Effect of thermal annealing on the structure and microstructure of TiO2 thin films

Abstract

Nanostructured TiO2 thin films have been prepared through chemical route using sol-gel and spin coating techniques. The deposited films were annealed in the temperature range 400-1000 degrees C for 1 h. The structure and microstructure of the annealed films were characterized by GAXRD, micro-Raman spectroscopy and AFM. The as-deposited TiO2 thin films are found to be amorphous. Micro-Raman and GAXRD results confirm the presence of the anatase phase and absence of the rutile phase for films annealed up to 700 degrees C. The diffraction pattern of the film annealed at 800 to 1000 degrees C contains peaks of both anatase and rutile reflections. The intensity of all peaks in micro-Raman and GAXRD patterns increased and their width (FWHM) decreased with increasing annealing temperature, demonstrating the improvement in the crystallinity of the annealed films. Phase.. transformation at higher annealing temperature involves a competition among three events such as : grain growth of anatase phase, conversion of anatase to rutile and grain growth of rutile phase. AFM image of the as-deposited films and annealed films indicated exponential grain growth at higher temperature.