STRAIN TENSOR EFFECTS ON SrTiO₃ INCIPIENT FERROELECTRIC PHASE TRANSITION

ABSTRACT

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., ∼ 1% in-plnae tensional strain) from 3.905 Å 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/μ 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.

Keywords:

• SrTiO₃
• microwave dielectric properties
• tunable microwave applications
• film strain

ACKNOWLEDGMENTS

The authors gratefully acknowledge Jeffrey H. Haeni and Darrell G. Schlom at Pennsylvania State University for providing the SrTiO₃ film samples.