Effect of ethanol concentration on the porosity of spray pyrolyzed TiO2 films and their utility as humidity sensor

Titanium oxide films were prepared on ITO coated glass substrates at 350 °C using titanium (IV) isopropoxide, acetylacetonate and absolute ethanol as precursors by spray pyrolysis technique. The prepared films were characterized by X-ray diffraction, Scanning electron microscope, Fourier transform infrared spectroscopy and Energy dispersive analysis of X-rays. Estimated optical and electrical parameters such as refractive index, porosity, dielectric constant, energy band gap, carrier concentration, mobility by UV-Vis spectrophotometer, Hall effect and Van der pauw techniques were found to vary with ethanol volumetric concentration of 22.5-23. The observed increase in porosity from 45-59% facilitates the adsorption of water molecules inside films. The capacitance and resistance of metal-insulator-semiconductor structure were found to vary between 1.08-3.48 nF and 436-15 kΩ with increase in relative humidity. The fabricated humidity sensor found to posses 4s criterion such as sensitivity, stability and response-recovery times as 180%, ± 10% and 58-106 s, respectively.