Titanium dioxide films prepared by photo-induced sol–gel processing using 172 nm excimer lamps

We report the growth of single- and multilayer films of titanium dioxide (TiO2) on Si(100) substrates at low temperature by a new photo-induced sol–gel process. Polymeric TiO2 sols prepared by the hydrolysis and condensation of titanium isopropoxide were spin-coated on the silicon substrate and then irradiated by an Xe∗2 excimer vacuum ultraviolet (VUV) lamp operating at a wavelength of 172 nm. Films with thicknesses between 10 and 200 nm were achieved readily by this technique. The effects of spin speed, irradiation time and substrate temperature on the films formed have been studied. The chemical bonding changes in the thin films were analysed by Fourier transform infrared spectroscopy (FTIR), while thickness and refractive indices were determined by ellipsometry. FTIR confirmed the removal of H2O and OH groups after VUV irradiation for 10 min at 300°C. The refractive index reached a value of 2.4, which compares favourably with the value of 2.58 recorded for the bulk material, while optical transmittance values in the visible region of the spectrum between 85 and 95% were obtained on quartz substrates.