F. Gracia, F. Yubero, J.P. Espinós, J.P. Holgado, A.R. González-Elipe, T. Girardeau
Surface and Interface Analysis, 38 (2006) 752-756 (2006)
SixTi1−xO2 optical thin films with variable compositions varying from pure TiO2to pure SiO2 have been prepared by ion beam induced chemical vapor deposition (IBICVD). It has been found that the refractive index of the films increases with the content of titanium, from about 1.46 to 2.35. Band gap energies have been determined by optical methods and reflection electron energy loss spectroscopy (REELS), both techniques showing a similar evolution consisting of a sharp decay from the value of pure SiO2 to the samples with 2% Ti and then a smoother decrease up to the value of pure TiO2 (i.e. 3.2 eV). Changes also occur in the value of the binding and kinetic energies (KEs) of the Ti and Si photoemission and auger peaks, respectively, as measured by X-ray photoelectron spectroscopy (XPS). The refractive indices of the films have been compared with the value of the auger parameters of Ti and Si. A good correlation exists between these two parameters as a function of the titanium content. This confirms that both depend on the polarizability of the medium and shows that XPS can be used for the assessment of optical properties of complex oxide materials.