Ferroelectricity in Low-Permittivity SrZrO<sub>3</sub> Epitaxial Films
Shan Li, Yilin Wang, Mingdi Yang, Shuai Xu, Mingxuan Liu, Qiang Li, Jun Miao, Er‐Jia Guo, Kuijuan Jin, Lin Gu, Qinghua Zhang, Jinxia Deng, Xin Chen, Xianran Xing
Abstract
Bulk SrZrO 3 has an orthorhombic perovskite structure ( Pbnm ) with a central symmetry but exhibits a low dielectric constant. In this study, we reported a room-temperature ferroelectric SrZrO 3 thin film with a low dielectric constant, induced by compressive strain from the SrTiO 3 substrate. The presence of an out-of-phase boundary structure allows SrZrO 3 with a large lattice mismatch to grow epitaxially on SrTiO 3 substrates. The apparent atomic displacements in the lattice are revealed by scanning transmission electron microscopy imaging. Compressive strain induces an orthorhombic-to-monoclinic phase transition, evidenced by both the atomic structure obtained from the annular bright-field image and the structure optimized with first-principles calculation. Further first-principles calculations demonstrated that compressive strain causes a polar displacement of the Zr atom inside the ZrO 6 octahedron, which is the origin of the ferroelectricity. Our work shows a way to design novel ferroelectrics from conventional non-ferroelectric materials, which is of significant importance to robust, stable, and lead-free ferroelectrics applications.