Photo-induced preparation of (Ta2O5)1ÿx(TiO2)x dielectric thin ®lms using sol±gel processing with xenon excimer lamps

We report the growth of thin ®lms of Ta2O5 doped with TiO2 on Si (1 0 0) substrates at low temperatures by a new photoinduced sol±gel process. Polymeric sols were formed through hydrolysis and condensation of tantalum ethoxide mixed with titanium isopropoxide. These were then spin-coated on the substrates and irradiated by Xe2 excimer lamps operating at a wavelength of 172 nm. The chemical bonding changes in the thin ®lms were analysed by Fourier transform infrared spectroscopy (FTIR), which con®rmed densi®cation of the ®lms and the removal of H2O and OH groups after some 10 min irradiation at 3008C. Layer thicknesses between 18±140 nm were readily achievable by this technique whose refractive index, n, increased from 1.6 after spin on to 2 after irradiation. Film thickness and refractive index were found to be dependent on exposure time, substrate temperature and ®lm composition. Maximum values of n were recorded at a TiO2 content of 8%. # 2000 Elsevier Science B.V. All rights reserved