Abstract: The nanocomposite silica-titania thin films were deposited with a dip-coating method on silicon wafers,
fused quartz and K9 glass substrates from a sol made by a two-step hydrolysis method. A high-pressure mercury lamp was used to act as irradiation treatment.
AFM, ellipsometry, FTIR, UV-Vis spectrophotometer and XRD were used to characterize the structure and optical properties of the as-grown and UV
irradiated films. The results show that the UV-irradiation is one of the effective methods to densify the sol-gel thin films at a relative low
temperature. The densification mechanism is different from that of the conventional thermal treatment. Electron excitation is induced directly
by the UV light irradiation ,which is able to cause the bond cleavage in gel network and make gel films densify through the rearrangement of
the gel structure eventually.

Key words: nanocomposie silica-titania thin films, sol-gel process, UV light irradiation