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

Abstract

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.