Effect of the out-of-plane stress on the properties of epitaxial SrTiO₃ films with nano-pillar array on Si-substrate

A nonlinear thermodynamic formalism has been proposed to calculate the physical properties of the epitaxial SrTiO₃ films containing vertical nano-pillar array on Si-substrate. The out-of-plane stress induced by the mismatch between film and nano-pillars provides an effective way to tune the physical properties of ferroelectric SrTiO₃ films. Tensile out-of-plane stress raises the phase transition temperature and increases the out-of-plane polarization, but decreases the out-of-plane dielectric constant below Curie temperature, pyroelectric coefficient, and piezoelectric coefficient. These results showed that by properly controlling the out-of-plane stress, the out-of-plane stress induced paraelectric-ferroelectric phase transformation will appear near room temperature. Excellent dielectric, pyroelectric, piezoelectric properties of these SrTiO₃ films similar to PZT and other lead-based ferroelectrics can be expected