Ferroelastic Domain Switching and Time-Resolved Negative Capacitance in Polar-Axis-Oriented Hf 0.5 Zr 0.5 O 2 Grown by Atomic Layer Epitaxy

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2025-01, Vol.21 (3), p.e2408278
• Main Authors: Jiang, Yu-Sen, Lin, Wei-En, Shiojiri, Makoto, Yin, Yu-Tung, Su, Yu-Cheng, Nien, Chih-Hung, Hsu, Chen-Feng, Hou, Vincent Duen-Huei, Chang, Chih-Sheng, Radu, Iuliana, Chen, Miin-Jang
• Format: Article
• Language: English
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202408278

Ferroelectric properties of Hf Zr O are strongly correlated with its crystallographic orientation, with the [001] direction serving as the polar axis. However, the epitaxial growth of highly polar-axis-oriented Hf Zr O layers with pronounced ferroelectricity is rarely reported. Here epitaxial (001)-oriented Hf Zr O thin films grown by atomic layer epitaxy (ALE) is demonstrated, which achieve a state-of-the-art ferroelectric polarization up to 78.9 µC cm . The epitaxial Hf Zr O layer experiences a lattice reorientation from (010) to (001) during the wake-up process, as evidenced by plane-view precession electron diffraction. Accordingly, a two-step, 90° ferroelastic domain switching model is proposed to elucidate multiple polarization switching. Furthermore, the observed polarization switching dynamics closely match with the time-resolved negative capacitance, which is quantified as an equivalent high dielectric constant of -170. This study highlights the capability of ALE to precisely control the crystallographic orientation of Hf Zr O thin films, providing deep insights into fundamental ferroelectric mechanisms.