Sol-gel derived SrBi₂Ta₂O₉ thin films and electrical properties

Ferroelectric SrBi₂Ta₂O₉ thin films were prepared from Sr metals, Ta-ethoxide and Bi, 2-ethylhexanoate. The films were prepared from both stoichiometric and 10 mol% Bi rich solutions. The stoichiometric film crystallized at 800°C had a spontaneous polarization value of 5 μC/cm2. The Bi rich film had lower crystallinity, finer grains and a smaller polarization. It was found to be necessary to anneal the films at high temperatures or for long time to achieve ferroelectricity. The non-crystalline states of sol-gel derived films differ from that observed in films deposited by physical vapor deposition. Crack free films were produced with the film thicknesses of 0.4 μm.