of the two-dimensional (2D) materials, m-MoS2 exhibits promising electronic properties such as high carrier mobilities (200 cm2V-1s-1) at room temperature, high current on/off ratio (1×108) and ultralow standby power dissipation [7,8]. Based on atomic layer MoS2, thin film transistors (TFT), optoelectronic devices and digital circuits have been successfully fabricated [9-11]. Besides, high surface-to-volume ratio, selective reactivity upon exposure to range of analytes, rapid response and recovery make MoS2 as a superior gas sensor with higher sensitivity and selectivity in comparison to graphene and other 2D materials [12-15]. It has been reported that the mechanically cleaved single and multilayer MoS2 based field effect transistors can be used as NO gas sensor with a detection limit of 0.8 ppm [16]. Flexible MoS2 TFT array on polyethylene terephthalate substrate shows high sensitivity towards NO2 sensing. In addition, functionalization of MoS2 with Pt nanoparticle was found to promote gas sensing activity three times higher with the detection limit of 2 ppb [17]. The MoS2 film synthesized by sulfurization of sputtered Mo-thin film was found to be useful for detection of NH3 in sub-ppm level [18]. Nevertheless, for further improvement in sensing capabilities, a new design …show more content…
In recent years, defect engineering has emerged as an effective strategy to tune various properties of 2D materials such as graphene, hexagonal boron nitride and silicene [19-21]. Like other 2D materials, intrinsic structural defects including point defects, grain boundaries, dislocations and edges can be realized in MoS2 either during the growth process [22, 23] or intentionally introduced through electron irradiation process [24], which are possible to modulate materials properties and also provide an opportunity to explore new functionality. For instance, the defects like VMoS6 vacancies are found to be highly reactive and could significantly promote the electronic and catalytic activity of the basal planes [26]. The S-vacancy is found to be the most preferred catalytic site for the adsorption of nonpolar gases like CO2 and CH4, in comparison to other stoichiometric sites [27]. On the other hand, monolayer MoS2 exhibits similar mechanical property to graphene, thus strain can serve as another means to modulate and optimize properties. For example, the application of biaxial strain to sulfur deficient MoS2 can inject spin moment [28]. The biaxial strain can effectively tailor the band gap of pristine MoS2 [29]. Also a combination of S-vacancy and strain can bring highest hydrogen evolution reaction activity in MoS2

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