Mechanism of Enhanced NO₂ Gas Sensing Response Exhibited by CdS–SnO₂ Nanocomposite Based Thin Films

Identification of low-level concentration of nitrogen dioxide (NO 2 ) gas finds applications in fields related to air quality monitoring, environmental regulation compliance, industrial process control, health risk assessment, and climate change research to name a few. The present investigation involves studies on NO 2 sensing characteristics of sol-gel-derived CdS—SnO 2 hybrid nanocomposite sensors. Herein CdS doping concentration has been varied (0–10 wt%) and optimized in the CdS—SnO 2 sensor structure for augmented NO 2 response characteristics at 10 ppm. A comparison of bare SnO 2 and CdS—SnO 2 sensing device reveals that the addition of 3 wt% CdS in SnO 2 exhibits an elevated response of 2.9 × 10 3 with a rapid response of 17 s and quick recovery time of 30 s respectively when the sensor was operated at 90 °C. The study explains the NO 2 sensing mechanism in detail and validates the boost in sensing characteristics observed for thin film of 3 wt% CdS—SnO 2 nanocomposite sensor. Specifically, n-n junction formation at the CdS—SnO 2 interface is understood to play a crucial role in the observed enhancement in NO 2 sensing response.