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Hu W, Fan Z, Mo L, Lin H, Li M, Li W, Ou J, Tao R, Tian G, Qin M, Zeng M, Lu X, Zhou G, Gao X, Liu JM. Volatile Resistive Switching and Short-Term Synaptic Plasticity in a Ferroelectric-Modulated SrFeO x Memristor. ACS APPLIED MATERIALS & INTERFACES 2025; 17:9595-9605. [PMID: 39882776 DOI: 10.1021/acsami.4c19627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2025]
Abstract
SrFeOx (SFO) offers a topotactic phase transformation between an insulating brownmillerite SrFeO2.5 (BM-SFO) phase and a conductive perovskite SrFeO3 (PV-SFO) phase, making it a competitive candidate for use in resistive memory and neuromorphic computing. However, most of existing SFO-based memristors are nonvolatile devices which struggle to achieve short-term synaptic plasticity (STP). To address this issue and realize STP, we propose to leverage ferroelectric polarization to effectively draw ions across the interface so that the PV-SFO conductive filaments (CFs) can be ruptured in absence of an external field. As a proof of concept, we fabricate ferroelectric Pb(Zr0.2Ti0.8)O3 (PZT)/BM-SFO bilayer films with Au top electrodes and SrRuO3 bottom electrodes. The device exhibits the desired volatile resistive switching behavior, with its low resistance state decaying over time. Such volatility is attributed to the positive polarization charge near the PZT/SFO interface, which can attract the oxygen ions from SFO to PZT and hence lead to the rupture of CFs. Moreover, this volatile device successfully emulates STP-related synaptic functions, including excitatory postsynaptic current, paired-pulse facilitation, learning-experience behavior, associative learning, and reservoir computing. Our study showcases an effective method for achieving volatile resistive switching and STP, which may be applied to various systems beyond SFO-based memristors.
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Affiliation(s)
- Wenjie Hu
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Zhen Fan
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Linyuan Mo
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Haipeng Lin
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Meixia Li
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Wenjie Li
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Jiali Ou
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Ruiqiang Tao
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Guo Tian
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Minghui Qin
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Min Zeng
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Xubing Lu
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Guofu Zhou
- National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Xingsen Gao
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Jun-Ming Liu
- Institute for Advanced Materials and Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
- Laboratory of Solid State Microstructures and Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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2
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Su R, Chen D, Cheng W, Xiao R, Deng Y, Duan Y, Li Y, Ye L, An H, Xu J, Lai PT, Miao X. Oxygen Vacancy Compensation-Induced Analog Resistive Switching in the SrFeO 3-δ/Nb:SrTiO 3 Epitaxial Heterojunction for Noise-Tolerant High-Precision Image Recognition. ACS APPLIED MATERIALS & INTERFACES 2024; 16:54115-54128. [PMID: 39327975 DOI: 10.1021/acsami.4c07951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/28/2024]
Abstract
Neuromorphic computing, inspired by the brain's architecture, promises to surpass the limitations of von Neumann computing. In this paradigm, synaptic devices play a crucial role, with resistive switching memory (memristors) emerging as promising candidates due to their low power consumption and scalability advantages. This study focuses on the development of metal/oxide-semiconductor heterojunctions, which offer several technological advantages and have broad potential for applications in artificial neural synapses. However, constructing high-quality epitaxial interfaces between metal and oxide semiconductors and designing modifiable contact barriers are challenging. Herein, we construct high-quality epitaxial metal/semiconductor interfaces based on the metallicity of the perovskite phase SrFeO3-δ (PV-SFO) and a small Schottky barrier in contact with Nb-doped SrTiO3 (NSTO). X-ray diffraction patterns, reciprocal space mapping results, and cross-sectional transmission electron microscopy images reveal that the prepared PV-SFO film exhibits a perfect single-crystal structure and an excellent epitaxial interface with the NSTO (111) substrate. The corresponding memristor exhibits analog-type resistive-variable characteristics with an ON/OFF ratio of ∼1000, stable data retention after 10,000 s, and no noticeable fluctuation in resistance after 10,000 pulse cycles. Electron energy loss spectroscopy, first-principles calculations, and electrical measurements reveal that compensating or restoring oxygen vacancies at the NSTO surface decreases or increases the contact barrier between PV-SFO and NSTO, respectively, thereby gradually regulating the resistance value. Furthermore, high-quality epitaxial PV-SFO/NSTO devices achieve up to 98.21% recognition accuracy for handwriting recognition tasks using LeNet-5-based network structures and 92.21% accuracy for color images using visual geometry group (VGG) network structures. This work contributes to the advancement of interface-type memristors and provides valuable insights into enhancing synaptic functionality in neuromorphic computing systems.
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Affiliation(s)
- Rui Su
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan 430074, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong 999077, China
| | - Dunbao Chen
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Weiming Cheng
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Ruizi Xiao
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yuheng Deng
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong 999077, China
| | - Yufeng Duan
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yi Li
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Lei Ye
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Hongyu An
- College of New Materials and New Energies, Shenzhen Technology University, Shenzhen 518118, China
| | - Jingping Xu
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Peter To Lai
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong 999077, China
| | - Xiangshui Miao
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan 430074, China
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3
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Zhang R, Su R, Shen C, Xiao R, Cheng W, Miao X. Research Progress on the Application of Topological Phase Transition Materials in the Field of Memristor and Neuromorphic Computing. SENSORS (BASEL, SWITZERLAND) 2023; 23:8838. [PMID: 37960537 PMCID: PMC10650417 DOI: 10.3390/s23218838] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 10/07/2023] [Accepted: 10/27/2023] [Indexed: 11/15/2023]
Abstract
Topological phase transition materials have strong coupling between their charge, spin orbitals, and lattice structure, which makes them have good electrical and magnetic properties, leading to promising applications in the fields of memristive devices. The smaller Gibbs free energy difference between the topological phases, the stable oxygen vacancy ordered structure, and the reversible topological phase transition promote the memristive effect, which is more conducive to its application in information storage, information processing, information calculation, and other related fields. In particular, extracting the current resistance or conductance of the two-terminal memristor to convert to the weight of the synapse in the neural network can simulate the behavior of biological synapses in their structure and function. In addition, in order to improve the performance of memristors and better apply them to neuromorphic computing, methods such as ion doping, electrode selection, interface modulation, and preparation process control have been demonstrated in memristors based on topological phase transition materials. At present, it is considered an effective method to obtain a unique resistive switching behavior by improving the process of preparing functional layers, regulating the crystal phase of topological phase transition materials, and constructing interface barrier-dependent devices. In this review, we systematically expound the resistance switching mechanism, resistance switching performance regulation, and neuromorphic computing of topological phase transition memristors, and provide some suggestions for the challenges faced by the development of the next generation of non-volatile memory and brain-like neuromorphic devices based on topological phase transition materials.
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Affiliation(s)
| | | | | | | | - Weiming Cheng
- School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan 430074, China; (R.Z.); (R.S.); (C.S.); (R.X.); (X.M.)
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4
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Zhang F, Zhang Y, Li L, Mou X, Peng H, Shen S, Wang M, Xiao K, Ji SH, Yi D, Nan T, Tang J, Yu P. Nanoscale multistate resistive switching in WO 3 through scanning probe induced proton evolution. Nat Commun 2023; 14:3950. [PMID: 37402709 DOI: 10.1038/s41467-023-39687-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 06/22/2023] [Indexed: 07/06/2023] Open
Abstract
Multistate resistive switching device emerges as a promising electronic unit for energy-efficient neuromorphic computing. Electric-field induced topotactic phase transition with ionic evolution represents an important pathway for this purpose, which, however, faces significant challenges in device scaling. This work demonstrates a convenient scanning-probe-induced proton evolution within WO3, driving a reversible insulator-to-metal transition (IMT) at nanoscale. Specifically, the Pt-coated scanning probe serves as an efficient hydrogen catalysis probe, leading to a hydrogen spillover across the nano junction between the probe and sample surface. A positively biased voltage drives protons into the sample, while a negative voltage extracts protons out, giving rise to a reversible manipulation on hydrogenation-induced electron doping, accompanied by a dramatic resistive switching. The precise control of the scanning probe offers the opportunity to manipulate the local conductivity at nanoscale, which is further visualized through a printed portrait encoded by local conductivity. Notably, multistate resistive switching is successfully demonstrated via successive set and reset processes. Our work highlights the probe-induced hydrogen evolution as a new direction to engineer memristor at nanoscale.
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Affiliation(s)
- Fan Zhang
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, 100084, Beijing, China
- State Key Laboratory of Information Photonics and Optical Communications & School of Science, Beijing University of Posts and Telecommunications, 100876, Beijing, China
| | - Yang Zhang
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, 100084, Beijing, China
| | - Linglong Li
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, 100084, Beijing, China
| | - Xing Mou
- School of Integrated Circuits, Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, 100084, Beijing, China
| | - Huining Peng
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, 100084, Beijing, China
| | - Shengchun Shen
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, 100084, Beijing, China
| | - Meng Wang
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Kunhong Xiao
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, 100084, Beijing, China
| | - Shuai-Hua Ji
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, 100084, Beijing, China
- Frontier Science Center for Quantum Information, 100084, Beijing, China
| | - Di Yi
- State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, 100084, Beijing, China
| | - Tianxiang Nan
- School of Integrated Circuits, Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, 100084, Beijing, China
- Beijing Innovation Center for Future Chips (ICFC), Tsinghua University, 100084, Beijing, China
| | - Jianshi Tang
- School of Integrated Circuits, Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, 100084, Beijing, China
- Beijing Innovation Center for Future Chips (ICFC), Tsinghua University, 100084, Beijing, China
| | - Pu Yu
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, 100084, Beijing, China.
- Frontier Science Center for Quantum Information, 100084, Beijing, China.
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Zhao J, Chen K, Li SE, Zhang Q, Wang JO, Guo EJ, Qian H, Gu L, Qian T, Ibrahim K, Fan Z, Guo H. Electronic-structure evolution of SrFeO 3-xduring topotactic phase transformation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:064001. [PMID: 34740209 DOI: 10.1088/1361-648x/ac36fd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Accepted: 11/05/2021] [Indexed: 06/13/2023]
Abstract
Oxygen-vacancy-induced topotactic phase transformation between the ABO2.5brownmillerite structure and the ABO3perovskite structure attracts ever-increasing attention due to the perspective applications in catalysis, clean energy field, and memristors. However, a detailed investigation of the electronic-structure evolution during the topotactic phase transformation for understanding the underlying mechanism is highly desired. In this work, multiple analytical methods were used to explore evolution of the electronic structure of SrFeO3-xthin films during the topotactic phase transformation. The results indicate that the increase in oxygen content induces a new unoccupied state of O 2pcharacter near the Fermi energy, inducing the insulator-to-metal transition. More importantly, the hole states are more likely constrained to thedx2-y2orbital than to thed3z2-r2orbital. Our results reveal an unambiguous evolution of the electronic structure of SrFeO3-xfilms during topotactic phase transformation, which is crucial not only for fundamental understanding but also for perspective applications such as solid-state oxide fuel cells, catalysts, and memristor devices.
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Affiliation(s)
- Jiali Zhao
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Kaihui Chen
- Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, People's Republic of China
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, People's Republic of China
| | - Shi-En Li
- Key Laboratory of Material Physics, Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450052, People's Republic of China
| | - Qinghua Zhang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Jia-Ou Wang
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Er-Jia Guo
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
| | - Haijie Qian
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Lin Gu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
| | - Tian Qian
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
| | - Kurash Ibrahim
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Zhen Fan
- Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, People's Republic of China
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, People's Republic of China
| | - Haizhong Guo
- Key Laboratory of Material Physics, Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450052, People's Republic of China
- Collaborative Innovation Center of Light Manipulations and Applications, Shandong Normal University, Jinan 250358, People's Republic of China
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6
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Haselmann U, Suyolcu YE, Wu PC, Ivanov YP, Knez D, van Aken PA, Chu YH, Zhang Z. Negatively Charged In-Plane and Out-Of-Plane Domain Walls with Oxygen-Vacancy Agglomerations in a Ca-Doped Bismuth-Ferrite Thin Film. ACS APPLIED ELECTRONIC MATERIALS 2021; 3:4498-4508. [PMID: 34723187 PMCID: PMC8552442 DOI: 10.1021/acsaelm.1c00638] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 09/12/2021] [Indexed: 06/13/2023]
Abstract
The interaction of oxygen vacancies and ferroelectric domain walls is of great scientific interest because it leads to different domain-structure behaviors. Here, we use high-resolution scanning transmission electron microscopy to study the ferroelectric domain structure and oxygen-vacancy ordering in a compressively strained Bi0.9Ca0.1FeO3-δ thin film. It was found that atomic plates, in which agglomerated oxygen vacancies are ordered, appear without any periodicity between the plates in out-of-plane and in-plane orientation. The oxygen non-stoichiometry with δ ≈ 1 in FeO2-δ planes is identical in both orientations and shows no preference. Within the plates, the oxygen vacancies form 1D channels in a pseudocubic [010] direction with a high number of vacancies that alternate with oxygen columns with few vacancies. These plates of oxygen vacancies always coincide with charged domain walls in a tail-to-tail configuration. Defects such as ordered oxygen vacancies are thereby known to lead to a pinning effect of the ferroelectric domain walls (causing application-critical aspects, such as fatigue mechanisms and countering of retention failure) and to have a critical influence on the domain-wall conductivity. Thus, intentional oxygen vacancy defect engineering could be useful for the design of multiferroic devices with advanced functionality.
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Affiliation(s)
- Ulrich Haselmann
- Erich
Schmid Institute of Materials Science, Austrian
Academy of Sciences, Leoben 8700, Austria
| | - Y. Eren Suyolcu
- Department
of Materials Science and Engineering, Cornell
University, Ithaca, New York 14850, United States
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Ping-Chun Wu
- Department
of Materials Science and Engineering, National
Chiao Tung University, Hsinchu 30010, Taiwan
| | - Yurii P. Ivanov
- Erich
Schmid Institute of Materials Science, Austrian
Academy of Sciences, Leoben 8700, Austria
- Department
of Materials Science & Metallurgy, University
of Cambridge, Cambridge CB3 0FS, U.K.
- School of
Natural Sciences, Far Eastern Federal University, Vladivostok 690950, Russia
| | - Daniel Knez
- Graz
Centre for Electron Microscopy, Austrian
Cooperative Research, Graz 8010, Austria
| | - Peter A. van Aken
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Ying-Hao Chu
- Department
of Materials Science and Engineering, National
Chiao Tung University, Hsinchu 30010, Taiwan
| | - Zaoli Zhang
- Erich
Schmid Institute of Materials Science, Austrian
Academy of Sciences, Leoben 8700, Austria
- Institute
of Material Physics, Montanuniversität
Leoben, Leoben 8700, Austria
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7
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Alkali-deficiency driven charged out-of-phase boundaries for giant electromechanical response. Nat Commun 2021; 12:2841. [PMID: 33990584 PMCID: PMC8121868 DOI: 10.1038/s41467-021-23107-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 04/15/2021] [Indexed: 11/08/2022] Open
Abstract
Traditional strategies for improving piezoelectric properties have focused on phase boundary engineering through complex chemical alloying and phase control. Although they have been successfully employed in bulk materials, they have not been effective in thin films due to the severe deterioration in epitaxy, which is critical to film properties. Contending with the opposing effects of alloying and epitaxy in thin films has been a long-standing issue. Herein we demonstrate a new strategy in alkali niobate epitaxial films, utilizing alkali vacancies without alloying to form nanopillars enclosed with out-of-phase boundaries that can give rise to a giant electromechanical response. Both atomically resolved polarization mapping and phase field simulations show that the boundaries are strained and charged, manifesting as head-head and tail-tail polarization bound charges. Such charged boundaries produce a giant local depolarization field, which facilitates a steady polarization rotation between the matrix and nanopillars. The local elastic strain and charge manipulation at out-of-phase boundaries, demonstrated here, can be used as an effective pathway to obtain large electromechanical response with good temperature stability in similar perovskite oxides. Phase boundary engineering through chemical alloying and phase control is a traditional approach to enhancing piezoelectric properties. Here, the authors design a strategy in alkali niobate films, utilizing alkali vacancies without alloying to form nanopillars enclosed.
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