Area-Controlled CVD Using Catalytic Reaction.

Abstract

In this work, deposition of TiO 2 was performed as a typical case study to demonstrate the concept of area-controlled CVD process. As the reactant gases, TiCl 4 , H 2 and CO 2 were used. In this reaction system, TiO 2 is deposited by the reaction of TiCl 4 with H 2 O which is formed by the reverse water gas shift reaction. Hence, the formation and deposition zone of TiO 2 was controlled by regulating the position of the catalyst of the reverse water gas shift reaction and the concentration of reactant gases. At 443-473 K, TiO 2 was deposited on a inner surface of tetrafluoroethylene tube, where a certain amount of catalyst pieces were set at the close end. The deposition profile was measured with SEM. The deposition area depended on the length of the Teflon tube, the reaction temperature, the number of catalyst pieces and the concentration of reactant gases. The relationship between the deposition area and the above parameters could be interpreted by a model, which is based on an assumption that the rate-limiting step in the CVD process is TiCl 4 diffusion process. It was found to be possible to control the deposition area by the proposed CVD method.