Ferroelectricity in Epitaxial Perovskite Oxide Bi<sub>2</sub>WO<sub>6</sub> Films with One-Unit-Cell Thickness
Song Zhou, Lei Liao, Lan Chen, Baojie Feng, Xiaoyue He, Xuedong Bai, Chuangye Song, Kehui Wu
Abstract
Retaining ferroelectricity in ultrathin films or nanostructures is crucial for miniaturizing ferroelectric devices, but it is a challenging task due to intrinsic depolarization and size effects. In this study, we have shown that it is possible to stably maintain in-plane polarization in an extremely thin, one-unit-cell thick epitaxial Bi 2 WO 6 film. The use of a perfectly lattice-matched NdGaO 3 (110) substrate for the Bi 2 WO 6 film minimizes strain and enhances stability. We attribute the residual polarization in this ultrathin film to the crystal stability of the Bi–O octahedral framework against structural distortions. Our findings suggest that ferroelectricity can surpass the critical thickness limit through proper strain engineering, and the Bi 2 WO 6 /NdGaO 3 (110) system presents a potential platform for designing low-energy consumption, nonvolatile ferroelectric memories.