Interface-engineered ferroelectricity of epitaxial Hf0.5Zr0.5O2 thin films

Shu Shi; Haolong Xi; Tengfei Cao; Weinan Lin; Zhongran Liu; Jiangzhen Niu; Da Lan; Chenghang Zhou; Jing Cao; Hanxin Su; Tieyang Zhao; Ping Yang; Yao Zhu; Xiaobing Yan; Evgeny Y Tsymbal; He Tian; Jingsheng Chen

doi:10.1038/s41467-023-37560-3

Interface-engineered ferroelectricity of epitaxial Hf_0.5Zr_0.5O₂ thin films

Nat Commun. 2023 Mar 30;14(1):1780. doi: 10.1038/s41467-023-37560-3.

Authors

Shu Shi^#¹, Haolong Xi^#^{2

3}, Tengfei Cao^#⁴, Weinan Lin^#⁵, Zhongran Liu³, Jiangzhen Niu⁶, Da Lan¹, Chenghang Zhou¹, Jing Cao⁷, Hanxin Su¹, Tieyang Zhao¹, Ping Yang⁸, Yao Zhu⁹, Xiaobing Yan¹⁰, Evgeny Y Tsymbal¹¹, He Tian^{12

13}, Jingsheng Chen¹⁴

Affiliations

¹ Department of Materials Science and Engineering, National University of Singapore, 117575, Singapore, Singapore.
² 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.
³ Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China.
⁴ Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588-0299, USA.
⁵ Department of physics, Xiamen University, Xiamen, 361005, China.
⁶ Key Laboratory of Brain-Like Neuromorphic Devices and Systems of Hebei Province, Hebei University, Baoding, 071002, PR China.
⁷ Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 138634, Singapore, Singapore.
⁸ Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, 117603, Singapore, Singapore.
⁹ Institute of Microelectronics, Agency for Science, Technology and Research (A*STAR), 138634, Singapore, Singapore.
¹⁰ Key Laboratory of Brain-Like Neuromorphic Devices and Systems of Hebei Province, Hebei University, Baoding, 071002, PR China. yanxiaobing@ime.ac.cn.
¹¹ Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588-0299, USA. tsymbal@unl.edu.
¹² Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China. hetian@zju.edu.cn.
¹³ School of Physics and Microelectronics, Zhengzhou University, Zhengzhou, 450052, China. hetian@zju.edu.cn.
¹⁴ Department of Materials Science and Engineering, National University of Singapore, 117575, Singapore, Singapore. msecj@nus.edu.sg.

^# Contributed equally.

Abstract

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 Hf_0.5Zr_0.5O₂ thin film by deliberately controlling the termination of the bottom La_0.67Sr_0.33MnO₃ layer. We find that the Hf_0.5Zr_0.5O₂ films on the MnO₂-terminated La_0.67Sr_0.33MnO₃ have more ferroelectric orthorhombic phase than those on the LaSrO-terminated La_0.67Sr_0.33MnO₃, while with no wake-up effect. Even though the Hf_0.5Zr_0.5O₂ thickness is as thin as 1.5 nm, the clear ferroelectric orthorhombic (111) orientation is observed on the MnO₂ termination. Our transmission electron microscopy characterization and theoretical modelling reveal that reconstruction at the Hf_0.5Zr_0.5O₂/ La_0.67Sr_0.33MnO₃ interface and hole doping of the Hf_0.5Zr_0.5O₂ layer resulting from the MnO₂ interface termination are responsible for the stabilization of the metastable ferroelectric phase of Hf_0.5Zr_0.5O₂. We anticipate that these results will inspire further studies of interface-engineered hafnia-based systems.