Low Temperature Electrochemical Synthesis and Dielectric Characterization of Barium Titanate Films Using Nonalkali Electrolytes

Polycrystalline BaTiO₃ thin films of approximately 1 µm thickness have been synthesized on Ti substrates by an electrochemical process using nonalkali electrolytes, at temperatures as low as 55°C. The effect of various processing parameters, such as solution chemistry, atmosphere, quality of substrate surface, applied voltage, temperature, and reaction time have been discussed. Film thickness and uniformity increase with reaction time up to 24 h. The quantity of total electric charge passed through the electrolytic cell is found to govern the film thickness and uniformity. Dielectric characteristics of the as-prepared and heat-treated films have also been reported. Use of tetraethylammonium hydroxide, a nonalkali base reagent to adjust solution pH, has resulted in films having improved dielectric properties as opposed to the films prepared with alkali metal bases such as NaOH. Heat-treatment further improves the dielectric properties through a phase transition to the thermodynamically stable tetragonal phase from the as-prepared pseudo-cubic phase as confirmed by the x-ray diffraction data.