ENHANCED ETHANOL VAPOR SENSING OF SnO₂/ZnO NANOCOMPOSITE FILMS DEPOSITED BY SPRAY PYROLYSIS

Abstract

This study focuses on SnO₂/ZnO composite films deposited on glass substrates at 400°C using a spray pyrolysis method. The crystal structures analyzed using X-ray diffraction confirm the presence of SnO₂ and ZnO phases. The number and intensity of SnO₂ diffraction peaks increase with the increase in Sn/Zn ratios. The optical properties of ZnO, SnO₂, and SnO₂/ZnO composite films, reveal that the absorption edge of the composite films shift toward the absorption edge of SnO₂ as the Sn/Zn ratio increases. The band gaps of SnO₂ and ZnO were found to be 3.94 eV and 3.25 eV, respectively. The I-V curve of the composite films are nonlinear due to the formation of a heterojunction. Scanning electron microscopy images reveal morphological changes from hexagonal dipyramid crystals to spherical particles as the Sn/Zn ratio increased. Particle sizes reduces to around 10 nm at Sn/Zn ratios of 1/2. The sensitivity of films improves significantly with increased Sn/Zn ratios up to 1/2. The increased sensitivity is attributed to the enhanced surface morphology and smaller grain sizes. Optimal sensing performance is achieved at 250°C, where the response increased with temperature before reaching a saturation point. Higher Sn/Zn ratios improved sensor response. The films deposited with Sn/Zn ratio of 1/2 exhibit the highest sensor response.