Relation between Particle Growth in Solution and Composition of Mixed Titania/Vanadium Oxide Films: Implications for Chemical Bath Deposition

Abstract

Composite titania/vanadium oxide thin films were prepared by chemical bath deposition. The reaction solution consisted of aqueous solutions of ammonium vanadate and a titanium peroxo complex. Deposition could be achieved on surface-oxidized silicon substrates at reaction temperatures of 333 K. The films consisted of titania as well as vanadium(IV) and (V) oxide nanoparticles. For the elucidation of the deposition mechanism the reaction solutions were investigated by dynamic light scattering to monitor the particle agglomeration in the reaction solution and UV/Vis spectroscopy to gain information about the change in chemical composition. The deposition mechanism was discussed in terms of attachment of colloidal particles. Thereby an optimum size exists for the colloids in which deposition can take place, whereas below no deposition occurs and above only the sedimentation of larger agglomerates on the surface is possible. This kinetic control leads to rather uniform films with compositions in a narrow range.