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
Department of Materials Science and Engineering, National Taiwan University, Taipei, 106319, Taiwan.
Graduate School of Advanced Technology, National Taiwan University, Taipei, 106319, Taiwan.
Small. 2025 Jan;21(3):e2408278. doi: 10.1002/smll.202408278. Epub 2024 Dec 15.
Ferroelectric properties of HfZrO 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 HfZrO layers with pronounced ferroelectricity is rarely reported. Here epitaxial (001)-oriented HfZrO 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 HfZrO 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 HfZrO thin films, providing deep insights into fundamental ferroelectric mechanisms.
HfZrO的铁电性能与其晶体取向密切相关，其中[001]方向为极轴。然而，很少有关于具有明显铁电性的高极轴取向HfZrO层外延生长的报道。本文展示了通过原子层外延（ALE）生长的外延（001）取向的HfZrO薄膜，其实现了高达78.9 µC/cm的先进铁电极化。通过平面进动电子衍射证明，外延HfZrO层在唤醒过程中经历了从（010）到（001）的晶格重新取向。因此，提出了一个两步、90°铁弹性畴切换模型来解释多重极化切换。此外，观察到的极化切换动力学与时间分辨负电容密切匹配，其量化为-170的等效高介电常数。这项研究突出了ALE精确控制HfZrO薄膜晶体取向的能力，为深入了解基本铁电机制提供了深刻见解。
