The film thickness dependence of the ferroelectricity of c-axis-oriented epitaxially grown Bi4Ti3O12 thin films was investigated. The c-axis-oriented Bi4Ti3O12 films with thicknesses from 35 to 400 nm were epitaxially grown on (100)CaRuO3//(100)SrTiO3 substrates by metalorganic chemical vapor deposition. The dielectric constant and the coercive field of the films were almost independent of the film thickness. These values were about 151 and 18.8 kV/cm, respectively. The spontaneous polarization Ps was almost constant at 4.0 μC/cm2 and was independent of the film thickness above 140 nm. This value is almost the same as the reported value for the single crystal along the c axis. However, the Ps value decreased with decreasing film thickness below 100 nm. Moreover, the remanent polarization continuously decreased as the film thickness decreased below 400 nm. As a result, the ferroelectric property of the epitaxially grown Bi4Ti3O12 films also depended on the film thickness and was similar to that of simple perovskite-structured ferroelectric thin films, such as Pb(Zr, Ti)O3 and (Pb, La)(Zr, Ti)O3 thin films.
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