Evaluation of precursors for DLI MOCVD of ferroelectric BLT

Abstract

Precursors for the direct liquid injection (DLI) metallorganic chemical vapor deposition (MOCVD) of Bi4-xLaxTi3O12 (BLT) thin films, Bi(phenyl)(3) [Bi(Ph)(3)], Bi(2,2,6,6-tetramethylheptanedionate)(3)[Bi(tmhd)(3)], La(tmhd)(2)-pentamethyldiethylenetriamine) [La(tmhd)(2)-PMDT], and Ti(dimethylaminoethoxide)(4) [Ti(dmae)(4)] were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry, and thermogravimetric analysis. The reactions among Bi, La, and Ti precursors in a single-mixture solution was identified using a H-1-nuclear magnetic resonance spectrometer and it was shown that Bi( Ph) 3 was better than Bi(tmhd)3 as a Bi precursor because Bi(tmhd)(3) reacted with Ti(dmae)(4) in the solvent. The gas phase decomposition temperatures of three precursors, Bi(Ph)(3), La(tmhd)(3)-PMDT, and Ti(dmae)(4) were found with FTIR to be 400, 375, and 325degreesC, respectively. Evaporator temperature was optimized from the deposition rate of the single oxide from each precursor. The deposition behavior could be explained in terms of the precursor characteristics. Fatigue-free and highly c axis oriented BLT thin films were grown on Pt/TiO2/SiO2/Si at the deposition temperature of 400degreesC. For the BLT film annealed at 650degreesC, the remanent polarization (2P(r)) and coercive field (E-c) were 12 muC/cm(2) and 56 kV/cm, respectively. The BLT capacitors did not show any significant fatigue up to 4 x 10(10) cycles at a frequency of 1 MHz. (C) 2003 The Electrochemical Society.