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Ferroelectric Transition in Compressively Strained SrTiO3 Thin Films

We report the temperature dependent capacitance-voltage characteristics of Pt/SrTiO3 Schottky diodes fabricated using compressively strained SrTiO3 thin films grown on (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) substrates. The measurements reveal a divergence of the out of plane dielectric constant of SrTiO3 peaked at ~140K, implying a ferroelectric transition. A Curie-Weiss law fit to the zero-bias dielectric constant suggests a Curie temperature of ~56 K. This observation provides experimental confirmation of the theoretical prediction of out of plane ferroelectricity in compressively strained SrTiO3 thin films grown on LSAT substrate. We also discuss the roles of the field-dependent dielectric constant and the interfacial layer in SrTiO3 on the extraction of the Curie temperature.