Layer-Dependent NO₂-Sensing Performance in MoS₂ for Room-Temperature Monitoring

Few-layer MoS 2 with exceptional physical and chemical properties has attracted notable attention for next-generation gas sensors. The layer-dependent sensing performance for detecting NO 2 based on MoS 2 is not fully understood. Here, we report the direct synthesis of high-crystallinity uniform few-layer MoS 2 via chemical vapor deposition. The influence of layer thickness on the NO 2 -sensing performance is evaluated. We show that, as compared to the monolayer and trilayer counterparts, the bilayer MoS 2 presents the best sensitivity at room temperature. Further density functional theory calculations reveal that the bilayer MoS 2 with an AA stacking sequence is more favorable for the physisorption of NO 2 molecules due to the more negative adsorption energy, facilitating charge transfer during the NO 2 adsorption and thus increasing the electrical response of the gas sensors. This work provides a basic understanding of layer-dependent gas-sensing performance and serves as a reference for designing room-temperature gas sensors for low power consumption and reliable responsivity.