F. Gracia, F. Yubero, J.P. Holgado, J.P. Espinós, A.R. González-Elipe, T. Girardeau
Thin Solid Films, 500 (2006) 19-26
doi: 10.1016/j.tsf.2005.10.061

SiO₂/TiO₂ optical thin films with variable compositions have been prepared by ion beam induced and plasma enhanced chemical vapour deposition (IBICVD and PECVD). While the films obtained by IBICVD were very compact, the PECVD ones with a high content of Ti presented a columnar microstructure. The formation of Si–O–Ti bonds and a change in the environment around titanium from four- to six-coordinated has been proved by vibrational and X-ray absorption spectroscopies. The refractive index increased with the titanium content from 1.45 to 2.46 or 2.09 for, respectively, the IBICVD and PECVD films. Meanwhile, the band gap decreased, first sharply and then more smoothly up to the value of pure TiO₂. It is concluded that the optical properties of SiO₂/TiO₂ thin films can be properly tailored by using these two procedures.