Effects of Annealing Treatment on Optical Properties of Anatase TiO₂ Thin Films

Titanium dioxide thin films were prepared onto well cleaned glass substrates by sol-gel dip-coating method. X-ray diffraction studies showed amorphous structure for the as-deposited films and poly crystalline anatase for the annealed films. The optical constants of the films were calculated from the UV-VIS transmission spectra. The allowed direct optical bandgap of the films was estimated to be in the range from 3.38 to 3.13 eV and its refractive index was found to increase, while the porosity decreases at higher annealing temperatures making the film compact and dense