Preparation of $TiO2$ thin films by laser ablation for photocatalytic applications

Thin titanium dioxide $(TiO2)$ films were deposited by pulsed KrF excimer laser ablation deposition system using a titanium oxide target. The effects of substrate temperature and oxygen partial pressure on the phase formations of various microstructures were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), Raman scattering spectroscopy, and UV-Vis spectrophotometer. The film structures range from amorphous to mixed phase of anatase and rutile to pure anatase. Increasing the substrate temperature improves the quality of anatase phase of crystalline $TiO2$ films. The oxygen pressure in the range between 15 and 60 mTorr shows a single anatase phase in $TiO2$ films while the rutile and anatase mixed phases were observed elsewhere. The band gap of $TiO2$ films varied from 2.72 to 3.27 eV with increasing oxygen partial pressure while the film structures changed from rutile phase to anatase phase. The surface area of $TiO2$ films increased as oxygen partial pressure in film deposition. The photocatalytic performance evaluated by degradation of methylene blue in UV light was distinguishable in the $TiO2$ films with high anatase phase and surface area.