Area-controlled CVD using catalytic reaction

In this work, deposition of TiO2 was performed as a typical case study to d emonstrate the concept of area-controlled CVD process, As the reactant gase s, TiCl4, H-2 and CO2 were used. In this reaction system, TiO2 is deposited by the reaction of TiCl4 with H2O which is formed by the reverse water gas shift reaction. Hence, the formation and deposition zone of TiO2 was contr olled by regulating the position of the catalyst of the reverse water gas s hift reaction and the concentration of reactant gases. At 443-473 K, TiO2 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 Tenon tube, the reaction temperature, the number of ca talyst pieces and the concentration of reactant gases. The relationship bet ween 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 C VD process is TiCl4 diffusion process. It was found to be possible to contr ol the deposition area by the proposed CVD method.