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

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.