Department of Materials Science and Engineering, National University of Singapore, 117575, Singapore, Singapore.
School of Materials and Energy, Electron Microscopy Centre of Lanzhou University and Key Laboratory of Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou, 730000, PR China.
Nat Commun. 2023 Mar 30;14(1):1780. doi: 10.1038/s41467-023-37560-3.
Ferroelectric hafnia-based thin films have attracted intense attention due to their compatibility with complementary metal-oxide-semiconductor technology. However, the ferroelectric orthorhombic phase is thermodynamically metastable. Various efforts have been made to stabilize the ferroelectric orthorhombic phase of hafnia-based films such as controlling the growth kinetics and mechanical confinement. Here, we demonstrate a key interface engineering strategy to stabilize and enhance the ferroelectric orthorhombic phase of the HfZrO thin film by deliberately controlling the termination of the bottom LaSrMnO layer. We find that the HfZrO films on the MnO-terminated LaSrMnO have more ferroelectric orthorhombic phase than those on the LaSrO-terminated LaSrMnO, while with no wake-up effect. Even though the HfZrO thickness is as thin as 1.5 nm, the clear ferroelectric orthorhombic (111) orientation is observed on the MnO termination. Our transmission electron microscopy characterization and theoretical modelling reveal that reconstruction at the HfZrO/ LaSrMnO interface and hole doping of the HfZrO layer resulting from the MnO interface termination are responsible for the stabilization of the metastable ferroelectric phase of HfZrO. We anticipate that these results will inspire further studies of interface-engineered hafnia-based systems.
基于铁电氧化铪的薄膜由于与互补金属氧化物半导体技术的兼容性而引起了极大的关注。然而，铁电正交相在热力学上是亚稳的。已经做出了各种努力来稳定基于氧化铪的薄膜的铁电正交相，例如控制生长动力学和机械限制。在这里，我们通过故意控制底部 LaSrMnO 层的端基来展示一种稳定和增强 HfZrO 薄膜铁电正交相的关键界面工程策略。我们发现，在 MnO 端接的 LaSrMnO 上的 HfZrO 薄膜比在 LaSrO 端接的 LaSrMnO 上的具有更多的铁电正交相，而没有唤醒效应。即使 HfZrO 厚度薄至 1.5nm，在 MnO 端接处也可以观察到明显的铁电正交（111）取向。我们的透射电子显微镜表征和理论建模表明，HfZrO/LaSrMnO 界面的重构以及 MnO 界面端基引起的 HfZrO 层中的空穴掺杂是稳定 HfZrO 亚稳铁电相的原因。我们预计这些结果将激发对基于氧化铪的界面工程系统的进一步研究。
