Preparation of a TiO₂ Film Coated Si Device for Photo-Decomposition of Water by CVD Method Using Ti(OPri)₄

Growth of a TiO2 film on a Si wafer by CVD method was studied for a new design of chemically stable device which is useful in the visible region and increases the efficiency of the photocatalytic decomposition process of water. This design is made up of a monolithic structure of a TiO2 thin film and a Si solar cell. The TiO2 film was deposited on a Si substrate by the vapor phase reaction of Ti(OPri)4 with water at temperatures from room temperature to 473 K. At room temperature, a rough TiO2 film with a nano-sized cone shape deposit was observed by AFM. The smooth TiO2 film of ∼10 nm thickness was obtained by the reaction of 80 Pa Ti(OPri)4 and 493 Pa water vapors at 473 K for 10.8 ks. The surface and the thickness of the film became rougher and thicker, respectively, with increasing pressure of Ti(OPri)4.