Preparation and characterization of Al-Ti mixed oxide thin films

Abstract

This paper reports the preparation and characterization of thin films of Al-Ti mixed oxides. Films of different compositions ranging from a cationic content of Ti of 92.6% to 18.8% (i.e. Al/Ti ratios from 0.08 to 4.3) have been prepared by ion beam induced CVD (IBICVD). The films have been characterized by different methods including UV-VIS spectroscopy, XRD and X-ray absorption spectroscopy (XAS). It is found that the optical properties of the films (refraction index and band gap energy) deduced from the UV-VIS absorption spectra vary linearly with the titanium content from 1.45 (0% Ti) to 2.55 (100% Ti). The films were amorphous after preparation, but for Al/Ti ratios lower than 1.5, a partial crystallization into the anatase structure of titanium dioxide was observed after annealing at 823 K. This contrasts with the formation of the rutile structure observed when annealing thin films of TiO 2 or TiO 2-Al 2O 3 bilayers prepared by the same procedure. In both cases, annealing did not produce any significant change in the values of the optical parameters.