Space Charge Effect on the Ferroelectricity in Epitaxial Ferroelectric-Paraelectric Superlattices

The authors develop a multiscale thermodynamic model to study the effect of interfacial space charge on the ferroelectricity in epitaxial ultrathin BaTiO3/SrTiO3 superlattices, incorporating the contribution of electrode-superlattice coupling. It is found that the ferroelectricity of superlattices behaves as a result of the electrostatic interactions between space charge, polarization mismatch effect, and finite screening by the real electrodes. We find that localized space charge is independent of the recovery of ferroelectricity observed by experiments. The critical thickness and total average polarization of superlattices in the presence of space charges are enhanced by the short-range electrode-superlattice coupling. (C) 2012 The Japan Society of Applied Physics