Spontaneous Polarization in an Ultrathin Improper-Ferroelectric/Dielectric Bilayer in a Capacitor Structure at Cryogenic Temperatures

Authors

Yu Yun, University of Nebraska-Lincoln
Pratyush Buragohain, University of Nebraska-Lincoln
Arashdeep Singh Thind, Washington University in St. Louis
Yuewei Yin, University of Nebraska - Lincoln
Xin Li, University of Nebraska-LincolnFollow
Xuanyuan Jiang, University of Nebraska-Lincoln
Rohan Mishra, Washington University in St. Louis
Alexei Gruverman, University of Nebraska-LincolnFollow
X. S. Xu, University of Nebraska-LincolnFollow

Date of this Version

9-26-2022

Citation

PHYSICAL REVIEW APPLIED 18, 034071 (2022). DOI: 10.1103/PhysRevApplied.18.034071

Comments

Used by permission.

Abstract

To determine the effect of depolarization and the critical thickness in improper-ferroelectric hexagonal-ferrite thin films, we investigate the polarization switching of a ferroelectric/dielectric bilayer in capacitor structures at 20 K. Experimentally, we show that the spontaneous polarization persists throughout the studied thickness range (3 to 80 unit cell), even with a thick (10-nm) dielectric layer, suggesting no practical thickness limit for applications. By fitting the effect of depolarization using the phenomenological theory, we show that the spontaneous polarization remains finite when the thickness of the ferroelectric layer approaches zero, providing a hint for the absence of critical thickness. We also find that the interfacial effects limit the multidomain formation and govern the polarization switching mechanisms.