Precursors for deposition of strontium bismuth tantalate films by direct liquid injection-metallorganic chemical vapor deposition

Precursors for the deposition of Sr0.8Bi2.2Ta2O9 (SBT) thin films, Bi(tmhd)(3) (tmhd = 2,2,6,6-tetramethylheptanedionate), Bi(Ph)(3) (Ph = phenyl), Ta(OC2H5)(5), and Sr(tmhd)(2)-PMDT (PMDT = pentamethyldiethylenetriamine) were characterized by Fourier transform-infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The choice of Bi precursor significantly affects the growth process. It was found that Bi(Ph)(3) is more stable than Bi(tmhd)(3). The incorporation rate of Bi into the film is expected to be substantially lower with Bi(Ph)(3). We chose Bi(tmhd)(3) as the Bi precursor because Bi(tmhd)(3) is similar in decomposition characteristics to Ta(OC2H5)(5), and also provides a better control of Bi composition at low temperature. SBT films were deposited on a Pt/TiO2/SiO2/Si substrate by metallorganic chemical vapor deposition using a direct liquid injection at a temperature of 450 degreesC. This temperature was selected to obtain a high composition reproducibility. Films were annealed after deposition at temperatures ranging from 650 to 800 degreesC to obtain crystallized films. For the film annealed at 800 degreesC, the remanent polarization (2P(r)), and coercive field (E-c) were 16.4 muC/cm(2) and 51 kV/cm, respectively. The films showed fatigue-free characteristics up to 1.0 x 10(12) cycles under a bipolar wave of 5 V. (C) 2001 The Electrochemical Society.