PREPARATION OF BARIUM-TITANATE FILMS AT 55-DEGREES-C BY AN ELECTROCHEMICAL METHOD

Work by previous investigators has shown that BaTiO3 films can be synt hesized from solution over temperature ranges from 80-degrees-C to gre ater than 200-degrees-C. In the present work, electrically insulating crystalline films of BaTiO3 have been electrochemically deposited on t itanium substrates at temperatures as low as 55-degrees-C. Auger spect roscopic analyses with depth profiling indicate that a titanium oxide layer whose thickness is governed by current density acts as a precurs or to BaTiO3. Formation of BaTiO3 is found to be favored only in highl y alkaline solutions. This is consistent with the phase stability repo rted for the Ba-Ti-CO2-H2O system at 25-degrees-C. Lower processing te mperatures (55-degrees-C) favor the formation of thick, electrically r esistive, and well-crystallized BaTiO3 films, apparently due to increa sed oxygen solubility in the electrolyte solution. Films produced at 1 00-degrees-C are much thinner and are electrically conductive due to f issures and pores in their microstructure. Initial studies on the effe ct of current density indicate the formation of thinner and porous fil ms with thicker titanium oxide intermediate layers.