X-ray diffraction measurement of the effect of layer thickness on the ferroelectric transition in epitaxial KTaO3/KNbO3 multilayers

KTaO3/KNbO3 strained-layer superlattices of variable periodicity were grown by pulsed laser deposition on KTaO3 substrates. The KNbO3 layers were found to be strained in plane to match the substrate lattice parameter. Therefore, the applied strain is independent of the layer thickness. High-temperature x-ray diffraction was used to measure the ferroelectric-paraelectric phase transition temperature T-c. For superlattice periodicity Lambda less than or equal to 5.1 nm, T-c = 475 K, independent of Lambda. For Lambda > 5.1 nm, T-c increases to 825 K at Lambda = 33.8 nm.