Densification of amorphous sol-gel TiO2 films: An X-ray reflectometry study

Sol-gel TiO2 thin films were dip coated on soda lime glass substrate using tetraisopropoxide as titania precursor. Four withdrawal speeds were tested and the resulting dried thin films have been annealed at 400 degrees C, 450 degrees C and 500 degrees C for 1 h. Glancing Incidence X-ray Diffraction has revealed the amorphous nature of the thin films whatever is the annealing temperature. In order to study the thin films densification, X-ray Reflectometry curves have been fitted by a three layers Parrat model and by the Distorded Wave Born Approximation (DWBA) box model which provides more details on the Electron Density Profile. The presence of high density layers localized at the film surface and at the substrate-film interface has been evidenced for the annealed films. The DWBA fitting method allows us to point out a density gradient, probably arising from the initial packing density and to the constraint due to the substrate, along the film thickness. (C) 2009 Elsevier B.V. All rights reserved.