Titanium dioxide thin films were deposited on crystalline silicon (100) and fused quartz substrates by spray pyrolysis (SP) of an aerosol, generated ultrasonically, of titanium diisopropoxide. The evolution of the crystallization, studied by X-ray diffraction (XRD), atomic force (AFM) and scanning electron microscopy (SEM), reflection and transmission spectroscopies, shows that the deposition process is nearly close to the classical chemical vapor deposition (CVD) technique, producing films with smooth surface and good crystalline properties. At deposition temperatures below 400 degreesC, the films grow in amorphous phase with a flat surface (roughnesssimilar to0.5 nm); while for equal or higher values to this temperature, the films develop a crystalline phase corresponding to the TiO2 anatase phase and the surface roughness is increased. After annealing at 750 degreesC, the samples deposited on Si show a transition to the rutile phase oriented in (111) direction, while for those films deposited on fused quartz no phase transition is observed. (C) 2004 Elsevier B.V. All rights reserved.