Influence of the temperature on the properties of sputtered titanium oxide films

Titanium oxide thin films were elaborated by the radio frequency (rf) magnetron sputtering method. The influence of the substrate temperature during the deposition and the annealing temperature on the film properties has been studied. The films deposited without heating were amorphous. The crystallinity starts by heating the substrate at a temperature of 350 °C. Various phases of titania were identified by X-ray diffraction (XRD) and Fourier transformed infrared (FT-IR) measurements. The microstructure of the films was observed by scanning electron microscopy. It varies from a columnar structure to a mixed compact and columnar one. The composition of the coatings was determined by Rutherford backscattering spectrometry. Hyperstoichiometric films were obtained on unheated substrates. The O/Ti atomic ratio decreases when the substrate and annealing temperatures increase. Thermogravimetric studies and infrared investigations allow to precise the form of the oxygen excess measured in the as deposited films. The optical constants (refractive index, extinction coefficient, optical band gap) were determined by ultraviolet-visible spectrometry according to the envelope technique. They were found to vary in a wide range; these variations were correlated mainly to structural evolutions.