PREPARATION AND ELECTRIC PROPERTIES OF FERROELECTRIC BI4TI3O12 THIN-FILMS BY MOCVD

Bismuth titanate film was prepared by the simultaneous deposition of Bi2O3 and TiO2 on heated substrates at 750-degrees-C under a reduced pressure of 6 Torr. Triphenyl bismuth and tetraisopropoxy titanium were used as source materials. Prior to the preparation of bismuth titanate, the deposition behavior of Bi2O3 and TiO2 films was examined independently. Stoichiometric film of Bi4Ti3O12 was obtained on MgO (100) and Si (100) substrates with the deposition rates of 200 approximately 300 angstrom/min. The film was colorless or light yellow and transparent, and the crystal structure was aggregative with a single phase of orthorhombic form and oriented along (0212) face on the MgO (100) substrate. The dielectric constant and tan-delta were around 100 to 120 and 0.015 to 0.025 respectively. Typical D-E hysteresis loops were observed on as-grown films at 750-degrees-C. Remanent polarization and coercive field were 0.6 to 1.0-mu-C/cm2 and 25 to 30 kV/cm respectively. These values were approached those of bulk ceramics by a post anneal treatment.