MoS₂ Decorated α-Fe₂O₃ Nanostructures for Efficient NO₂ Gas Sensor

Over the past few decades, metal oxide-based thin-film sensors have been widely studied and commercialized for gas sensing applications, but their poor sensing response and high-temperature operation (300 °C) are the issues to be addressed. Here, we demonstrate the molybdenum disulfide (MoS2) decorated $\alpha $ -Fe2O3 thin-film-based NO2 gas sensor. The $\alpha $ -Fe2O3 thin film was deposited on silicon substrate using the RF magnetron sputtering technique at 600 °C substrate temperature. The $\alpha $ -Fe2O3 thin films were characterized using an X-ray diffractometer and a scanning electron microscope for structural and morphological characterizations. Furthermore, we decorated the Fe2O3 thin film using hydrothermally synthesized MoS2 nanoparticles dispersed in ethanol via the drop-casting method to increase the response toward NO2 gas. The MoS2 decorated sensor shows a fast gas detection with the improved response of ( $\Delta \text{R}/\text{R}_{a}$ %) of ~69% at 150 °C for 100ppm of NO2 gas, which is 68% higher compared to the pristine sample (~42%). The sensor shows a fast response time of ~34 s and a moderate recovery time of ~95 s. The decoration of MoS2 nanoparticles has increased the surface-to-volume ratio and active sites and hence increased the number of gas molecules that can react with the surface of the sample. The sensor shows high sensitivity and selectivity toward NO2 due to increased holes and reduced barrier height in MoS2/ $\alpha $ -Fe2O3 p-p heterojunctions.