Composite metal oxide thin film based impedometric humidity sensors

[Display omitted] •Pure and composite thin films of ZnO and SnO2 are prepared by sol-gel based spin coating.•Impedometric humidity sensing studies of the proposed pure and composite sensors.•ZnO rich composite sensors show better sensor response, sensitivity and transient characteristics. Composite metal oxide based thin film based sensors are proposed to eradicate the problems faced by the single phase materials. The composite thin films of ZnO and SnO2 are expected to have significantly enhanced humidity sensing properties. In the present work, pure and composite thin films of ZnO and SnO2 are prepared by sol-gel based spin coating. The structural, optical and morphological properties of the films were studied by X-ray diffraction, Ultraviolet-Visible absorption spectroscopy and the scanning electron microscopy. The composite films with different compositions of ZnO and SnO2 phase were studied for their impedometric humidity sensing characteristics. Among the proposed sensors, the zinc rich composite sensors exhibit the maximum sensor response of 95% and sensitivity of 8.6 ± 0.5 kΩ/RH%. Further, the composite metal oxide based humidity sensors exhibit better transient characteristics and significantly lower hysteresis compared to their pure counterparts.