1
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Seo J, Lee H, Eom K, Byun J, Min T, Lee J, Lee K, Eom CB, Oh SH. Feld-induced modulation of two-dimensional electron gas at LaAlO 3/SrTiO 3 interface by polar distortion of LaAlO 3. Nat Commun 2024; 15:5268. [PMID: 38902225 PMCID: PMC11189907 DOI: 10.1038/s41467-024-48946-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 05/19/2024] [Indexed: 06/22/2024] Open
Abstract
Since the discovery of two-dimensional electron gas at the LaAlO3/SrTiO3 interface, its intriguing physical properties have garnered significant interests for device applications. Yet, understanding its response to electrical stimuli remains incomplete. Our in-situ transmission electron microscopy analysis of a LaAlO3/SrTiO3 two-dimensional electron gas device under electrical bias reveals key insights. Inline electron holography visualized the field-induced modulation of two-dimensional electron gas at the interface, while electron energy loss spectroscopy showed negligible electromigration of oxygen vacancies. Instead, atom-resolved imaging indicated that electric fields trigger polar distortion in the LaAlO3 layer, affecting two-dimensional electron gas modulation. This study refutes the previously hypothesized role of oxygen vacancies, underscoring the lattice flexibility of LaAlO3 and its varied polar distortions under electric fields as central to two-dimensional electron gas dynamics. These findings open pathways for advanced oxide nanoelectronics, exploiting the interplay of polar and nonpolar distortions in LaAlO3.
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Affiliation(s)
- Jinsol Seo
- Department of Energy Engineering, KENTECH Institute for Energy Materials and Devices, Korea Institute of Energy Technology (KENTECH), Naju, Republic of Korea
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Energy Systems Research and Department of Physics, Ajou University, Suwon, Republic of Korea
| | - Kitae Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jinho Byun
- Department of Energy Engineering, KENTECH Institute for Energy Materials and Devices, Korea Institute of Energy Technology (KENTECH), Naju, Republic of Korea
| | - Taewon Min
- Department of Physics, Pusan National University, Busan, Republic of Korea
| | - Jaekwang Lee
- Department of Physics, Pusan National University, Busan, Republic of Korea
| | - Kyoungjun Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Sang Ho Oh
- Department of Energy Engineering, KENTECH Institute for Energy Materials and Devices, Korea Institute of Energy Technology (KENTECH), Naju, Republic of Korea.
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2
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Li Y, Huang Y, Liu X, Wang Y, Yuan L. Density functional theory study on the formation mechanism and electrical properties of two-dimensional electron gas in biaxial-strained LaGaO 3 /BaSnO 3 heterostructure. Sci Rep 2024; 14:10259. [PMID: 38704471 DOI: 10.1038/s41598-024-60893-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Accepted: 04/29/2024] [Indexed: 05/06/2024] Open
Abstract
The two-dimensional electron gas (2DEG) in BaSnO3 -based heterostructure (HS) has received tremendous attention in the electronic applications because of its excellent electron migration characteristic. We modeled the n-type (LaO)+ /(SnO2 )0 interface by depositing LaGaO3 film on the BaSnO3 substrate and explored strain effects on the critical thickness for forming 2DEG and electrical properties of LaGaO3 /BaSnO3 HS system using first-principles electronic structure calculations. The results indicate that to form 2DEG in the unstrained LaGaO3 /BaSnO3 HS system, a minimum thickness of approximately 4 unit cells of LaGaO3 film is necessary. An increased film thickness of LaGaO3 is required to form the 2DEG for -3%-biaxially-strained HS system and the critical thickness is 3 unit cells for 3%-baxially-strained HS system, which is caused by the strain-induced change of the electrostatic potential in LaGaO3 film. In addition, the biaxial strain plays an important role in tailoring the electrical properties of 2DEG in LaGaO3 /BaSnO3 HS syestem. The interfacial charge carrier density, electron mobility and electrical conductivity can be optimized when a moderate tensile strain is applied on the BaSnO3 substrate in the ab-plane.
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Affiliation(s)
- Yuling Li
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University, Chengdu, 610039, People's Republic of China
| | - Yuxi Huang
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University, Chengdu, 610039, People's Republic of China
| | - Xiaohua Liu
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University, Chengdu, 610039, People's Republic of China
| | - Yaqin Wang
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University, Chengdu, 610039, People's Republic of China.
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China.
| | - Le Yuan
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University, Chengdu, 610039, People's Republic of China
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3
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Huang J, Dai S, Xu C, Du Y, Xu Z, Han K, Xu L, Wu W, Chen P, Huang Z. Capping-layer-mediated lattice mismatch and redox reaction in SrTiO 3-based bilayers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 35. [PMID: 37059113 DOI: 10.1088/1361-648x/accd37] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 04/14/2023] [Indexed: 05/16/2023]
Abstract
It is well known that the traditional two-dimensional electron system (2DES) hosted by the SrTiO3substrate can exhibit diverse electronic states by modifying the capping layer in heterostructures. However, such capping layer engineering is less studied in the SrTiO3-layer-carried 2DES (or bilayer 2DES), which is different from the traditional one on transport properties but more applicable to the thin-film devices. Here, several SrTiO3bilayers are fabricated by growing various crystalline and amorphous oxide capping layers on the epitaxial SrTiO3layers. For the crystalline bilayer 2DES, the monotonical reduction on the interfacial conductance, as well as carrier mobility, is recorded on increasing the lattice mismatch between the capping layers and epitaxial SrTiO3layer. The mobility edge raised by the interfacial disorders is highlighted in the crystalline bilayer 2DES. On the other hand, when increasing the concentration of Al with high oxygen affinity in the capping layer, the amorphous bilayer 2DES becomes more conductive accompanied by the enhanced carrier mobility but almost constant carrier density. This observation cannot be explained by the simple redox-reaction model, and the interfacial charge screening and band bending need to be considered. Moreover, when the capping oxide layers have the same chemical composition but with different forms, the crystalline 2DES with a large lattice mismatch is more insulating than its amorphous counterpart, and vice versa. Our results shed some light on understanding the different dominant role in forming the bilayer 2DES using crystalline and amorphous oxide capping layer, which may be applicable in designing other functional oxide interfaces.
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Affiliation(s)
- Jingwen Huang
- Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, People's Republic of China
| | - Song Dai
- Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, People's Republic of China
| | - Chengcheng Xu
- Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, People's Republic of China
| | - Yongyi Du
- Stony Brook Institute at Anhui University, Anhui University, Hefei 230039, People's Republic of China
| | - Zhipeng Xu
- Stony Brook Institute at Anhui University, Anhui University, Hefei 230039, People's Republic of China
| | - Kun Han
- Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, People's Republic of China
| | - Liqiang Xu
- Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, People's Republic of China
| | - Wenbin Wu
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Pingfan Chen
- Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, People's Republic of China
| | - Zhen Huang
- Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, People's Republic of China
- Stony Brook Institute at Anhui University, Anhui University, Hefei 230039, People's Republic of China
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4
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Fang L, Aggoune W, Ren W, Draxl C. How a Ferroelectric Layer Can Tune a Two-Dimensional Electron Gas at the Interface of LaInO 3 and BaSnO 3: A First-Principles Study. ACS APPLIED MATERIALS & INTERFACES 2023; 15:11314-11323. [PMID: 36787465 DOI: 10.1021/acsami.2c21886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The emerging interest in two-dimensional electron gases (2DEGs), formed at interfaces between two insulating oxide perovskites, poses a crucial fundamental question in view of future electronic devices. In the framework of density-functional theory, we investigate the possibility to control the characteristics of the 2DEG formed at the LaInO3/BaSnO3 interface by including a ferroelectric layer. To do so, we consider BaTiO3 as a prototype example and examine how the orientation of the ferroelectric polarization impacts density and confinement of the 2DEG. We find that aligning the ferroelectric polarization toward (outward) the LaInO3/BaSnO3 interface leads to an accumulation (depletion) of the interfacial 2DEG. Varying its magnitude, we find a linear effect on the 2DEG charge density that is confined within the BaSnO3 side. Analysis of the optimized geometries reveals that inclusion of the ferroelectric layer makes structural distortions at the LaInO3/BaSnO3 junction less pronounced, which, in turn, enhances the 2DEG density. Thicker ferroelectric layers allow for reaching higher polarization magnitude. We discuss the mechanisms behind all these findings and rationalize how the characteristics of both 2DEGs and 2D hole gases can be controlled in the considered heterostructures. Overall, our results can be generalized to other combinations of ferroelectric, polar, and nonpolar materials.
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Affiliation(s)
- Le Fang
- State Key Laboratory of Advanced Special Steel, School of Materials Science and Engineering, ICQMS and Physics Department, Shanghai University, Shanghai, 200444, China
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 12489, Germany
| | - Wahib Aggoune
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 12489, Germany
| | - Wei Ren
- State Key Laboratory of Advanced Special Steel, School of Materials Science and Engineering, ICQMS and Physics Department, Shanghai University, Shanghai, 200444, China
- Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University, Shanghai, 200444, China
| | - Claudia Draxl
- Institut für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 12489, Germany
- European Theoretical Spectroscopy Facility (ETSF), https://www.etsf.eu/
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5
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Kwak Y, Han W, Lee JS, Song J, Kim J. Hysteretic temperature dependence of resistance controlled by gate voltage in LaAlO 3/SrTiO 3 heterointerface electron system. Sci Rep 2022; 12:6458. [PMID: 35440752 PMCID: PMC9019089 DOI: 10.1038/s41598-022-10425-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 04/07/2022] [Indexed: 11/29/2022] Open
Abstract
For two-dimensional electron gas device applications, it is important to understand how electrical-transport properties are controlled by gate voltage. Here, we report gate voltage-controllable hysteresis in the resistance–temperature characteristics of two-dimensional electron gas at LaAlO3/SrTiO3 heterointerface. Electron channels made of the LaAlO3/SrTiO3 heterointerface showed hysteretic resistance–temperature behavior: the measured resistance was significantly higher during upward temperature sweeps in thermal cycling tests. Such hysteretic behavior was observed only after application of positive back-gate voltages below 50 K in the thermal cycle, and the magnitude of hysteresis increased with the applied back-gate voltage. To explain this gate-controlled resistance hysteresis, we propose a mechanism based on electron trapping at impurity sites, in conjunction with the strong temperature-dependent dielectric constant of the SrTiO3 substrate. Our model explains well the observed gate-controlled hysteresis of the resistance–temperature characteristics, and the mechanism should be also applicable to other SrTiO3-based oxide systems, paving the way to applications of oxide heterostructures to electronic devices.
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Affiliation(s)
- Yongsu Kwak
- Korea Research Institute of Standards and Science, Daejeon, 34113, South Korea.,Department of Physics, Chungnam National University, Daejeon, 34134, South Korea
| | - Woojoo Han
- Korea Research Institute of Standards and Science, Daejeon, 34113, South Korea.,Department of Nanoscience, University of Science and Technology, Daejeon, 34113, South Korea
| | - Joon Sung Lee
- Display and Semiconductor Physics, Korea University Sejong Campus, Sejong, 30019, South Korea
| | - Jonghyun Song
- Department of Physics, Chungnam National University, Daejeon, 34134, South Korea. .,Institute of Quantum Systems (IQS), Chungnam National University, Daejeon, 34134, South Korea.
| | - Jinhee Kim
- Korea Research Institute of Standards and Science, Daejeon, 34113, South Korea.
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6
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Prakash DJ, Chen Y, Debasu ML, Savage DE, Tangpatjaroen C, Deneke C, Malachias A, Alfieri AD, Elleuch O, Lekhal K, Szlufarska I, Evans PG, Cavallo F. Reconfiguration of Amorphous Complex Oxides: A Route to a Broad Range of Assembly Phenomena, Hybrid Materials, and Novel Functionalities. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2105424. [PMID: 34786844 DOI: 10.1002/smll.202105424] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 10/09/2021] [Indexed: 06/13/2023]
Abstract
Reconfiguration of amorphous complex oxides provides a readily controllable source of stress that can be leveraged in nanoscale assembly to access a broad range of 3D geometries and hybrid materials. An amorphous SrTiO3 layer on a Si:B/Si1- x Gex :B heterostructure is reconfigured at the atomic scale upon heating, exhibiting a change in volume of ≈2% and accompanying biaxial stress. The Si:B/Si1- x Gex :B bilayer is fabricated by molecular beam epitaxy, followed by sputter deposition of SrTiO3 at room temperature. The processes yield a hybrid oxide/semiconductor nanomembrane. Upon release from the substrate, the nanomembrane rolls up and has a curvature determined by the stress in the epitaxially grown Si:B/Si1- x Gex :B heterostructure. Heating to 600 °C leads to a decrease of the radius of curvature consistent with the development of a large compressive biaxial stress during the reconfiguration of SrTiO3 . The control of stresses via post-deposition processing provides a new route to the assembly of complex-oxide-based heterostructures in 3D geometry. The reconfiguration of metastable mechanical stressors enables i) synthesis of various types of strained superlattice structures that cannot be fabricated by direct growth and ii) technologies based on strain engineering of complex oxides via highly scalable lithographic processes and on large-area semiconductor substrates.
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Affiliation(s)
- Divya J Prakash
- Center for High Technology Materials, University of New Mexico, Albuquerque, NM, 87106, USA
- Department of Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Yajin Chen
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Mengistie L Debasu
- Center for High Technology Materials, University of New Mexico, Albuquerque, NM, 87106, USA
| | - Donald E Savage
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Chaiyapat Tangpatjaroen
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Christoph Deneke
- Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, Campinas, SP, 13083-970, Brazil
| | - Angelo Malachias
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil
| | - Adam D Alfieri
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Omar Elleuch
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Kaddour Lekhal
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Izabela Szlufarska
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Paul G Evans
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Francesca Cavallo
- Center for High Technology Materials, University of New Mexico, Albuquerque, NM, 87106, USA
- Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, NM, 87131, USA
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7
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Le OK, Chihaia V, Hong Hoa PT, Hai PT, Son DN. Physical insights into the Au growth on the surface of a LaAlO 3/SrTiO 3 heterointerface. RSC Adv 2022; 12:24146-24155. [PMID: 36128543 PMCID: PMC9403709 DOI: 10.1039/d2ra04038g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 08/10/2022] [Indexed: 11/21/2022] Open
Abstract
Au growth on the LAO/STO substrate generates an optical peak in the wavelength region of 600–1200 nm due to the interaction of the Au s and dz2 orbitals with the O pz orbital of the LAO film.
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Affiliation(s)
- Ong Kim Le
- Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam
- Vietnam National University Ho Chi Minh City, Linh Trung Ward, Ho Chi Minh City, Vietnam
| | - Viorel Chihaia
- Institute of Physical Chemistry “Ilie Murgulescu” of the Romanian Academy, Splaiul Independentei 202, Sector 6, 060021 Bucharest, Romania
| | - Phan Thi Hong Hoa
- Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam
- Vietnam National University Ho Chi Minh City, Linh Trung Ward, Ho Chi Minh City, Vietnam
| | - Pham Thanh Hai
- Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam
- Vietnam National University Ho Chi Minh City, Linh Trung Ward, Ho Chi Minh City, Vietnam
| | - Do Ngoc Son
- Ho Chi Minh City University of Technology (HCMUT), 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam
- Vietnam National University Ho Chi Minh City, Linh Trung Ward, Ho Chi Minh City, Vietnam
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8
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Tokuda Y, Irimoto T, Nishikawa N, Katsuyama Y, Kobayashi S, Tokunaga T, Yamamoto T. Direct determination of a topmost atomic layer of (100) surfaces on (La
0.3
Sr
0.7
)(Al
0.65
Ta
0.35
)O
3
single crystals annealed in air by high‐resolution scanning transmission electron microscopy. SURF INTERFACE ANAL 2021. [DOI: 10.1002/sia.7043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Yoshinori Tokuda
- Department of Materials Design Innovation Engineering Nagoya University Nagoya Japan
| | - Takeshi Irimoto
- Department of Materials Design Innovation Engineering Nagoya University Nagoya Japan
| | - Naoki Nishikawa
- Department of Materials Design Innovation Engineering Nagoya University Nagoya Japan
| | - Yutaro Katsuyama
- Department of Materials Design Innovation Engineering Nagoya University Nagoya Japan
| | - Shunsuke Kobayashi
- Nanostructures Research Laboratory Japan Fine Ceramics Center Nagoya Japan
| | - Tomoharu Tokunaga
- Department of Materials Design Innovation Engineering Nagoya University Nagoya Japan
| | - Takahisa Yamamoto
- Department of Materials Design Innovation Engineering Nagoya University Nagoya Japan
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9
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Sun B, Zhou G, Sun L, Zhao H, Chen Y, Yang F, Zhao Y, Song Q. ABO 3 multiferroic perovskite materials for memristive memory and neuromorphic computing. NANOSCALE HORIZONS 2021; 6:939-970. [PMID: 34652346 DOI: 10.1039/d1nh00292a] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The unique electron spin, transfer, polarization and magnetoelectric coupling characteristics of ABO3 multiferroic perovskite materials make them promising candidates for application in multifunctional nanoelectronic devices. Reversible ferroelectric polarization, controllable defect concentration and domain wall movement originated from the ABO3 multiferroic perovskite materials promotes its memristive effect, which further highlights data storage, information processing and neuromorphic computing in diverse artificial intelligence applications. In particular, ion doping, electrode selection, and interface modulation have been demonstrated in ABO3-based memristive devices for ultrahigh data storage, ultrafast information processing, and efficient neuromorphic computing. These approaches presented today including controlling the dopant in the active layer, altering the oxygen vacancy distribution, modulating the diffusion depth of ions, and constructing the interface-dependent band structure were believed to be efficient methods for obtaining unique resistive switching (RS) behavior for various applications. In this review, internal physical dynamics, preparation technologies, and modulation methods are systemically examined as well as the progress, challenges, and possible solutions are proposed for next generation emerging ABO3-based memristive application in artificial intelligence.
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Affiliation(s)
- Bai Sun
- School of Physical Science and Technology, Key Laboratory of Advanced Technology of Materials (Ministry of Education of China), Southwest Jiaotong University, Chengdu, Sichuan 610031, China.
- Superconductivity and New Energy R&D Center, Southwest Jiaotong University, Chengdu, Sichuan 610031, China
| | - Guangdong Zhou
- School of Artificial Intelligence and School of Materials and Energy, Southwest University, Chongqing 400715, China.
| | - Linfeng Sun
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Hongbin Zhao
- State Key Laboratory of Advanced Materials for Smart Sensing, General Research Institute for Nonferrous Metals, Beijing, 100088, China
| | - Yuanzheng Chen
- School of Physical Science and Technology, Key Laboratory of Advanced Technology of Materials (Ministry of Education of China), Southwest Jiaotong University, Chengdu, Sichuan 610031, China.
| | - Feng Yang
- Superconductivity and New Energy R&D Center, Southwest Jiaotong University, Chengdu, Sichuan 610031, China
| | - Yong Zhao
- School of Physical Science and Technology, Key Laboratory of Advanced Technology of Materials (Ministry of Education of China), Southwest Jiaotong University, Chengdu, Sichuan 610031, China.
- Superconductivity and New Energy R&D Center, Southwest Jiaotong University, Chengdu, Sichuan 610031, China
| | - Qunliang Song
- School of Artificial Intelligence and School of Materials and Energy, Southwest University, Chongqing 400715, China.
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10
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Eom K, Yu M, Seo J, Yang D, Lee H, Lee JW, Irvin P, Oh SH, Levy J, Eom CB. Electronically reconfigurable complex oxide heterostructure freestanding membranes. SCIENCE ADVANCES 2021; 7:7/33/eabh1284. [PMID: 34389541 PMCID: PMC8363151 DOI: 10.1126/sciadv.abh1284] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 06/24/2021] [Indexed: 05/28/2023]
Abstract
In recent years, lanthanum aluminate/strontium titanate (LAO/STO) heterointerfaces have been used to create a growing family of nanoelectronic devices based on nanoscale control of LAO/STO metal-to-insulator transition. The properties of these devices are wide-ranging, but they are restricted by nature of the underlying thick STO substrate. Here, single-crystal freestanding membranes based on LAO/STO heterostructures were fabricated, which can be directly integrated with other materials via van der Waals stacking. The key properties of LAO/STO are preserved when LAO/STO membranes are formed. Conductive atomic force microscope lithography is shown to successfully create reversible patterns of nanoscale conducting regions, which survive to millikelvin temperatures. The ability to form reconfigurable conducting nanostructures on LAO/STO membranes opens opportunities to integrate a variety of nanoelectronics with silicon-based architectures and flexible, magnetic, or superconducting materials.
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Affiliation(s)
- Kitae Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Muqing Yu
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Jinsol Seo
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Dengyu Yang
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jung-Woo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Sang Ho Oh
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA.
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA.
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11
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Sohn W, Kim TL, Lee TH, Yoon S, Kim C, Yoo JW, Roh KC, Kim M, Jang HW. Suppression of metal-to-insulator transition using strong interfacial coupling at cubic and orthorhombic perovskite oxide heterointerfaces. NANOSCALE 2021; 13:708-715. [PMID: 33367436 DOI: 10.1039/d0nr07545k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
A quasi-two-dimensional electron gas (2DEG) evolved at the LaAlO3 (LAO)/SrTiO3 (STO) interface has attracted significant attention, because the insertion of perovskite titanates can tune the 2DEG conductivity. However, this depends on the Ti-O-Ti bonding angle and structural symmetry. In this study, we controlled the octahedral tilt of the LAO/CaTiO3 (CTO) interface by heterostructuring it with CTO grown on STO substrates of various thicknesses. The 2DEG was maintained when the thickness of CTO was below the critical thickness of 5 unit cells (uc); however, it was suppressed when the CTO thickness was above the critical thickness. High-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) combined with integrated differential phase contrast (iDPC) STEM imaging was used to visualize the TiO6 octahedral tilt propagation and symmetry of the 5 uc and 24 uc CTO films. The symmetry of the 5 uc CTO film resembled that of the STO substrate, whereas the octahedral tilt propagated in the 24 uc CTO film due to the structural relaxation. These results show that the interface engineering of the octahedral tilt can enable or suppress the formation of the 2DEG in perovskite oxides.
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Affiliation(s)
- Woonbae Sohn
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea and Energy Storage Materials Centre, Korea Institute of Ceramic Engineering and Technology, Jinju 52851, Republic of Korea
| | - Taemin Ludvic Kim
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea
| | - Tae Hyung Lee
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea
| | - Sangmoon Yoon
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea
| | - Chungsoo Kim
- Technology of Analysis Centre, Korea Institute of Ceramic Engineering and Technology, Jinju 52851, Republic of Korea
| | - Jung-Woo Yoo
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
| | - Kwang Chul Roh
- Energy Storage Materials Centre, Korea Institute of Ceramic Engineering and Technology, Jinju 52851, Republic of Korea
| | - Miyoung Kim
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea
| | - Ho Won Jang
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea
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12
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Ding J, Cheng J, Dogan F, Li Y, Lin W, Yao Y, Manchon A, Yang K, Wu T. Two-Dimensional Electron Gas at the Spinel/Perovskite Interface: Suppression of Polar Catastrophe by an Ultrathin Layer of Interfacial Defects. ACS APPLIED MATERIALS & INTERFACES 2020; 12:42982-42991. [PMID: 32829635 DOI: 10.1021/acsami.0c13337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Two-dimensional electron gas (2DEG) at the interface between two insulating perovskite oxides has attracted much interest for both fundamental physics and potential applications. Here, we report the discovery of a new 2DEG formed at the interface between spinel MgAl2O4 and perovskite SrTiO3. Transport measurements, electron microscopy imaging, and first-principles calculations reveal that the interfacial 2DEG is closely related to the symmetry breaking at the MgAl2O4/SrTiO3 interface. The critical film thickness for the insulator-to-metal transition is approximately 32 Å, which is twice as thick as that reported on the widely studied LaAlO3/SrTiO3 system. Scanning transmission electron microscopy imaging indicates the formation of interfacial Ti-Al antisite defects with a thickness of ∼4 Å. First-principles density functional theory calculations indicate that the coexistence of the antisite defects and surface oxygen vacancies may explain the formation of interfacial 2DEG as well as the observed critical film thickness. The discovery of 2DEG at the spinel/perovskite interface introduces a new material platform for designing oxide interfaces with desired characteristics.
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Affiliation(s)
- Junfeng Ding
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
| | - Jianli Cheng
- Department of NanoEngineering, University of California, San Diego, La Jolla, California 92093-0448, United States
| | - Fatih Dogan
- College of Engineering and Technology, American University of the Middle East, Kuwait
| | - Yangyang Li
- Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore
| | - Weinan Lin
- Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore
| | - Yingbang Yao
- School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, People's Republic of China
| | - Aurelien Manchon
- Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
- Aix-Marseille Univ, CNRS, CINaM, Marseille 13288, France
| | - Kesong Yang
- Department of NanoEngineering, University of California, San Diego, La Jolla, California 92093-0448, United States
| | - Tom Wu
- School of Materials Science and Engineering, University of New South Wales (UNSW), Sydney, NSW 2052, Australia
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13
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Ain QU, Naseem S, Nazir S. Robust half-metallicity and magnetic phase transition in Sr 2CrReO 6 via strain engineering. Sci Rep 2020; 10:13778. [PMID: 32792535 PMCID: PMC7426967 DOI: 10.1038/s41598-020-70768-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 07/23/2020] [Indexed: 12/02/2022] Open
Abstract
Using ab-initio calculations, the electronic and magnetic properties of double perovskite oxide \documentclass[12pt]{minimal}
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\begin{document}$${\text{Sr}}_2 {\text{CrReO}}_6$$\end{document}Sr2CrReO6 with two type of strains: biaxial (along the [110]-direction) and hydrostatic (along [111]-direction) are investigated. The ground state of the unstrained system is half-metallic ferrimagnetic, due to a strong antiferromagnetic (AFM) coupling between Cr and Re atoms within both (GGA and GGA+U) exchange-correlation potentials. It is demonstrated that the robustness of half-metallicity can be preserved under the influence of both biaxial and hydrostatic strains. Interestingly, a transition from ferri-to-ferromagnetic is established due to Re spin flipping to that of the Cr ion (i.e. Cr and Re spin becomes parallel) within the GGA+U method for both biaxial and hydrostatic tensile strains of \documentclass[12pt]{minimal}
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\begin{document}$$\ge +2\%$$\end{document}≥+2%. The strong confinement of orbitals due to tensile strain results in the decrease of electron hopping which further reduced the AFM coupling strength between Cr and Re atoms, this leads to a ferri-to-ferromagnetic transition. However, the GGA scheme holds the ferrimagnetic state with both kinds of strains. This work shows that tensile strain is a feasible way to optimize the magnetic properties of perovskite oxides, which are presumed to be beneficial for spintronic technology.
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Affiliation(s)
- Qurat-Ul Ain
- Department of Physics, University of Sargodha, Sargodha, 40100, Pakistan
| | - Shahnila Naseem
- Department of Physics, University of Sargodha, Sargodha, 40100, Pakistan
| | - Safdar Nazir
- Department of Physics, University of Sargodha, Sargodha, 40100, Pakistan.
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14
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Kim JM, Cho C, Hsieh EY, Nam S. Heterogeneous deformation of two-dimensional materials for emerging functionalities. JOURNAL OF MATERIALS RESEARCH 2020; 35:1369-1385. [PMID: 32572304 PMCID: PMC7306914 DOI: 10.1557/jmr.2020.34] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Atomically thin 2D materials exhibit strong intralayer covalent bonding and weak interlayer van der Waals interactions, offering unique high in-plane strength and out-of-plane flexibility. While atom-thick nature of 2D materials may cause uncontrolled intrinsic/extrinsic deformation in multiple length scales, it also provides new opportunities for exploring coupling between heterogeneous deformations and emerging functionalities in controllable and scalable ways for electronic, optical, and optoelectronic applications. In this review, we discuss (i) the mechanical characteristics of 2D materials, (ii) uncontrolled inherent deformation and extrinsic heterogeneity present in 2D materials, (iii) experimental strategies for controlled heterogeneous deformation of 2D materials, (iv) 3D structure-induced novel functionalities via crumple/wrinkle structure or kirigami structures, and (v) heterogeneous strain-induced emerging functionalities in exciton and phase engineering. Overall, heterogeneous deformation offers unique advantages for 2D materials research by enabling spatial tunability of 2D materials' interactions with photons, electrons, and molecules in a programmable and controlled manner.
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Affiliation(s)
- Jin Myung Kim
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Chullhee Cho
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Ezekiel Y. Hsieh
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - SungWoo Nam
- Department of Materials Science and Engineering, Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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15
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Chen Q, Dwyer C, Sheng G, Zhu C, Li X, Zheng C, Zhu Y. Imaging Beam-Sensitive Materials by Electron Microscopy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1907619. [PMID: 32108394 DOI: 10.1002/adma.201907619] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 12/20/2019] [Indexed: 05/15/2023]
Abstract
Electron microscopy allows the extraction of multidimensional spatiotemporally correlated structural information of diverse materials down to atomic resolution, which is essential for figuring out their structure-property relationships. Unfortunately, the high-energy electrons that carry this important information can cause damage by modulating the structures of the materials. This has become a significant problem concerning the recent boost in materials science applications of a wide range of beam-sensitive materials, including metal-organic frameworks, covalent-organic frameworks, organic-inorganic hybrid materials, 2D materials, and zeolites. To this end, developing electron microscopy techniques that minimize the electron beam damage for the extraction of intrinsic structural information turns out to be a compelling but challenging need. This article provides a comprehensive review on the revolutionary strategies toward the electron microscopic imaging of beam-sensitive materials and associated materials science discoveries, based on the principles of electron-matter interaction and mechanisms of electron beam damage. Finally, perspectives and future trends in this field are put forward.
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Affiliation(s)
- Qiaoli Chen
- Center for Electron Microscopy, State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology and College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, 310014, China
| | - Christian Dwyer
- Department of Physics, Arizona State University, Tempe, AZ, 85287-1504, USA
| | - Guan Sheng
- Advanced Membranes and Porous Materials Center, Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Chongzhi Zhu
- Center for Electron Microscopy, State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology and College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, 310014, China
| | - Xiaonian Li
- Center for Electron Microscopy, State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology and College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, 310014, China
| | - Changlin Zheng
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai, 200438, China
| | - Yihan Zhu
- Center for Electron Microscopy, State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology and College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, 310014, China
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16
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Gunnink PM, Bouwmeester RL, Brinkman A. Artificial oxide heterostructures with non-trivial topology. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:085601. [PMID: 33176291 DOI: 10.1088/1361-648x/abc973] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In the quest for topological insulators with large band gaps, heterostructures with Rashba spin-orbit interactions come into play. Transition metal oxides with heavy ions are especially interesting in this respect. We discuss the design principles for stacking oxide Rashba layers. Assuming a single layer with a two-dimensional electron gas (2DEG) on both interfaces as a building block, a two-dimensional topological insulating phase is present when negative coupling between the 2DEGs exists. When stacking multiple building blocks, a two-dimensional or three-dimensional topological insulator is artificially created, depending on the intra- and interlayer coupling strengths and the number of building blocks. We show that the three-dimensional topological insulator is protected by reflection symmetry, and can therefore be classified as a topological crystalline insulator. In order to isolate the topological states from bulk states, the intralayer coupling term needs to be quadratic in momentum. It is described how such a quadratic coupling could potentially be realized by taking buckling within the layers into account. The buckling, thereby, brings the idea of stacked Rashba system very close to the alternative approach of realizing the buckled honeycomb lattice in [111]-oriented perovskite oxides.
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Affiliation(s)
- Pieter M Gunnink
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
| | - Rosa Luca Bouwmeester
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
| | - Alexander Brinkman
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
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17
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Li L, Xie L, Pan X. Real-time studies of ferroelectric domain switching: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2019; 82:126502. [PMID: 31185460 DOI: 10.1088/1361-6633/ab28de] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Ferroelectric materials have been utilized in a broad range of electronic, optical, and electromechanical applications and hold the promise for the design of future high-density nonvolatile memories and multifunctional nano-devices. The applications of ferroelectric materials stem from the ability to switch polarized domains by applying an electric field, and therefore a fundamental understanding of the switching dynamics is critical for design of practical devices. In this review, we summarize the progress in the study of the microscopic process of ferroelectric domain switching using recently developed in situ transmission electron microscopy (TEM). We first briefly introduce the instrumentation, experimental procedures, imaging mechanisms, and analytical methods of the state-of-the-art in situ TEM techniques. The application of these techniques to studying a wide range of complex switching phenomena, including domain nucleation, domain wall motion, domain relaxation, domain-defect interaction, and the interplay between different types of domains, is demonstrated. The underlying physics of these dynamic processes are discussed.
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Affiliation(s)
- Linze Li
- Department of Materials Science and Engineering, University of California, Irvine, CA 92697, United States of America
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18
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Yang Q, Tao L, Zhang Y, Li M, Jiang Z, Tsymbal EY, Alexandrov V. Ferroelectric Tunnel Junctions Enhanced by a Polar Oxide Barrier Layer. NANO LETTERS 2019; 19:7385-7393. [PMID: 31514498 DOI: 10.1021/acs.nanolett.9b03056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Ferroelectric tunnel junctions (FTJs) have recently aroused significant interest due to the interesting physics controlling their properties and potential application in nonvolatile memory devices. In this work, we propose a new concept to design high-performance FTJs based on ferroelectric/polar-oxide composite barriers. Using density functional theory calculations, we model electronic and transport properties of LaNiO3/PbTiO3/LaAlO3/LaNiO3 tunnel junctions and demonstrate that an ultrathin polar LaAlO3(001) layer strongly enhances their performance. We predict a tunneling electroresistance (TER) effect in these FTJs with an OFF/ON resistance ratio exceeding a factor of 104 and ON state resistance as low as about 1 kΩμm2. Such an enhanced performance is driven by the ionic charge at the PbTiO3/LaAlO3 interface, which significantly increases transmission across the FTJ when the ferroelectric polarization of PbTiO3 is pointing against the intrinsic electric field produced by this ionic charge. This is due to the formation of a two-dimensional (2D) electron or hole gas, depending on the LaAlO3 termination being (LaO)+ or (AlO2)-, respectively, which is formed to screen the polarization charge of the nonuniform polarization state. This 2D electron (hole) gas can be switched ON and OFF by the reversal of ferroelectric polarization, resulting in the giant TER effect. The proposed design suggests a new direction for creating FTJs with a stable and reversible ferroelectric polarization, a sizable TER effect, and a low-resistance-area product, as required for memory applications.
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Affiliation(s)
- Qiong Yang
- Department of Chemical and Biomolecular Engineering , University of Nebraska , Lincoln , Nebraska 68588 , United States
- School of Materials Science and Engineering , Xiangtan University , Xiangtan , Hunan 411105 , China
| | - Lingling Tao
- Department of Physics and Astronomy , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Yuke Zhang
- School of Materials Science and Engineering , Xiangtan University , Xiangtan , Hunan 411105 , China
| | - Ming Li
- Department of Physics and Astronomy , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Zhen Jiang
- Department of Chemical and Biomolecular Engineering , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Vitaly Alexandrov
- Department of Chemical and Biomolecular Engineering , University of Nebraska , Lincoln , Nebraska 68588 , United States
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19
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Kim TL, Choi MJ, Lee TH, Sohn W, Jang HW. Tailoring of Interfacial Band Offsets by an Atomically Thin Polar Insulating Layer To Enhance the Water-Splitting Performance of Oxide Heterojunction Photoanodes. NANO LETTERS 2019; 19:5897-5903. [PMID: 31095915 DOI: 10.1021/acs.nanolett.9b01431] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
An important factor in the performance of photoelectrochemical water splitting is the band edge alignment of the photoelectrodes for efficient transport and transfer of photogenerated carriers. Many studies for improving charge transfer ability between the electrode and the electrolyte have been reported, while research to improve charge transfer at the interface of the photoactive semiconductor and the conducting substrate is largely lacking. Here, we demonstrate that the water-splitting performance of an oxide heterostructured photoelectrode can be increased 6-fold by inserting an atomically thin polar LaAlO3 interlayer compared with that of an oxide heterostructure without an insertion to modify interfacial band offsets. The electrically lowered Schottky barrier is driven by the atomically thin layer, and the charge transfer resistance between the oxides is reduced by up to 2 orders of magnitude upon insertion of LaAlO3, a wide-gap (5.6 eV) insulator. We show that the critical thickness of the polar layer for enhancing the charge transfer is 3 unit cells. The dipole moment from the polar sheets of LaAlO3 introduces an internal electric field, which modifies the effective band offsets in the device. This work serves as a proof of concept that photoelectrochemical performance can be improved by manipulating the band offsets of the heterostructure interface, suggesting a new design strategy for heterostructured water-splitting photoelectrodes.
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Affiliation(s)
- Taemin Ludvic Kim
- Department of Materials Science and Engineering, Research Institute of Advanced Materials , Seoul National University , Seoul 08826 , Republic of Korea
| | - Min-Ju Choi
- Department of Materials Science and Engineering, Research Institute of Advanced Materials , Seoul National University , Seoul 08826 , Republic of Korea
| | - Tae Hyung Lee
- Department of Materials Science and Engineering, Research Institute of Advanced Materials , Seoul National University , Seoul 08826 , Republic of Korea
| | - Woonbae Sohn
- Department of Materials Science and Engineering, Research Institute of Advanced Materials , Seoul National University , Seoul 08826 , Republic of Korea
| | - Ho Won Jang
- Department of Materials Science and Engineering, Research Institute of Advanced Materials , Seoul National University , Seoul 08826 , Republic of Korea
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20
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Zhang F, Lv P, Zhang Y, Huang S, Wong CM, Yau HM, Chen X, Wen Z, Jiang X, Zeng C, Hong J, Dai JY. Modulating the Electrical Transport in the Two-Dimensional Electron Gas at LaAlO_{3}/SrTiO_{3} Heterostructures by Interfacial Flexoelectricity. PHYSICAL REVIEW LETTERS 2019; 122:257601. [PMID: 31347866 DOI: 10.1103/physrevlett.122.257601] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 04/12/2019] [Indexed: 06/10/2023]
Abstract
Thin film flexoelectricity is attracting more attention because of its enhanced effect and potential application in electronic devices. Here we find that a mechanical bending induced flexoelectricity significantly modulates the electrical transport properties of the interfacial two-dimensional electron gas (2DEG) at the LaAlO_{3}/SrTiO_{3} (LAO/STO) heterostructure. Under variant bending states, both the carrier density and mobility of the 2DEG are changed according to the flexoelectric polarization direction, showing an electric field effect modulation. By measuring the flexoelectric response of LAO, it is found that the effective flexoelectricity in the LAO thin film is enhanced by 3 orders compared to its bulk. These results broaden the horizon of study on the flexoelectricity effect in the hetero-oxide interface and more research on the oxide interfacial flexoelectricity may be stimulated.
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Affiliation(s)
- Fan Zhang
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, 27606, USA
| | - Peng Lv
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing, 100081, People's Republic of China
| | - Yiteng Zhang
- College of Physics, Qingdao University, Qingdao, 266071, China
| | - Shujin Huang
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, 27606, USA
| | - Chi-Man Wong
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
| | - Hei-Man Yau
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
| | - Xinxin Chen
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
| | - Zheng Wen
- College of Physics, Qingdao University, Qingdao, 266071, China
| | - Xiaoning Jiang
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, 27606, USA
| | - Changgan Zeng
- International Center for Quantum Design of Functional Materials, Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Strongly Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, 230026, China
| | - Jiawang Hong
- School of Aerospace Engineering, Beijing Institute of Technology, Beijing, 100081, People's Republic of China
| | - Ji-Yan Dai
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, 999077 Kowloon, Hong Kong
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21
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Wang Y, Sui R, Bi M, Tang W, Ma S. Strain sensitivity of band structure and electron mobility in perovskite BaSnO 3: first-principles calculation. RSC Adv 2019; 9:14072-14077. [PMID: 35519295 PMCID: PMC9064022 DOI: 10.1039/c9ra02146a] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 04/11/2019] [Indexed: 12/04/2022] Open
Abstract
A first-principles electronic structure calculation is utilized to contrastively investigate the crystal structure, band structure, electron effective mass and mobility of perovskite BaSnO3 under hydrostatic and biaxial strain. Strain-induced changes in relative properties are remarkable and more sensitive to hydrostatic strain than biaxial strain. The structure of BaSnO3 remains cubic under hydrostatic strain, while it becomes tetragonal under biaxial strain. Originating from the strain sensitivity of the Sn 5s orbitals in the conduction band minimum, the band gaps of BaSnO3 decrease for both types of strain from -3% to 3%. BaSnO3 under tensile hydrostatic strain exhibits higher electron mobility than it does under tensile biaxial strain because of the smaller electron effective mass in the corresponding strain. In contrast, the opposite phenomenon exists in compressive strain. Our results demonstrate that strain could be an alternative way to modify the band gap and electron mobility of BaSnO3.
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Affiliation(s)
- Yaqin Wang
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University Chengdu 610039 China
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China Chengdu 610054 China
| | - Runqing Sui
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University Chengdu 610039 China
| | - Mei Bi
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University Chengdu 610039 China
| | - Wu Tang
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China Chengdu 610054 China
| | - Sude Ma
- Key Laboratory of Fluid and Power Machinery, School of Material Science and Engineering, Xihua University Chengdu 610039 China
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22
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Biswas A, Talha M, Kashir A, Jeong YH. A thin film perspective on quantum functional oxides. CURRENT APPLIED PHYSICS 2019; 19:207-214. [DOI: 10.1016/j.cap.2018.07.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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23
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Chen L, Sutton E, Lee H, Lee JW, Li J, Eom CB, Irvin P, Levy J. Over 100-THz bandwidth selective difference frequency generation at LaAlO 3/SrTiO 3 nanojunctions. LIGHT, SCIENCE & APPLICATIONS 2019; 8:24. [PMID: 30820320 PMCID: PMC6393436 DOI: 10.1038/s41377-019-0135-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 02/01/2019] [Accepted: 02/02/2019] [Indexed: 06/09/2023]
Abstract
The ability to combine continuously tunable narrow-band terahertz (THz) generation that can access both the far-infrared and mid-infrared regimes with nanometer-scale spatial resolution is highly promising for identifying underlying light-matter interactions and realizing selective control of rotational or vibrational resonances in nanoparticles or molecules. Here, we report selective difference frequency generation with over 100 THz bandwidth via femtosecond optical pulse shaping. The THz emission is generated at nanoscale junctions at the interface of LaAlO3/SrTiO3 (LAO/STO) that is defined by conductive atomic force microscope lithography, with the potential to perform THz spectroscopy on individual nanoparticles or molecules. Numerical simulation of the time-domain signal facilitates the identification of components that contribute to the THz generation. This ultra-wide-bandwidth tunable nanoscale coherent THz source transforms the LAO/STO interface into a promising platform for integrated lab-on-chip optoelectronic devices with various functionalities.
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Affiliation(s)
- Lu Chen
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 USA
- Pittsburgh Quantum Institute, Pittsburgh, PA 15260 USA
| | - Erin Sutton
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 USA
- Pittsburgh Quantum Institute, Pittsburgh, PA 15260 USA
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WA 53706 USA
| | - Jung-Woo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WA 53706 USA
| | - Jianan Li
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 USA
- Pittsburgh Quantum Institute, Pittsburgh, PA 15260 USA
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WA 53706 USA
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 USA
- Pittsburgh Quantum Institute, Pittsburgh, PA 15260 USA
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 USA
- Pittsburgh Quantum Institute, Pittsburgh, PA 15260 USA
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24
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Wang L, Pan W, Hu WX, Sun DY. Strain-induced indirect-to-direct bandgap transition in an np-type LaAlO 3/SrTiO 3(110) superlattice. Phys Chem Chem Phys 2019; 21:7075-7082. [DOI: 10.1039/c8cp07761d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
By applying uniaxial in-plane strains, an indirect-to-direct bandgap transition occurs in the polar LaAlO3/SrTiO3 (110) superlattices.
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Affiliation(s)
- L. Wang
- Department of Physics
- East China Normal University
- Shanghai 200241
- People's Republic of China
| | - W. Pan
- Department of Physics
- East China Normal University
- Shanghai 200241
- People's Republic of China
| | - W. X. Hu
- The computer Center
- East China Normal University
- Shanghai 200241
- People's Republic of China
| | - D. Y. Sun
- Department of Physics
- East China Normal University
- Shanghai 200241
- People's Republic of China
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25
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Huang Z, Renshaw Wang X, Rusydi A, Chen J, Yang H, Venkatesan T. Interface Engineering and Emergent Phenomena in Oxide Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1802439. [PMID: 30133012 DOI: 10.1002/adma.201802439] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 07/06/2018] [Indexed: 06/08/2023]
Abstract
Complex oxide interfaces have mesmerized the scientific community in the last decade due to the possibility of creating tunable novel multifunctionalities, which are possible owing to the strong interaction among charge, spin, orbital, and structural degrees of freedom. Artificial interfacial modifications, which include defects, formal polarization, structural symmetry breaking, and interlayer interaction, have led to novel properties in various complex oxide heterostructures. These emergent phenomena not only serve as a platform for investigating strong electronic correlations in low-dimensional systems but also provide potentials for exploring next-generation electronic devices with high functionality. Herein, some recently developed strategies in engineering functional oxide interfaces and their emergent properties are reviewed.
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Affiliation(s)
- Zhen Huang
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Xiao Renshaw Wang
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Andrivo Rusydi
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Jingsheng Chen
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Hyunsoo Yang
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Thirumalai Venkatesan
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
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26
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Chemically specific termination control of oxide interfaces via layer-by-layer mean inner potential engineering. Nat Commun 2018; 9:2965. [PMID: 30054461 PMCID: PMC6063925 DOI: 10.1038/s41467-018-04903-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 05/25/2018] [Indexed: 11/16/2022] Open
Abstract
Creating oxide interfaces with precise chemical specificity at the atomic layer level is desired for the engineering of quantum phases and electronic applications, but highly challenging, owing partially to the lack of in situ tools to monitor the chemical composition and completeness of the surface layer during growth. Here we report the in situ observation of atomic layer-by-layer inner potential variations by analysing the Kikuchi lines during epitaxial growth of strontium titanate, providing a powerful real-time technique to monitor and control the chemical composition during growth. A model combining the effects of mean inner potential and step edge density (roughness) reveals the underlying mechanism of the complex and previously not well-understood reflection high-energy electron diffraction oscillations observed in the shuttered growth of oxide films. General rules are proposed to guide the synthesis of atomically and chemically sharp oxide interfaces, opening up vast opportunities for the exploration of intriguing quantum phenomena at oxide interfaces. Precisely controlled growth of oxide interfaces at the atomic layer level is critical for device applications but quite challenging. Here Sun et al. show real time monitoring and control of the surface composition of epitaxial strontium titanate perovskite films by analysing the Kikuchi lines.
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27
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Chen L, Li J, Tang Y, Pai YY, Chen Y, Pryds N, Irvin P, Levy J. Extreme Reconfigurable Nanoelectronics at the CaZrO 3 /SrTiO 3 Interface. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1801794. [PMID: 29962024 DOI: 10.1002/adma.201801794] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 05/10/2018] [Indexed: 06/08/2023]
Abstract
Complex oxide heterostructures have fascinating emergent properties that originate from the properties of the bulk constituents as well as from dimensional confinement. The conductive behavior of the polar/nonpolar LaAlO3 /SrTiO3 interface can be reversibly switched using conductive atomic force microscopy (c-AFM) lithography, enabling a wide range of devices and physics to be explored. Here, extreme nanoscale control over the CaZrO3 /SrTiO3 (CZO/STO) interface, which is formed from two materials that are both nonpolar, is reported. Nanowires with measured widths as narrow as 1.2 nm are realized at the CZO/STO interface at room temperature by c-AFM lithography. These ultrathin nanostructures have spatial dimensions at room temperature that are comparable to single-walled carbon nanotubes, and hold great promise for alternative oxide-based nanoelectronics, as well as offer new opportunities to investigate the electronic structure of the complex oxide interfaces. The cryogenic properties of devices constructed from quasi-1D channels, tunnel barriers, and planar gates exhibit gate-tunable superconductivity, quantum oscillations, electron pairing outside of the superconducting regime, and quasi-ballistic transport. This newly demonstrated ability to control the metal-insulator transition at nonpolar oxide interface greatly expands the class of materials whose behavior can be patterned and reconfigured at extreme nanoscale dimensions.
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Affiliation(s)
- Lu Chen
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Jianan Li
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Yuhe Tang
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Yun-Yi Pai
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Yunzhong Chen
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, Roskilde, 4000, Denmark
| | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, Roskilde, 4000, Denmark
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
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28
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Jnawali G, Lee H, Lee JW, Huang M, Hsu JF, Bi F, Zhou R, Cheng G, D'Urso B, Irvin P, Eom CB, Levy J. Graphene-Complex-Oxide Nanoscale Device Concepts. ACS NANO 2018; 12:6128-6136. [PMID: 29750506 DOI: 10.1021/acsnano.8b02457] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The integration of graphene with complex-oxide heterostructures such as LaAlO3/SrTiO3 offers the opportunity to combine the multifunctional properties of an oxide interface with the exceptional electronic properties of graphene. The ability to control interface conduction through graphene and understanding how it affects the intrinsic properties of an oxide interface are critical to the technological development of multifunctional devices. Here we demonstrate several device archetypes in which electron transport at an oxide interface is modulated using a patterned graphene top-gate. Nanoscale devices are fabricated at the oxide interface by conductive atomic force microscope (c-AFM) lithography, and transport measurements are performed as a function of the graphene gate voltage. Experiments are performed with devices written adjacent to or directly underneath the graphene gate. Distinct capabilities of this approach include the ability to create highly flexible device configurations, the ability to modulate carrier density at the oxide interface, and the ability to control electron transport up to the single-electron tunneling regime, while maintaining intrinsic transport properties of the oxide interface. Our results facilitate the design of a variety of nanoscale devices that combine excellent transport properties of these two proximal two-dimensional electron systems.
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Affiliation(s)
- Giriraj Jnawali
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Hyungwoo Lee
- Department of Materials Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Jung-Woo Lee
- Department of Materials Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Mengchen Huang
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Jen-Feng Hsu
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Feng Bi
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Rongpu Zhou
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Guanglei Cheng
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
- CAS Key Laboratory of Microscale Magnetic Resonance and Department of Modern Physics , University of Science and Technology of China , Hefei 230026 , China
| | - Brian D'Urso
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Patrick Irvin
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
| | - Chang-Beom Eom
- Department of Materials Science and Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States
| | - Jeremy Levy
- Department of Physics and Astronomy , University of Pittsburgh , Pittsburgh 15260 , United States
- Pittsburgh Quantum Institute , Pittsburgh , Pennsylvania 15260 , United States
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29
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Baiutti F, Gregori G, Suyolcu YE, Wang Y, Cristiani G, Sigle W, van Aken PA, Logvenov G, Maier J. High-temperature superconductivity at the lanthanum cuprate/lanthanum-strontium nickelate interface. NANOSCALE 2018; 10:8712-8720. [PMID: 29701210 DOI: 10.1039/c8nr00885j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The utilization of interface effects in epitaxial systems at the nanoscale has emerged as a very powerful approach for engineering functional properties of oxides. Here we present a novel structure fabricated by a state-of-the-art oxide molecular beam epitaxy method and consisting of lanthanum cuprate and strontium (Sr)-doped lanthanum nickelate, in which interfacial high-temperature superconductivity (Tc up to 40 K) occurs at the contact between the two phases. In such a system, we are able to tune the superconducting properties simply by changing the structural parameters. By employing electron spectroscopy and microscopy combined with dedicated conductivity measurements, we show that decoupling occurs between the electronic charge carrier and the cation (Sr) concentration profiles at the interface and that a hole accumulation layer forms, which dictates the resulting superconducting properties. Such effects are rationalized in the light of a generalized space-charge theory for oxide systems that takes account of both ionic and electronic redistribution effects.
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Affiliation(s)
- F Baiutti
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany.
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30
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Alsubaie A, Sharma P, Lee JH, Kim JY, Yang CH, Seidel J. Uniaxial Strain-Controlled Ferroelastic Domain Evolution in BiFeO 3. ACS APPLIED MATERIALS & INTERFACES 2018; 10:11768-11775. [PMID: 29557167 DOI: 10.1021/acsami.8b01711] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We investigate the effect of variable uniaxial tensile strain on the evolution of 71° ferroelastic domains in (001)-oriented epitaxial BiFeO3 (BFO) thin films using piezoresponse force microscopy (PFM). For this purpose, a newly designed bending stage has been employed, which allows tensile bending as wells as in situ PFM characterization. In situ PFM imaging reveals polarization-strain correlations at the nanoscale. Specifically, ferroelastic domains with in-plane polarization along the direction of applied tensile strain expand, whereas the adjoining domains with orthogonal in-plane polarization contract. The switching is mediated by significant domain wall roughening and opposite displacement of the successive walls. Further, the domains with long-range order are more susceptible to an applied external mechanical stimulus compared to the domains, which exhibit short-range periodicity. In addition, the imprint state of film reverses direction under applied tensile strain. Finally, the strain-induced changes in the domain structure and wall motion are fully reversible and revert to their as-grown state upon release of the applied stress. The strain-induced non-180° polarization rotation constitutes a route to control connected functionalities, such as magnetism, via coupled in-plane rotation of the magnetic plane in multiferroic BFO thin films.
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Affiliation(s)
- Abdullah Alsubaie
- School of Materials Science and Engineering , UNSW Sydney , Sydney , NSW 2052 , Australia
- School of Physics , Taif University , Taif 26571 , Kingdom of Saudi Arabia
| | - Pankaj Sharma
- School of Materials Science and Engineering , UNSW Sydney , Sydney , NSW 2052 , Australia
| | - Jin Hong Lee
- Unité Mixte de Physique , CNRS, Thales, Université Paris Sud, Université Paris-Saclay , 91767 Palaiseau , France
| | | | | | - Jan Seidel
- School of Materials Science and Engineering , UNSW Sydney , Sydney , NSW 2052 , Australia
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31
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Lee H, Campbell N, Lee J, Asel TJ, Paudel TR, Zhou H, Lee JW, Noesges B, Seo J, Park B, Brillson LJ, Oh SH, Tsymbal EY, Rzchowski MS, Eom CB. Direct observation of a two-dimensional hole gas at oxide interfaces. NATURE MATERIALS 2018; 17:231-236. [PMID: 29403056 DOI: 10.1038/s41563-017-0002-4] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Accepted: 11/27/2017] [Indexed: 06/07/2023]
Abstract
The discovery of a two-dimensional electron gas (2DEG) at the LaAlO3/SrTiO3 interface 1 has resulted in the observation of many properties2-5 not present in conventional semiconductor heterostructures, and so become a focal point for device applications6-8. Its counterpart, the two-dimensional hole gas (2DHG), is expected to complement the 2DEG. However, although the 2DEG has been widely observed 9 , the 2DHG has proved elusive. Herein we demonstrate a highly mobile 2DHG in epitaxially grown SrTiO3/LaAlO3/SrTiO3 heterostructures. Using electrical transport measurements and in-line electron holography, we provide direct evidence of a 2DHG that coexists with a 2DEG at complementary heterointerfaces in the same structure. First-principles calculations, coherent Bragg rod analysis and depth-resolved cathodoluminescence spectroscopy consistently support our finding that to eliminate ionic point defects is key to realizing a 2DHG. The coexistence of a 2DEG and a 2DHG in a single oxide heterostructure provides a platform for the exciting physics of confined electron-hole systems and for developing applications.
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Affiliation(s)
- H Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - N Campbell
- Department of Physics, University of Wisconsin-Madison, Madison, WI, USA
| | - J Lee
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea
| | - T J Asel
- Department of Physics, The Ohio State University, Columbus, OH, USA
| | - T R Paudel
- Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - H Zhou
- X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, USA
| | - J W Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - B Noesges
- Department of Physics, The Ohio State University, Columbus, OH, USA
| | - J Seo
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea
| | - B Park
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Korea
| | - L J Brillson
- Department of Physics, The Ohio State University, Columbus, OH, USA
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, USA
| | - S H Oh
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea
| | - E Y Tsymbal
- Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - M S Rzchowski
- Department of Physics, University of Wisconsin-Madison, Madison, WI, USA
| | - C B Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA.
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32
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Pai YY, Tylan-Tyler A, Irvin P, Levy J. Physics of SrTiO 3-based heterostructures and nanostructures: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2018; 81:036503. [PMID: 29424362 DOI: 10.1088/1361-6633/aa892d] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
This review provides a summary of the rich physics expressed within SrTiO3-based heterostructures and nanostructures. The intended audience is researchers who are working in the field of oxides, but also those with different backgrounds (e.g., semiconductor nanostructures). After reviewing the relevant properties of SrTiO3 itself, we will then discuss the basics of SrTiO3-based heterostructures, how they can be grown, and how devices are typically fabricated. Next, we will cover the physics of these heterostructures, including their phase diagram and coupling between the various degrees of freedom. Finally, we will review the rich landscape of quantum transport phenomena, as well as the devices that elicit them.
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Affiliation(s)
- Yun-Yi Pai
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, United States of America. Pittsburgh Quantum Institute, Pittsburgh, PA 15260, United States of America
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33
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Wang S, Bai Y, Xie L, Li C, Key JD, Wu D, Wang P, Pan X. Ferroelectric Polarization-Modulated Interfacial Fine Structures Involving Two-Dimensional Electron Gases in Pb(Zr,Ti)O 3/LaAlO 3/SrTiO 3 Heterostructures. ACS APPLIED MATERIALS & INTERFACES 2018; 10:1374-1382. [PMID: 29226675 DOI: 10.1021/acsami.7b14712] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Interfacial fine structures of bare LaAlO3/SrTiO3 (LAO/STO) heterostructures are compared with those of LAO/STO heterostructures capped with upward-polarized Pb(Zr0.1,Ti0.9)O3 (PZTup) or downward-polarized Pb(Zr0.5,Ti0.5)O3 (PZTdown) overlayers by aberration-corrected scanning transmission electron microscopy experiments. By combining the acquired electron energy-loss spectroscopy mapping, we are able to directly observe electron transfer from Ti4+ to Ti3+ and ionic displacements at the interface of bare LAO/STO and PZTdown/LAO/STO heterostructure unit cell by unit cell. No evidence of Ti3+ is observed at the interface of the PZTup/LAO/STO samples. Furthermore, the confinement of the two-dimensional electron gas (2DEG) at the interface is determined by atomic-column spatial resolution. Compared with the bare LAO/STO interface, the 2DEG density at the LAO/STO interface is enhanced or depressed by the PZTdown or PZTup overlayer, respectively. Our microscopy studies shed light on the mechanism of ferroelectric modulation of interfacial transport at polar/nonpolar oxide heterointerfaces, which may facilitate applications of these materials as nonvolatile memory.
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Affiliation(s)
- Shuangbao Wang
- National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
- Collaborative Innovation Center of Sustainable Energy Materials, Guangxi University , Nanning 530004, China
| | - Yuhang Bai
- National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Lin Xie
- National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Chen Li
- National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Julian D Key
- Collaborative Innovation Center of Sustainable Energy Materials, Guangxi University , Nanning 530004, China
| | - Di Wu
- National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Peng Wang
- National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China
| | - Xiaoqing Pan
- Department of Physics and Astronomy and Department of Chemical Engineering and Materials Science, University of California , Irvine, California 92697, United States
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34
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Li CJ, Xue HX, Qu GL, Shen SC, Hong YP, Wang XX, Liu MR, Jiang WM, Badica P, He L, Dou RF, Xiong CM, Lü WM, Nie JC. Influence of In-Gap States on the Formation of Two-Dimensional Election Gas at ABO 3/SrTiO 3 Interfaces. Sci Rep 2018; 8:195. [PMID: 29317754 PMCID: PMC5760580 DOI: 10.1038/s41598-017-18583-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 12/13/2017] [Indexed: 12/01/2022] Open
Abstract
We explored in-gap states (IGSs) in perovskite oxide heterojunction films. We report that IGSs in these films play a crucial role in determining the formation and properties of interfacial two-dimensional electron gas (2DEG). We report that electron trapping by IGSs opposes charge transfer from the film to the interface. The IGS in films yielded insulating interfaces with polar discontinuity and explained low interface carrier density of conducting interfaces. An ion trapping model was proposed to explain the physics of the IGSs and some experimental findings, such as the unexpected formation of 2DEG at the initially insulating LaCrO3/SrTiO3 interface and the influence of substitution layers on 2DEG.
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Affiliation(s)
- Cheng-Jian Li
- Department of Physics, Beijing Normal University, Beijing, 100875, China
| | - Hong-Xia Xue
- Department of Physics, Beijing Normal University, Beijing, 100875, China
| | - Guo-Liang Qu
- Department of Physics, Beijing Normal University, Beijing, 100875, China
| | - Sheng-Chun Shen
- Department of Physics, Beijing Normal University, Beijing, 100875, China
| | - Yan-Peng Hong
- Department of Physics, Beijing Normal University, Beijing, 100875, China
| | - Xin-Xin Wang
- Department of Physics, Beijing Normal University, Beijing, 100875, China
| | - Ming-Rui Liu
- Department of Physics, Beijing Normal University, Beijing, 100875, China
| | - Wei-Min Jiang
- Department of Physics, Beijing Normal University, Beijing, 100875, China
| | - Petre Badica
- National Institute of Materials Physics, Atomistilor 405A, Magurele, Ilfov, 077125, Romania
| | - Lin He
- Department of Physics, Beijing Normal University, Beijing, 100875, China
| | - Rui-Fen Dou
- Department of Physics, Beijing Normal University, Beijing, 100875, China
| | - Chang-Min Xiong
- Department of Physics, Beijing Normal University, Beijing, 100875, China
| | - Wei-Ming Lü
- Condensed Matter Science and Technology Institute, Harbin Institute of Technology, Harbin, 150001, China
| | - Jia-Cai Nie
- Department of Physics, Beijing Normal University, Beijing, 100875, China.
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35
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Eom K, Choi E, Yoon J, Choi M, Song K, Choi SY, Lee D, Lee JW, Eom CB, Lee J. Electron-Lattice Coupling in Correlated Materials of Low Electron Occupancy. NANO LETTERS 2017; 17:5458-5463. [PMID: 28850246 DOI: 10.1021/acs.nanolett.7b02109] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In correlated materials including transition metal oxides, electronic properties and functionalities are modulated and enriched by couplings between the electron and lattice degrees of freedom. These couplings are controlled by external parameters such as chemical doping, pressure, magnetic and electric fields, and light irradiation. However, the electron-lattice coupling relies on orbital characters, i.e., symmetry and occupancy, of t2g and eg orbitals, so that a large electron-lattice coupling is limited to eg electron system, whereas t2g electron system exhibits an inherently weak coupling. Here, we design and demonstrate a strongly enhanced electron-lattice coupling in electron-doped SrTiO3, that is, the t2g electron system. In ultrathin films of electron-doped SrTiO3 [i.e., (La0.25Sr0.75)TiO3], we reveal the strong electron-lattice-orbital coupling, which is manifested by extremely increased tetragonality and the corresponding metal-to-insulator transition. Our findings open the way of an active tuning of the charge-lattice-orbital coupling to obtain new functionalities relevant to emerging nanoelectronic devices.
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Affiliation(s)
- Kitae Eom
- School of Advanced Materials Science and Engineering, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Euiyoung Choi
- School of Advanced Materials Science and Engineering, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Jonghyun Yoon
- School of Advanced Materials Science and Engineering, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Minsu Choi
- School of Advanced Materials Science and Engineering, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Kyung Song
- Department of Materials Modeling and Characterization, Korea Institute of Materials Science , Changwon 51508, Republic of Korea
| | - Si-Young Choi
- Department of Materials Modeling and Characterization, Korea Institute of Materials Science , Changwon 51508, Republic of Korea
| | - Daesu Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53792, United States
| | - Jung-Woo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53792, United States
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53792, United States
| | - Jaichan Lee
- School of Advanced Materials Science and Engineering, Sungkyunkwan University , Suwon 16419, Republic of Korea
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36
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Li L, Zhang Y, Xie L, Jokisaari JR, Beekman C, Yang JC, Chu YH, Christen HM, Pan X. Atomic-Scale Mechanisms of Defect-Induced Retention Failure in Ferroelectrics. NANO LETTERS 2017; 17:3556-3562. [PMID: 28471679 DOI: 10.1021/acs.nanolett.7b00696] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The ability to switch the ferroelectric polarization using an electric field makes ferroelectrics attractive for application in nanodevices such as high-density memories. One of the major challenges impeding this application, however, has been known as "retention failure", which is a spontaneous process of polarization back-switching that can lead to data loss. This process is generally thought to be caused by the domain instability arising from interface boundary conditions and countered by defects, which can pin the domain wall and impede the back-switching. Here, using in situ transmission electron microscopy and atomic-scale scanning transmission electron microscopy, we show that the polarization retention failure can be induced by commonly observed nanoscale impurity defects in BiFeO3 thin films. The interaction between polarization and the defects can also lead to the stabilization of novel functional nanodomains with mixed-phase structures and head-to-head polarization configurations. Thus, defect engineering provides a new route for tuning properties of ferroelectric nanosystems.
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Affiliation(s)
- Linze Li
- Department of Chemical Engineering and Materials Science, University of California - Irvine , Irvine, California 92697, United States
| | - Yi Zhang
- Department of Chemical Engineering and Materials Science, University of California - Irvine , Irvine, California 92697, United States
| | - Lin Xie
- Department of Chemical Engineering and Materials Science, University of California - Irvine , Irvine, California 92697, United States
- National Laboratory of Solid State Microstructures and College of Engineering and Applied Sciences, Nanjing University , Nanjing, Jiangsu 210093, China
| | - Jacob R Jokisaari
- Department of Materials Science and Engineering, University of Michigan , Ann Arbor, Michigan 48109, United States
| | - Christianne Beekman
- Materials Science and Technology Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - Jan-Chi Yang
- Department of Physics, National Cheng Kung University , Tainan 701, Taiwan
| | - Ying-Hao Chu
- Department of Materials Science and Engineering, National Chiao Tung University , Hsinchu 300, Taiwan
| | - Hans M Christen
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
| | - Xiaoqing Pan
- Department of Chemical Engineering and Materials Science, University of California - Irvine , Irvine, California 92697, United States
- Department of Physics and Astronomy, University of California - Irvine , Irvine, California 92697, United States
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37
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Jnawali G, Huang M, Hsu JF, Lee H, Lee JW, Irvin P, Eom CB, D'Urso B, Levy J. Room-Temperature Quantum Transport Signatures in Graphene/LaAlO 3 /SrTiO 3 Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1603488. [PMID: 28042885 DOI: 10.1002/adma.201603488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 10/23/2016] [Indexed: 06/06/2023]
Abstract
High mobility graphene field-effect devices, fabricated on the complex-oxide heterostructure LaAlO3 /SrTiO3 , exhibit quantum interference signatures up to room temperature. The oxide material is believed to play a critical role in suppressing short-range and phonon contributions to scattering. The ability to maintain pseudospin coherence at room temperature holds promise for the realization of new classical and quantum information technologies.
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Affiliation(s)
- Giriraj Jnawali
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Mengchen Huang
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Jen-Feng Hsu
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Jung-Woo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Brian D'Urso
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, PA, 15260, USA
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38
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Cheng J, Luo J, Yang K. Comparison Studies of Interfacial Electronic and Energetic Properties of LaAlO 3/TiO 2 and TiO 2/LaAlO 3 Heterostructures from First-Principles Calculations. ACS APPLIED MATERIALS & INTERFACES 2017; 9:7682-7690. [PMID: 28139115 DOI: 10.1021/acsami.6b12254] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
By using first-principles electronic structure calculations, we studied electronic and energetic properties of perovskite oxide heterostructures with different epitaxial growth order between anatase TiO2 and LaAlO3. Two types of heterostructures, i.e., TiO2 film grown on LaAlO3 substrate (TiO2/LaAlO3) and LaAlO3 film grown on TiO2 substrate (LaAlO3/TiO2), were modeled. The TiO2/LaAlO3 model is intrinsically metallic and thus does not exhibit an insulator-to-metal transition as TiO2 film thickness increases; in contrast, the LaAlO3/TiO2 model shows an insulator-to-metal transition as the LaAlO3 film thickness increases up to 4 unit cells. The former model has a larger interfacial charge carrier density (n ∼ 1014 cm-2) and smaller electron effective mass (0.47me) than the later one (n ∼ 1013 cm-2, and 0.70me). The interfacial energetics calculations indicate that the TiO2/LaAlO3 model is energetically more favorable than the LaAlO3/TiO2 model, and the former has a stronger interface cohesion than the later model. This research provides fundamental insights into the different interfacial electronic and energetic properties of TiO2/LaAlO3 and LaAlO3/TiO2 heterostructures.
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Affiliation(s)
- Jianli Cheng
- Department of NanoEngineering, University of California, San Diego , 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States
| | - Jian Luo
- Department of NanoEngineering, University of California, San Diego , 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States
| | - Kesong Yang
- Department of NanoEngineering, University of California, San Diego , 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States
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39
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Lee M, Arras R, Warot-Fonrose B, Hungria T, Lippmaa M, Daimon H, Casanove MJ. Strain induced atomic structure at the Ir-doped LaAlO3/SrTiO3 interface. Phys Chem Chem Phys 2017; 19:28676-28683. [DOI: 10.1039/c7cp05918c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Different levels of Ir doping at the LaAlO3/SrTiO3 interface affect the strain state in LaAlO3, as investigated using atomically resolved microscopy (HAADF-STEM), electron energy loss spectroscopy (EELS) and first-principles calculations (DFT).
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Affiliation(s)
- M. Lee
- Centre d’Elaboration des Matériaux et d’Etudes Structurales (CEMES)
- CNRS UPR 8011 and Université de Toulouse
- F-31055 Toulouse
- France
- Nara Institute of Science and Technology (NAIST)
| | - R. Arras
- Centre d’Elaboration des Matériaux et d’Etudes Structurales (CEMES)
- CNRS UPR 8011 and Université de Toulouse
- F-31055 Toulouse
- France
| | - B. Warot-Fonrose
- Centre d’Elaboration des Matériaux et d’Etudes Structurales (CEMES)
- CNRS UPR 8011 and Université de Toulouse
- F-31055 Toulouse
- France
| | - T. Hungria
- Centre de MicroCaractérisation Raimond Castaing
- Université de Toulouse
- F-31400 Toulouse
- France
| | - M. Lippmaa
- Institute for Solid State Physics
- University of Tokyo
- 277-8581 Chiba
- Japan
| | - H. Daimon
- Nara Institute of Science and Technology (NAIST)
- Ikoma 630-0192
- Japan
| | - M. J. Casanove
- Centre d’Elaboration des Matériaux et d’Etudes Structurales (CEMES)
- CNRS UPR 8011 and Université de Toulouse
- F-31055 Toulouse
- France
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40
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Guo H, Saidi WA, Zhao J. Tunability of the two-dimensional electron gas at the LaAlO 3/SrTiO 3 interface by strain-induced ferroelectricity. Phys Chem Chem Phys 2016; 18:28474-28484. [PMID: 27711681 DOI: 10.1039/c6cp04769f] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The two-dimensional electron gas (2DEG) formed at the interface between two insulating materials LaAlO3 (LAO) and SrTiO3 (STO) has recently generated a lot of interest. Here, based on first-principles density functional theory calculations, we investigate the existence and stability of the 2DEG under the application of a biaxial strain on the LAO/STO(001) heterostructure. The compressive strain induces ferroelectric (FE) polarization in STO, which allows for the tunability of the 2DEG by reversing the STO polarization orientation. We show that the formation of the 2DEG is unstable when LAO and STO have the same polarization direction. On the other hand, the 2DEG will always form if the two polarizations are in the opposite directions regardless of the LAO thickness, which is in contrast to the unstrained interface that has a critical thickness for stabilizing the 2DEG. We show that the underpinnings of this behavior are due to charge passivation and band gap alignment.
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Affiliation(s)
- Hongli Guo
- ICQD/Hefei National Laboratory for Physical Sciences at Microscale, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China. and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Wissam A Saidi
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
| | - Jin Zhao
- ICQD/Hefei National Laboratory for Physical Sciences at Microscale, and Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China. and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China and Department of Physics, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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41
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Yang K, Nazir S, Behtash M, Cheng J. High-Throughput Design of Two-Dimensional Electron Gas Systems Based on Polar/Nonpolar Perovskite Oxide Heterostructures. Sci Rep 2016; 6:34667. [PMID: 27708415 PMCID: PMC5052574 DOI: 10.1038/srep34667] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 09/19/2016] [Indexed: 11/15/2022] Open
Abstract
The two-dimensional electron gas (2DEG) formed at the interface between two insulating oxides such as LaAlO3 and SrTiO3 (STO) is of fundamental and practical interest because of its novel interfacial conductivity and its promising applications in next-generation nanoelectronic devices. Here we show that a group of combinatorial descriptors that characterize the polar character, lattice mismatch, band gap, and the band alignment between the perovskite-oxide-based band insulators and the STO substrate, can be introduced to realize a high-throughput (HT) design of SrTiO3-based 2DEG systems from perovskite oxide quantum database. Equipped with these combinatorial descriptors, we have carried out a HT screening of all the polar perovskite compounds, uncovering 42 compounds of potential interests. Of these, Al-, Ga-, Sc-, and Ta-based compounds can form a 2DEG with STO, while In-based compounds exhibit a strain-induced strong polarization when deposited on STO substrate. In particular, the Ta-based compounds can form 2DEG with potentially high electron mobility at (TaO2)+/(SrO)0 interface. Our approach, by defining materials descriptors solely based on the bulk materials properties, and by relying on the perovskite-oriented quantum materials repository, opens new avenues for the discovery of perovskite-oxide-based functional interface materials in a HT fashion.
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Affiliation(s)
- Kesong Yang
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, USA
| | - Safdar Nazir
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, USA
| | - Maziar Behtash
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, USA
| | - Jianli Cheng
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, USA
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42
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Lee PW, Singh VN, Guo GY, Liu HJ, Lin JC, Chu YH, Chen CH, Chu MW. Hidden lattice instabilities as origin of the conductive interface between insulating LaAlO3 and SrTiO3. Nat Commun 2016; 7:12773. [PMID: 27624682 PMCID: PMC5027288 DOI: 10.1038/ncomms12773] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 08/01/2016] [Indexed: 11/09/2022] Open
Abstract
The metallic interface between insulating LaAlO3 and SrTiO3 opens up the field of oxide electronics. With more than a decade of researches on this heterostructure, the origin of the interfacial conductivity, however, remains unsettled. Here we resolve this long-standing puzzle by atomic-scale observation of electron-gas formation for screening hidden lattice instabilities, rejuvenated near the interface by epitaxial strain. Using atomic-resolution imaging and electron spectroscopy, the generally accepted notions of polar catastrophe and cation intermixing for the metallic interface are discounted. Instead, the conductivity onset at the critical thickness of 4-unit cell LaAlO3 on SrTiO3 substrate is accompanied with head-to-head ferroelectric-like polarizations across the interface due to strain-rejuvenated ferroelectric-like instabilities in the materials. The divergent depolarization fields of the head-to-head polarizations cast the interface into an electron reservoir, forming screening electron gas in SrTiO3 with LaAlO3 hosting complementary localized holes. The ferroelectric-like polarizations and electron–hole juxtaposition reveal the cooperative nature of metallic LaAlO3/SrTiO3. The origin of interfacial conductivity between two insulating oxides, LaAlO3 and SrTiO3, remains elusive despite a long time research. Here, Lee et al. report atomic-scale observation of electron-gas formation for screening hidden ferroelectric-like lattice instabilities, discounting the role of polar catastrophe and cation intermixing.
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Affiliation(s)
- P W Lee
- Department of Physics, National Taiwan University, Taipei 106, Taiwan.,Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan
| | - V N Singh
- Department of Physics, National Taiwan University, Taipei 106, Taiwan.,Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan
| | - G Y Guo
- Department of Physics, National Taiwan University, Taipei 106, Taiwan.,Physics Division, National Center for Theoretical Sciences, Hsinchu 300, Taiwan
| | - H-J Liu
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
| | - J-C Lin
- Institute of Physics, Academia Sinica, Taipei 105, Taiwan
| | - Y-H Chu
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan.,Institute of Physics, Academia Sinica, Taipei 105, Taiwan
| | - C H Chen
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan.,Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
| | - M-W Chu
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan
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43
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Tomczyk M, Cheng G, Lee H, Lu S, Annadi A, Veazey JP, Huang M, Irvin P, Ryu S, Eom CB, Levy J. Micrometer-Scale Ballistic Transport of Electron Pairs in LaAlO_{3}/SrTiO_{3} Nanowires. PHYSICAL REVIEW LETTERS 2016; 117:096801. [PMID: 27610871 DOI: 10.1103/physrevlett.117.096801] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Indexed: 06/06/2023]
Abstract
High-mobility complex-oxide heterostructures and nanostructures offer new opportunities for extending the paradigm of quantum transport beyond the realm of traditional III-V or carbon-based materials. Recent quantum transport investigations with LaAlO_{3}/SrTiO_{3}-based quantum dots reveal the existence of a strongly correlated phase in which electrons form spin-singlet pairs without becoming superconducting. Here, we report evidence for the micrometer-scale ballistic transport of electron pairs in quasi-1D LaAlO_{3}/SrTiO_{3} nanowire cavities. In the paired phase, Fabry-Perot-like quantum interference is observed, in sync with conductance oscillations observed in the superconducting regime (at a zero magnetic field). Above a critical magnetic field B_{p}, the electron pairs unbind and the conductance oscillations shift with the magnetic field. These experimental observations extend the regime of ballistic electronic transport to strongly correlated phases.
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Affiliation(s)
- Michelle Tomczyk
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Guanglei Cheng
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Shicheng Lu
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Anil Annadi
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Joshua P Veazey
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - Mengchen Huang
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Sangwoo Ryu
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
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44
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Hong S, Nakhmanson SM, Fong DD. Screening mechanisms at polar oxide heterointerfaces. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:076501. [PMID: 27308889 DOI: 10.1088/0034-4885/79/7/076501] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The interfaces of polar oxide heterostructures can display electronic properties unique from the oxides they border, as they require screening from either internal or external sources of charge. The screening mechanism depends on a variety of factors, including the band structure at the interface, the presence of point defects or adsorbates, whether or not the oxide is ferroelectric, and whether or not an external field is applied. In this review, we discuss both theoretical and experimental aspects of different screening mechanisms, giving special emphasis to ways in which the mechanism can be altered to provide novel or tunable functionalities. We begin with a theoretical introduction to the problem and highlight recent progress in understanding the impact of point defects on polar interfaces. Different case studies are then discussed, for both the high thickness regime, where interfaces must be screened and each interface can be considered separately, and the low thickness regime, where the degree and nature of screening can be manipulated and the interfaces are close enough to interact. We end with a brief outlook toward new developments in this rapidly progressing field.
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Affiliation(s)
- Seungbum Hong
- Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA. Department of Materials Science & Engineering, KAIST, Daejeon 305-701, Korea
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45
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Atomic-resolved depth profile of strain and cation intermixing around LaAlO3/SrTiO3 interfaces. Sci Rep 2016; 6:28118. [PMID: 27301609 PMCID: PMC4908387 DOI: 10.1038/srep28118] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 05/27/2016] [Indexed: 11/09/2022] Open
Abstract
Novel behavior has been observed at the interface of LaAlO3/SrTiO3 heterostructures such as two dimensional metallic conductivity, magnetic scattering and superconductivity. However, both the origins and quantification of such behavior have been complicated due to an interplay of mechanical, chemical and electronic factors. Here chemical and strain profiles near the interface of LaAlO3/SrTiO3 heterostructures are correlated. Conductive and insulating samples have been processed, with thicknesses respectively above and below the commonly admitted conductivity threshold. The intermixing and structural distortions within the crystal lattice have been quantitatively measured near the interface with a depth resolution of unit cell size. A strong link between intermixing and structural distortions at such interfaces is highlighted: intermixing was more pronounced in the hetero-couple with conductive interface, whereas in-plane compressive strains extended deeper within the substrate of the hetero-couple with the insulating interface. This allows a better understanding of the interface local mechanisms leading to the conductivity.
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46
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Domain topology and domain switching kinetics in a hybrid improper ferroelectric. Nat Commun 2016; 7:11602. [PMID: 27215944 PMCID: PMC4890185 DOI: 10.1038/ncomms11602] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 04/12/2016] [Indexed: 11/08/2022] Open
Abstract
Charged polar interfaces such as charged ferroelectric walls or heterostructured interfaces of ZnO/(Zn,Mg)O and LaAlO3/SrTiO3, across which the normal component of electric polarization changes suddenly, can host large two-dimensional conduction. Charged ferroelectric walls, which are energetically unfavourable in general, were found to be mysteriously abundant in hybrid improper ferroelectric (Ca,Sr)3Ti2O7 crystals. From the exploration of antiphase boundaries in bilayer-perovskites, here we discover that each of four polarization-direction states is degenerate with two antiphase domains, and these eight structural variants form a Z4 × Z2 domain structure with Z3 vortices and five distinct types of domain walls, whose topology is directly relevant to the presence of abundant charged walls. We also discover a zipper-like nature of antiphase boundaries, which are the reversible creation/annihilation centres of pairs of two types of ferroelectric walls (and also Z3-vortex pairs) in 90° and 180° polarization switching. Our results demonstrate the unexpectedly rich nature of hybrid improper ferroelectricity.
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47
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Han K, Palina N, Zeng SW, Huang Z, Li CJ, Zhou WX, Wan DY, Zhang LC, Chi X, Guo R, Chen JS, Venkatesan T, Rusydi A, Ariando A. Controlling Kondo-like Scattering at the SrTiO3-based Interfaces. Sci Rep 2016; 6:25455. [PMID: 27147407 PMCID: PMC4857089 DOI: 10.1038/srep25455] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 04/13/2016] [Indexed: 11/08/2022] Open
Abstract
The observation of magnetic interaction at the interface between nonmagnetic oxides has attracted much attention in recent years. In this report, we show that the Kondo-like scattering at the SrTiO3-based conducting interface is enhanced by increasing the lattice mismatch and growth oxygen pressure PO2. For the 26-unit-cell LaAlO3/SrTiO3 (LAO/STO) interface with lattice mismatch being 3.0%, the Kondo-like scattering is observed when PO2 is beyond 1 mTorr. By contrast, when the lattice mismatch is reduced to 1.0% at the (La0.3Sr0.7)(Al0.65Ta0.35)O3/SrTiO3 (LSAT/STO) interface, the metallic state is always preserved up to PO2 of 100 mTorr. The data from Hall measurement and X-ray absorption near edge structure (XANES) spectroscopy reveal that the larger amount of localized Ti(3+) ions are formed at the LAO/STO interface compared to LSAT/STO. Those localized Ti(3+) ions with unpaired electrons can be spin-polarized to scatter mobile electrons, responsible for the Kondo-like scattering observed at the LAO/STO interface.
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Affiliation(s)
- K. Han
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - N. Palina
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Singapore Synchrotron Light Source, National University of Singapore, Singapore 117603, Singapore
| | - S. W. Zeng
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Z. Huang
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
| | - C. J. Li
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
| | - W. X. Zhou
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - D.-Y. Wan
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - L. C. Zhang
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - X. Chi
- Singapore Synchrotron Light Source, National University of Singapore, Singapore 117603, Singapore
| | - R. Guo
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Material Science & Engineering, National University of Singapore, Singapore 117575, Singapore
| | - J. S. Chen
- Department of Material Science & Engineering, National University of Singapore, Singapore 117575, Singapore
| | - T. Venkatesan
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- Department of Material Science & Engineering, National University of Singapore, Singapore 117575, Singapore
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Singapore
- National University of Singapore Graduate School for Integrative Sciences and Engineering (NGS), 28 Medical Drive, Singapore 117456, Singapore
| | - A. Rusydi
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- Singapore Synchrotron Light Source, National University of Singapore, Singapore 117603, Singapore
| | - A Ariando
- NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
- Department of Physics, National University of Singapore, Singapore 117542, Singapore
- National University of Singapore Graduate School for Integrative Sciences and Engineering (NGS), 28 Medical Drive, Singapore 117456, Singapore
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48
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Dai W, Adhikari S, Garcia-Castro AC, Romero AH, Lee H, Lee JW, Ryu S, Eom CB, Cen C. Tailoring LaAlO3/SrTiO3 Interface Metallicity by Oxygen Surface Adsorbates. NANO LETTERS 2016; 16:2739-2743. [PMID: 26928809 DOI: 10.1021/acs.nanolett.6b00421] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report an oxygen surface adsorbates induced metal-insulator transition at the LaAlO3/SrTiO3 interfaces. The observed effects were attributed to the terminations of surface Al sites and the resultant electron-accepting surface states. By controlling the local oxygen adsorptions, we successfully demonstrated the nondestructive patterning of the interface two-dimensional electron gas (2DEG). The obtained 2DEG structures are stable in air and also robust against general solvent treatments. This study provides new insights into the metal-insulator transition mechanism at the complex oxide interfaces and also a highly efficient technique for tailoring the interface properties.
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Affiliation(s)
- Weitao Dai
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
| | - Sanjay Adhikari
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
| | - Andrés Camilo Garcia-Castro
- Physique Théorique des Matériaux, Université de Liège , B-4000 Sart-Tilman, Belgium
- Centro de Investigación y Estudios Avanzados del IPN , MX-76230 Querétaro, México
| | - Aldo H Romero
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
| | - Hyungwoo Lee
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Jung-Woo Lee
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Sangwoo Ryu
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Chang-Beom Eom
- Department of Material Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Cheng Cen
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506, United States
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49
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Moon SY, Moon CW, Chang HJ, Kim T, Kang CY, Choi HJ, Kim JS, Baek SH, Jang HW. Thermal stability of 2DEG at amorphous LaAlO 3/crystalline SrTiO 3 heterointerfaces. NANO CONVERGENCE 2016; 3:7. [PMID: 28191417 PMCID: PMC5271142 DOI: 10.1186/s40580-016-0067-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 02/10/2016] [Indexed: 06/06/2023]
Abstract
At present, the generation of heterostructures with two dimensional electron gas (2DEG) in amorphous LaAlO3 (a-LAO)/SrTiO3 (STO) has been achieved. Herein, we analysed thermal stability of 2DEG at a-LAO/STO interfaces in comparison with 2DEG at crystalline LaAlO3 (c-LAO)/STO interfaces. To create 2DEG at LAO/STO interface, regardless of growing temperature from 25 to 700 °C, we found that environment with oxygen deficient during the deposition of LAO overlayer is essentially required. That indicates that the oxygen-poor condition in the system is more essential than the crystalline nature of LAO layer. 2DEG at a-LAO/STO interface is depleted upon ex situ annealing at 300 °C under 300 Torr of oxygen pressure, while that in c-LAO/STO interface is still maintained. Our result suggests that the LAO overlayer crystallinity critically affects the thermal-annealing-induced depletion of 2DEG at a-LAO/STO interface rather than the generation of 2DEG. We clearly provide that amorphous TiOx can efficiently prevent the thermal degradation of 2DEG at the a-LAO/STO interface, which gives a cornerstone for achieving thermal-stable 2DEG at a-LAO/STO interface.
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Affiliation(s)
- Seon Young Moon
- Center for Electronic Materials, Korea Institute of Science and Technology, Seoul, 136-791 Republic of Korea
- Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749 Republic of Korea
| | - Cheon Woo Moon
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul, 151-744 Republic of Korea
| | - Hye Jung Chang
- Center for Electronic Materials, Korea Institute of Science and Technology, Seoul, 136-791 Republic of Korea
- Department of Nanomaterials Science and Technology, Korea University of Science and Technology, Daejeon, 305-350 Republic of Korea
| | - Taemin Kim
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul, 151-744 Republic of Korea
| | - Chong-Yun Kang
- Center for Electronic Materials, Korea Institute of Science and Technology, Seoul, 136-791 Republic of Korea
- Department of Nanomaterials Science and Technology, Korea University of Science and Technology, Daejeon, 305-350 Republic of Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 136-701 Republic of Korea
| | - Heon-Jin Choi
- Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749 Republic of Korea
| | - Jin-Sang Kim
- Center for Electronic Materials, Korea Institute of Science and Technology, Seoul, 136-791 Republic of Korea
| | - Seung-Hyub Baek
- Center for Electronic Materials, Korea Institute of Science and Technology, Seoul, 136-791 Republic of Korea
- Department of Nanomaterials Science and Technology, Korea University of Science and Technology, Daejeon, 305-350 Republic of Korea
| | - Ho Won Jang
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul, 151-744 Republic of Korea
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50
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Brown KA, He S, Eichelsdoerfer DJ, Huang M, Levy I, Lee H, Ryu S, Irvin P, Mendez-Arroyo J, Eom CB, Mirkin CA, Levy J. Giant conductivity switching of LaAlO3/SrTiO3 heterointerfaces governed by surface protonation. Nat Commun 2016; 7:10681. [PMID: 26861842 PMCID: PMC4749969 DOI: 10.1038/ncomms10681] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 01/11/2016] [Indexed: 11/09/2022] Open
Abstract
Complex-oxide interfaces host a diversity of phenomena not present in traditional semiconductor heterostructures. Despite intense interest, many basic questions remain about the mechanisms that give rise to interfacial conductivity and the role of surface chemistry in dictating these properties. Here we demonstrate a fully reversible >4 order of magnitude conductance change at LaAlO3/SrTiO3 (LAO/STO) interfaces, regulated by LAO surface protonation. Nominally conductive interfaces are rendered insulating by solvent immersion, which deprotonates the hydroxylated LAO surface; interface conductivity is restored by exposure to light, which induces reprotonation via photocatalytic oxidation of adsorbed water. The proposed mechanisms are supported by a coordinated series of electrical measurements, optical/solvent exposures, and X-ray photoelectron spectroscopy. This intimate connection between LAO surface chemistry and LAO/STO interface physics bears far-reaching implications for reconfigurable oxide nanoelectronics and raises the possibility of novel applications in which electronic properties of these materials can be locally tuned using synthetic chemistry.
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Affiliation(s)
- Keith A Brown
- Department of Chemistry and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208, USA
| | - Shu He
- Department of Chemistry and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208, USA
| | - Daniel J Eichelsdoerfer
- Department of Chemistry and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208, USA
| | - Mengchen Huang
- Department of Physics and Astronomy, University of Pittsburgh, 100 Allen Hall, 3941 O'Hara Street, Pittsburgh, Pennsylvania 15260, USA.,Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Ishan Levy
- Department of Physics and Astronomy, University of Pittsburgh, 100 Allen Hall, 3941 O'Hara Street, Pittsburgh, Pennsylvania 15260, USA.,Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Sangwoo Ryu
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Patrick Irvin
- Department of Physics and Astronomy, University of Pittsburgh, 100 Allen Hall, 3941 O'Hara Street, Pittsburgh, Pennsylvania 15260, USA.,Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
| | - Jose Mendez-Arroyo
- Department of Chemistry and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208, USA
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Chad A Mirkin
- Department of Chemistry and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208, USA
| | - Jeremy Levy
- Department of Physics and Astronomy, University of Pittsburgh, 100 Allen Hall, 3941 O'Hara Street, Pittsburgh, Pennsylvania 15260, USA.,Pittsburgh Quantum Institute, Pittsburgh, Pennsylvania 15260, USA
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