Strain tensor effects on SrTiO3 incipient ferroelectric phase transition

Structural distortion of ferroelectric thin films caused by film strain has a strong impact on the microwave dielectric properties. SrTiO3 thin films epitaxially grown on (110) DyScO3 substrates using molecular beam epitaxy (MBE) are extremely strained (i.e., similar to 1% in-plane tensional strain) from 3.905 angstrom of bulk SrTiO3. The room temperature dielectric constant and its tuning of the films are observed to be 6000 and 75% with an electric field of 1 V/mu m, respectively. The control of strain in SrTiO3 provides a basis for room temperature tunable microwave applications by elevating its phase transition peak to room temperature. Also, a significant in-plane anisotropy in dielectric constant and tuning was observed in these SrTiO3 films. The observed in-plane anisotropic dielectric properties have been interpreted based on the phenomenological thermodynamics of film strain.