Epitaxial Strain Enhanced Ferroelectric Polarization toward a Giant Tunneling Electroresistance

Xiaoqi Li; Jiaqi Liu; Jianqi Huang; Biaohong Huang; Lingli Li; Yizhuo Li; Wentao Hu; Changji Li; Sajjad Ali; Teng Yang; Fei Xue; Zheng Han; Yun-Long Tang; Weijin Hu; Zhidong Zhang

doi:10.1021/acsnano.3c10933

Epitaxial Strain Enhanced Ferroelectric Polarization toward a Giant Tunneling Electroresistance

ACS Nano. 2024 Mar 19;18(11):7989-8001. doi: 10.1021/acsnano.3c10933. Epub 2024 Mar 4.

Authors

Xiaoqi Li^{1

2}, Jiaqi Liu^{1

2}, Jianqi Huang¹, Biaohong Huang^{1

2}, Lingli Li^{1

2}, Yizhuo Li¹, Wentao Hu^{1

2}, Changji Li¹, Sajjad Ali³, Teng Yang^{1

2}, Fei Xue⁴, Zheng Han^{5

6}, Yun-Long Tang^{1

2}, Weijin Hu^{1

2}, Zhidong Zhang¹

Affiliations

¹ Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
² School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China.
³ Energy, Water, and Environment Lab, College of Humanities and Sciences, Prince Sultan University, Riyadh 11586, Saudi Arabia.
⁴ ZJU-Hangzhou Global Scientific and Technological Innovation Center, School of Micro-Nano Electronics, Zhejiang University, Hangzhou 311215, China.
⁵ State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Optoelectronics, Shanxi University, Taiyuan 030006, China.
⁶ Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China.

PMID: 38438318
DOI: 10.1021/acsnano.3c10933

Abstract

A substantial ferroelectric polarization is the key for designing high-performance ferroelectric nonvolatile memories. As a promising candidate system, the BaTiO₃/La_0.67Sr_0.33MnO₃ (BTO/LSMO) ferroelectric/ferromagnetic heterostructure has attracted a lot of attention thanks to the merits of high Curie temperature, large spin polarization, and low ferroelectric coercivity. Nevertheless, the BTO/LSMO heterostructure suffers from a moderate FE polarization, primarily due to the quick film-thickness-driven strain relaxation. In response to this challenge, we propose an approach for enhancing the FE properties of BTO films by using a Sr₃Al₂O₆ (SAO) buffering layer to mitigate the interfacial strain relaxation. The continuously tunable strain allows us to illustrate the linear dependence of polarization on epitaxial strain with a large strain-sensitive coefficient of ∼27 μC/cm² per percent strain. This results in a giant polarization of ∼80 μC/cm² on the BTO/LSMO interface. Leveraging this large polarization, we achieved a giant tunneling electroresistance (TER) of ∼10⁵ in SAO-buffered Pt/BTO/LSMO ferroelectric tunnel junctions (FTJs). Our research uncovers the fundamental interplay between strain, polarization magnitude, and device performance, such as on/off ratio, thereby advancing the potential of FTJs for next-generation information storage applications.

Keywords: BaTiO3; Sr3Al2O6; epitaxial strain; ferroelectric tunnel junction; spontaneous polarization; strain-sensitive coefficient; tunneling electroresistance.