Impact of NiO nanoparticle decoration on the surface of SnO₂ thin films for gas sensing

Thin film of tin oxide (SnO₂) deposited by spray pyrolysis with the aim of using the samples for gas sensing. To further enhance its gas-sensing properties, NiO nanoparticles (NPs) were decorated on the SnO₂ surface at various concentrations. The bare and decorated samples were subjected to thorough investigation on their properties by X-ray diffraction, field emission scanning electron microscopy, and optical absorbance spectroscopy. In particular, the NiO NP density was carefully controlled by adjusting the deposition process. The deposition of NiO NPs significantly enhanced the NO₂ sensitivity of the SnO₂ thin film compared to their unmodified counterparts. Our investigations also delved into understanding mechanism of sensing. The deposition of NiO NPs onto the SnO₂ surface facilitated the formation of p–n heterojunctions. These heterojunctions play a crucial role in modulating the conducting channels between neighboring particles, thereby extensively enhancing the overall sensing effectiveness of the device. This study presents a new strategy for the effective utilization of NiO NPs as a strategy for enhancing the sensing efficiency of SnO₂ thin films and underscores the importance of heterojunction formation in enhancing the sensor performance.