Ba Titanate and Barium/Strontium Titanate Thin Films from Hydroxide Precursors: Preparation and Ferroelectric Behavior

Randomly oriented ferroelectric BaTiO₃ and (Ba_0.6Sr_0.4) TiO₃ thin films on platinum coated Si (100) were prepared by a sol-gel method. The precursor solutions were derived from barium hydroxide or a mixture of barium/strontium hydroxides dissolved in acetic acid and titanium butoxide. Polarization versus applied voltage hysteresis studies indicated a remanent polarization of 3 µC/cm² and a coercive field of 43.4 kV/cm for BaTiO₃ films annealed at 800°C for 1 h. Corresponding parameters for (Ba_0.6Sr_0.4)TiO₃ films annealed at 800°C were found to be 7.2 µC/cm² and 102.7 kV/cm, respectively. Microstructural study of the surface morphology of these films indicated grains of less than 0.1 µm in size. The leakage current for (Ba_0.6Sr_0.4)TiO₃ films was found to be two orders of magnitude lower than that for BaTiO₃ films.