Stress effect on the ferroelectric-to-paraelectric phase transition in heteroepitaxial (Ba,Sr)TiO3/(001)MgO thin film studied by Raman scattering and x-ray diffraction -: art. no. 052103

We report experimental evidence for the stress-induced tetragonal symmetry of the paraelectric phase in heteroepitaxial (Ba0.7Sr0.3)TiO3 thin film deposited on the (001)MgO substrate. Our Raman and x-ray-diffraction data evidently show that symmetry of the paraelectric phase is tetragonal well above the Curie temperature due to the two-dimensional compressive stresses imposed on the film by the substrate. On approaching the deposition temperature the thermoelastic compressive stresses vanish and Raman measurements revealed cubic symmetry of the paraelectric phase.