Preparation and characterization of nanocrystalline TiO2 thin films

Nanocrystalline anatase TiO2 films have been prepared using sol–gel spin coating method. The sol has been prepared by mixing titanium isopropoxide with absolute ethanol and acetic acid at room temperature. The structural studies carried out revealed that the pristine films are amorphous in nature. The annealed films have been observed to be nanocrystalline in nature and the crystallinity has been observed to improve on annealing. The films are found to exhibit anatase phase with grain size of 19 nm and 22 nm for 450 °C and 550 °C annealed films. The high-resolution transmission electron microscope (HRTEM) image showed lattice fringes corresponding to the anatase phase of TiO2. The Raman spectra of the prepared films has been observed to be distinct without overlapping peaks suggesting that the prepared films have low level of impurity sites. The vibration peaks present in the spectra at 145 cm−1, 394 cm−1, 513 cm−1 and 635 cm−1 has been observed to unambiguously correspond to the Raman active modes of the anatase phase of TiO2.