Ferroelectric Properties and Fatigue Characteristics of Bi4Ti3O12 Thin Films by Sol-Gel Processing

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Abstract
Stoichiometric Bi4Ti3O12 thin films were prepared by sol-gel processing. This paper discusses the synthesis of polymerizable solutions containing Bi and Ti, ferroelectric properties and fatigue characteristics of the resulting Bi4Ti3O12 thin films. The complex alkoxide was prepared by allowing Bi acetate to react with Ti alkoxides. Bismuth acetate and titanium methoxyethoxide, the solvents 2-methoxyethanol and glacial acetic acid were selected based on their successful use in a number of related systems. Thin films of Bi4Ti3O12 were obtained onto platinized Si substrates by spin casting, followed by heat treated at 700° C. The value of the dielectric constant and loss at 400 Hz, 100 mVrms, 25° C of this virgin films were 132 and 0.8%, respectively. This thin films with single phase layerd perovskite-like structure had very good D-E hysteresis characteristics. The remnant polarization, P r, and coercive field, E c, of this virgin films were 5.5 µ C/cm2 and 6.2 kV/cm, respectively. The remnant polarization of this thin films, P r +, P r -, and 2P r, were nearly constant up to 108 cycles. At 4×108 cycles, the decay in remnant polarization, P r +, P r -, and 2P r, was observed to be about 35% of the initial values, respectively. The coercive field was drastically increased after 108 cycles. The D-E hysteresis loop after 108 cycles was not completely saturated. After 108 cycles, leakage current was typically increased. We considered that the fatigue characteristics observed in our study are resulted from increasing of leakage current.