Phase transitions and domain stabilities in biaxially strained (001) SrTiO₃ epitaxial thin films

We applied phase-field approach to investigate both ferroelectric and antiferrodistortive transitions in (001) SrTiO₃ epitaxial thin films that are strained biaxially. A domain/phase stability diagram of "misfit strain-temperature" was constructed for equibiaxially strained (001) SrTiO₃ thin films, which exhibits significant differences from previous diagrams obtained using thermodynamic analysis of a single domain. For unequibiaxially strained (001) SrTiO₃ thin films, "misfit strain-misfit strain" domain stability diagrams at several representative temperatures were obtained. The predicted phase transitions, domain stabilities, and domain structures in three different SrTiO₃ thin films under either equibiaxial or unequibiaxial strains agree well with experimental observations.