Ferroelectric thin film bismuth titanate prepared from acetate precursor

Bismuth Titanate (Bi₄Ti₃O₁₂) thin films were fabricated by spin coat deposition - rapid thermal processing (RTP) technique. Acetate derived solution for deposition was synthesized by blending dissolved bismuth acetate in aqueous acetic acid, and then adding with titanium acetate. A series of electrically insulating, semiconducting and conducting substrates were evaluated for Bi₄Ti₃O₁₂ films deposition. While X-ray diffraction and TEM analyses indicated that the initial perovskite crystallization temperature was 500°C or less for these Bi₄Ti₃O₁₂ films, a 700°C crystallization treatment was used to obtain single phase perovskite films. Bi₄Ti₃O₁₂ film crystallographic orientation was shown to depend on three factors: substrate, the number of coating layers and thermal processing. While preferred c-direction orientation was observed for films deposited on silver foil substrates, preferred a-direction orientation was obtained for films deposited on both Si and Pt coated Si wafers. The films were dense, smooth, crack-free and had grain sizes ranging from 20 nm to 400 nm. Film thickness and refractive index were determined using a combination of ellipsometry, waveguide refractometry and TEM measurements. Both low field dielectric and ferroelectric properties were measured for an 800 nm thick film deposited on a Pt coated MgO substrate. A remanent polarization of 38 μC/cm² and a coercive field of 98 kv/cm was measured for this film that was crystallized at 700°C.