MoS₂-Based Optoelectronic Gas Sensor with Sub-parts-per-billion Limit of NO₂ Gas Detection

Abstract

Red light illumination with photon energy matching the direct band gap of chemical vapor deposition grown single-layer MoS2 with Au metal electrodes was used to induce a photocurrent which was employed instead of dark current for NO2 gas sensing. The resulting Au/MoS2/Au optoelectronic gas sensor showed a significant enhancement of the device sensitivity S toward ppb level of NO2 gas exposure reaching S = 4.9%/ppb (4900%/ppm), where S is a slope of dependence of relative change of the sensor resistance on NO2 concentration. Further optimization of the MoS2-based optoelectronic gas sensor by using graphene (Gr) with a work function lower than that of Au for the electrical contacts to the MoS2 channel allowed an increase of photocurrent. The limit of detection of NO2 gas at the level of 0.1 ppb was obtained for the MoS2 channel with graphene electrodes coated by Au. This value was calculated using experimentally obtained sensitivity and noise values and exceeds the U.S. Environment Protection Agency requirement for NO2 gas detection at ppb level.

Caveats in obtaining high-quality 2D materials and property characterization

“…This peak position change is greater than that between MoS 2 flakes with thicknesses of 1.3 and 7.6 nm, as shown in Fig. 3(f) [44]. This "breath" experiment highlights the importance of understanding sample history and the environmental considerations when utilizing PL for quantification of layer thickness.…”

“…Most research-grade Raman spectrometers match these conditions for MoS 2 , which has an indirect band gap of ;1.3 eV in bulk and a direct band gap of ;1.8 eV at monolayer thickness. Therefore, the PL peak position of MoS 2 may be used as an additional indication of the layer number [44]. However, the PL response of the monolayer material is so sensitive that the peak rapidly and dynamically evolves in response to the environment-even when one merely breathes onto the sample (Fig.…”

MoS2 Nanosheets Sensitized with Quantum Dots for Room-Temperature Gas Sensors

“…As an alternative strategy, UV light irradiation or gate effect was employed to improve sensitivity toward NO 2 of MoS 2 sensor [18][19][20][21]. Pham et al [18] employed LED illumination to improve sensitivity of CVD grown single-layer MoS 2 , achieving sub-ppb limit of NO 2 gas detection. However, the comparatively high sensitivity and fast response/recovery kinetics at room temperature were not simultaneously obtained for pristine MoS 2 gas sensors.…”

Non-Carbon 2D Materials-Based Field-Effect Transistor Biosensors: Recent Advances, Challenges, and Future Perspectives

“…Bulk materials, such as gas-sensitive metal oxides and polymer membranes, were used as the first channel materials in FET chemical sensors. However, the unfavored electronic properties and limited interaction between target molecules and bulky materials limited their use, especially as they sometimes require specific operating conditions, such as high temperature for gas sensing [ 2 , 3 , 4 ].…”