Atomic-scale fatigue mechanism of ferroelectric tunnel junctions

Yihao Yang; Ming Wu; Xingwen Zheng; Chunyan Zheng; Jibo Xu; Zhiyu Xu; Xiaofei Li; Xiaojie Lou; Di Wu; Xiaohui Liu; Stephen J Pennycook; Zheng Wen

doi:10.1126/sciadv.abh2716

Atomic-scale fatigue mechanism of ferroelectric tunnel junctions

Sci Adv. 2021 Nov 26;7(48):eabh2716. doi: 10.1126/sciadv.abh2716. Epub 2021 Nov 24.

Authors

Yihao Yang¹, Ming Wu^{2

3}, Xingwen Zheng⁴, Chunyan Zheng¹, Jibo Xu¹, Zhiyu Xu¹, Xiaofei Li¹, Xiaojie Lou², Di Wu⁵, Xiaohui Liu⁴, Stephen J Pennycook³, Zheng Wen¹

Affiliations

¹ College of Physics and Center for Marine Observation and Communications, Qingdao University, Qingdao 266071, China.
² State Key Laboratory of Electrical Insulation and Power Equipment and Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an 710049, China.
³ Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore.
⁴ School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Ji'nan 250100, China.
⁵ National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, Jiangsu Key Laboratory of Artificial Functional Materials and Collaborative Innovation Center for Advanced Materials, Nanjing University, Nanjing 210093, China.

Abstract

Ferroelectric tunnel junctions (FTJs) are promising candidates for next-generation memories due to fast read/write speeds and low-power consumptions. Here, we investigate resistance fatigue of FTJs, which is performed on Pt/BaTiO₃/Nb:SrTiO₃ devices. By direct observations of the 5–unit cell–thick BaTiO₃ barrier with high-angle annular dark-field imaging and electron energy loss spectroscopy, oxygen vacancies are found to aggregate at the Pt/BaTiO₃ interface during repetitive switching, leading to a ferroelectric dead layer preventing domain nucleation and growth. Severe oxygen deficiency also makes BaTiO₃ lattices energetically unfavorable and lastly induces a destruction of local perovskite structure of the barrier. Ferroelectric properties are thus degraded, which reduces barrier contrast between ON and OFF states and smears electroresistance characteristics of Pt/BaTiO₃/Nb:SrTiO₃ FTJs. These results reveal an atomic-scale fatigue mechanism of ultrathin ferroelectric barriers associated with the aggregation of charged defects, facilitating the design of reliable FTJs and ferroelectric nanoelectronic devices for practical applications.