Al-doped TiO2-SiO2 gel-glass thin films on silicon wafers were prepared using a sol-gel method combined with a multi-layer spin coating technique. The precursor to the glass films was obtained by introducing aluminium nitrate with ethanol solution into the hydrolysis system of tetraethylorthosilicate as a dopant. X-ray photoelectron spectroscopy (XPS) depth profiling analysis of the glass films showed an excellent homogeneity of elemental composition. Titanium ions were indicated to exist in Si-O-Ti hetero-condensation forms. The microstructure of the film was investigated using an atomic force microscope across the crater created by Ar+ beam sputtering. The thickness and the refractive index of the film were estimated by means of the reflect spectra measurement. (c) 2006 Elsevier B.V. All rights reserved.