The enhanced ferroelectricity in Sr1-δTiO3/BaTiO3 superlattices with Sr deficiency

Here we report the tunable ferroelectricity in superlattices of (Sr1-δTiO3)n/(BaTiO3)8 with δ≈5% and the maximally enhanced ferroelectricity is found in the n=6 superlattice. The room-temperature remnant polarization of n=6 is enhanced by 70% and 1120% compared to those of BaTiO3 and Sr1-δTiO3 thin films, respectively. The ferroelectric transition temperature of n=6 is 40 K higher than that of the BaTiO3 film, and is independent of the measurement frequency. The dependence of remnant field 2Pr on n coincides well with the n dependence of γ/α, which is ratio between out-of-plane and in-plane octahedral rotation angles. It thus suggests a strong correlation between the octahedral rotation pattern and the ferroelectric distortion. Our study demonstrates the importance of constructing superlattices to enhance the ferroelectric properties of the defect-engineered materials to be better than the pristine materials.