Highly Porous Nanocluster TiO2 Films Deposited using APCVD in an Excess of Water Vapour

This paper describes high porosity titanium dioxide (TiO2) films deposited via atmospheric pressure chemical vapour deposition (APCVD) using tetraisopropyl titanate at deposition temperatures (Tdep) of 250C and 450C in excess water vapour. Films deposited at low Tdep exhibit a very low refractive index (nfilm) and high porosity (), up to 87% of the bulk rutile phase. High-temperature sintering, performed at either 450C or 1000C, can be used to tailor the films properties by crystallising the nanoclusters into the anatase or rutile phase, while retaining a low nfilm and high . The nanoporous nature of the films has significantly retarded the transformation from anatase to rutile, and after sintering for 6 hr at 1000C, the anatase fraction is still greater than 79%. Such TiO2 thin films with a high surface area to volume ratio are suitable for use in dye-sensitized solar cells and gas sensors. * Correspondence to: Dr. Bryce Richards, tel: +61 2 9385 7858, fax: +61 2 9662 4240, email: [email protected]