TiO2 thin films by ultrasonic spray pyrolysis

Titanium dioxide (TiO2) thin film have attracted wide interest as photovoltaic, dielectric and photocatalytic material. In this study, the ultrasonic spray pyrolysis method was used to fabricate TiO2 thin films because of its low-cost operation, absence of vacuum system and convenience of use. The films were sprayed from solution containing titanium(IV) isopropoxide, acetylacetone and ethanol onto microscopy glass and n-type Si(100) substrates at temperatures of 200 to 500 degrees C. The resulting films were annealed at 500 degrees C and 700 degrees C for 1 hour in air. In the present study, optical, structural and electrical properties of produced TiO2 thin films were investigated as a function of deposition temperature. TiO2 films deposited <= 400 degrees C show optical transmittance of ca. 80% in the visible region. The band gap of TiO2 films decreased from 3.52 to 3.25 eV as the deposition temperature increased from 200 to 500 degrees C. Asdeposited films prepared below 500 degrees C were amorphous, whereas crystalline anatase films were obtained at 500 degrees C. Further annealing at 700 degrees C in air led to anatase crystalline formation when films were deposited below 500 degrees C whereas the films deposited at 500 degrees C consist of anatase and rutile phases.