Growth mechanism of ATiO₃ (A = Ba, Sr) thin film by the hydrothermal-electrochemical method

A novel film formation technique categorized into the hydrothermal-electrochemical method has recently been developed. Growth Mechanisms of ATiO₃ (A = Ba, Sr) perovskite thin film by this technique are reviewed. The film thickness has been found to increase with an increase in the quantity of electricity passed through the Ti electrode on which the film grows. Current efficiency for the film growth is estimated to be 0.6% to 3.0%. A tracer experiment revealed that the ATiO₃ films grow at the film/electrode interface by transport of solution species, A²⁺ and OH^- (and/or H₂O), to the interface through "short-circuiting paths". A 20- or 30-nm-thick Ti oxide layer is found to exist at the interface. An elementary reaction model of ATiO₃ film formation is proposed on the basis of analyses of microstructure and composition of the thin Ti oxide layer and the potential-pH equilibrium diagram of the system Ti-H₂O.