Fabrication of ultra-fast humidity ZITO nanoporous sensor by sol–gel technique for dynamic situation and human breath

Abstract

Measuring humidity in dynamic situation needs very high sensitive and fast response sensors. For this purpose, a new high sensitive humidity sensor based on ZnO/ITO (ZITO) composite nanostructure were designed on alumina substrate by sol–gel technique. Step by step monitoring of fabricated substrate after annealing at 400 °C was performed using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and UV–Vis techniques. An oscilloscope and digital ohmmeter were applied to determine time-varying voltage and resistance signal of the fabricated sensors, respectively, while exposed to various humidity level. Sensitivity, response, recovery time, deposited layers thicknesses, composition ratio of ZnO:ITO and annealing temperature parameters were considered to achieve optimum conditions. The optimum conditions for maximum sensitivity were obtained as 1:1(ITO:ZnO) ratio, 400 °C annealing temperature, and three times layer by layer coating. Fabricated sensor has excellent response and recovery time (1.0 and 9 s) and long life time at room temperature (25 ± 1 °C) for monitoring human breath and dynamic situation.