Effect of film thickness on structural and optical properties of TiO2 thin films

Titanium Dioxide (TiO₂) thin films have been prepared from solution of TTIP (Titanium Tetra Isopropoxide), acetic acid and ethanol on glass substrates by sol - gel dip coating technique. The films coated for different coating cycles were annealed at a temperature of 450°C for one hour. The annealed films were characterized by X - Ray diffraction (XRD) method, UV - Visible and Photoluminescence (PL) spectroscopy, Field Effect Scanning Electron Microscopy (FESEM) and Energy Dispersive X - Ray Analysis (EDAX). From XRD analysis, the crystallite size was found to increase from 19.4 nm to 71.3 nm and the phase changes from anatase to rutile with increase in the number of coating cycles. The TiO₂ thin films have high transparency in the visible range.The transmittance and the optical band gap found to reduce with increase in number of coating cycles. The PL spectra of TiO₂films have two peaks at 485 nm and 530 nm and intensity increases with increase in coating cycles. Surface morphology from FESEM images reveal that the films are becoming denser and roughness increases with increase in the number of coating cycles. These results suggest that the nanocrystalline TiO₂ thin films are attractive material for photo catalytic applications.