Characterization of titania thin films prepared by reactive pulsed-laser ablation

Results are reported on the characterization of 200–250 nm thick TiOx transparent films grown at temperatures of 150 °C and 500 °C by reactive pulsed-laser ablation of a metallic Ti target under 0.13–13.3 Pa oxygen atmosphere. Film structure and composition were investigated by X-ray diffraction and X-ray photoelectron spectroscopy. The samples deposited at 150 °C reveal a mixture of amorphous TiO2 and Ti2O3, irrespective of oxygen pressure. The O:Ti atomic ratio fluctuates in their surface around 1.83 for oxygen pressure ranging between 0.13 Pa and 2.66 Pa. The samples deposited at 500 °C feature different characteristics, as a function of oxygen pressure: (a) below 2.66 Pa of O2 the films contain a mixture of significant amount of anatase and rutile TiO2 phases, along with titanium suboxides; (b) above this threshold, the rutile phase vanishes, the anatase TiO2 phase remaining dominant along with small amounts of nanocrystalline suboxides. The size of the anatase nanocrystallites decreases with the increase of oxygen pressures. The samples deposited at 500 °C feature a slight improvement of surface stoichiometry, from roughly TiO1.8 to TiO1.9. The films deposited at high substrate temperature and oxygen pressure are highly hydrophilic.