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Nian L, Li J, Wang Z, Zhang T, Sun H, Li Y, Gao T, Deng Y, Nie Y, Hao Y. Synthesis of Oxide Interface-Based Two-Dimensional Electron Gas on Si. ACS APPLIED MATERIALS & INTERFACES 2022; 14:53442-53449. [PMID: 36383755 DOI: 10.1021/acsami.2c18934] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Two-dimensional electron gas (2DEG) at the interface of amorphous Al2O3/SrTiO3 (aAO/STO) heterostructures has received considerable attention owing to its convenience of fabrication and relatively high mobility. The integration of these 2DEG heterostructures on a silicon wafer is highly desired for electronic applications but remains challanging up to date. Here, conductive aAO/STO heterostructures have been synthesized on a silicon wafer via a growth-and-transfer method. A scanning transmission electron microscopy image shows flat and close contact between STO membranes and a Si wafer. Electron energy loss spectroscopic measurements reveal the interfacial Ti valence state evolution, which identifies the formation of 2D charge carriers confined at the interface of aAO/STO. This work provides a feasible strategy for the integration of 2DEG on a silicon wafer and other desired substrates for potential functional and flexible electronic devices.
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Affiliation(s)
- Leyan Nian
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing, Jiangsu 210023, People's Republic of China
| | - Jiayi Li
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing, Jiangsu 210023, People's Republic of China
| | - Zhichao Wang
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing, Jiangsu 210023, People's Republic of China
| | - Tingting Zhang
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing, Jiangsu 210023, People's Republic of China
| | - Haoying Sun
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing, Jiangsu 210023, People's Republic of China
| | - Yueying Li
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing, Jiangsu 210023, People's Republic of China
| | - Tianyi Gao
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing, Jiangsu 210023, People's Republic of China
| | - Yu Deng
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing, Jiangsu 210023, People's Republic of China
| | - Yuefeng Nie
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing, Jiangsu 210023, People's Republic of China
| | - Yufeng Hao
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing, Jiangsu 210023, People's Republic of China
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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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Chikina A, Christensen DV, Borisov V, Husanu MA, Chen Y, Wang X, Schmitt T, Radovic M, Nagaosa N, Mishchenko AS, Valentí R, Pryds N, Strocov VN. Band-Order Anomaly at the γ-Al 2O 3/SrTiO 3 Interface Drives the Electron-Mobility Boost. ACS NANO 2021; 15:4347-4356. [PMID: 33661601 DOI: 10.1021/acsnano.0c07609] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The rich functionalities of transition-metal oxides and their interfaces bear an enormous technological potential. Its realization in practical devices requires, however, a significant improvement of yet relatively low electron mobility in oxide materials. Recently, a mobility boost of about 2 orders of magnitude has been demonstrated at the spinel-perovskite γ-Al2O3/SrTiO3 interface compared to the paradigm perovskite-perovskite LaAlO3/SrTiO3 interface. We explore the fundamental physics behind this phenomenon from direct measurements of the momentum-resolved electronic structure of this interface using resonant soft-X-ray angle-resolved photoemission. We find an anomaly in orbital ordering of the mobile electrons in γ-Al2O3/SrTiO3 which depopulates electron states in the top SrTiO3 layer. This rearrangement of the mobile electron system pushes the electron density away from the interface, which reduces its overlap with the interfacial defects and weakens the electron-phonon interaction, both effects contributing to the mobility boost. A crystal-field analysis shows that the band order alters owing to the symmetry breaking between the spinel γ-Al2O3 and perovskite SrTiO3. Band-order engineering, exploiting the fundamental symmetry properties, emerges as another route to boost the performance of oxide devices.
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Affiliation(s)
- Alla Chikina
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
- Institute of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus, Denmark
| | - Dennis V Christensen
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Vladislav Borisov
- Institut für Theoretische Physik, Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
- Department of Physics and Astronomy, Uppsala University, Box 516, 5120 Uppsala, Sweden
| | - Marius-Adrian Husanu
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
- National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania
| | - Yunzhong Chen
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiaoqiang Wang
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - Thorsten Schmitt
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
| | - Naoto Nagaosa
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
- Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Andrey S Mishchenko
- RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
| | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Vladimir N Strocov
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
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Spectral weight reduction of two-dimensional electron gases at oxide surfaces across the ferroelectric transition. Sci Rep 2020; 10:16834. [PMID: 33033329 PMCID: PMC7545169 DOI: 10.1038/s41598-020-73657-1] [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: 05/22/2020] [Accepted: 09/02/2020] [Indexed: 11/11/2022] Open
Abstract
The discovery of a two-dimensional electron gas (2DEG) at the \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {LaAlO}_3/\hbox {SrTiO}_3$$\end{document}LaAlO3/SrTiO3 interface has set a new platform for all-oxide electronics which could potentially exhibit the interplay among charge, spin, orbital, superconductivity, ferromagnetism and ferroelectricity. In this work, by using angle-resolved photoemission spectroscopy and conductivity measurement, we found the reduction of 2DEGs and the changes of the conductivity nature of some ferroelectric oxides including insulating Nb-lightly-substituted \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {KTaO}_3$$\end{document}KTaO3, \documentclass[12pt]{minimal}
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\begin{document}$$\hbox {BaTiO}_3$$\end{document}BaTiO3 (BTO) and (Ca,Zr)-doped BTO across paraelectric-ferroelectric transition. We propose that these behaviours could be due to the increase of space-charge screening potential at the 2DEG/ferroelectric regions which is a result of the realignment of ferroelectric polarisation upon light irradiation. This finding suggests an opportunity for controlling the 2DEG at a bare oxide surface (instead of interfacial system) by using both light and ferroelectricity.
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Liu M, Hong Y, Xue H, Meng J, Jiang W, Zhang Z, Ling J, Dou R, Xiong C, He L, Nie J. Enhancement of Rashba spin-orbit coupling by electron confinement at the LaAlO 3/SrTiO 3 interface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:235003. [PMID: 32050164 DOI: 10.1088/1361-648x/ab7579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Electrical transport property is closely related to the dimensionality of carriers' distribution. In this work, we succeed in tuning the carriers' distribution and the Rashba spin-orbit coupling at LaAlO3/SrTiO3 interface by varying the oxygen pressure (c-P O2) adopted in crystalline LaAlO3 growth. Measurements of the in-plane anisotropic magnetoresistance and the conducting-layer thickness indicate that the carriers' distribution changes from three to two dimensions with c-P O2 increasing, i.e. the electron confinement gets stronger. Importantly, by measuring the low-temperature out-of-plane magnetoresistance and analyzing the weak localization/weak anti-localization, we find that the strength of Rashba spin-orbit coupling can be enhanced by electron confinement. The electron confinement is a manifestation of breaking of spatial inversion symmetry. Therefore, our work reveals the intimate relationship between spatial inversion symmetry breaking and Rashba spin-orbit coupling at the LaAlO3/SrTiO3 interface, and provides a new method to tune the Rashba spin-orbit coupling, which is valuable in the application of oxide-spintronics.
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Affiliation(s)
- Mingrui Liu
- Department of Physics, Beijing Normal University, Beijing 100875, People's Republic of China
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Ladewig C, Anwar F, Lee V, Kelber JA, Shah SQA, Dowben PA. Ultrathin Chromia on a Hexagonally-Ordered d 0 Ferromagnet: Evidence of Interfacial Exchange Bias at the Cr 2O 3/TiO 2-x Interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:14797-14803. [PMID: 31661625 DOI: 10.1021/acs.langmuir.9b02654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Heterostructures consisting of 10 Å thick chromia films and 50 Å thick titania films display significant exchange bias at and above room temperature. Chromia films ∼10 Å thick were deposited by molecular beam epitaxy (MBE) of Cr at room temperature in ultrahigh vacuum on 50 Å thick TiO2-x(111) films (x < 0.3) also deposited epitaxially by MBE on Al2O3(0001). Cr deposition yields increased Ti(III) formation in the titania substrate and the formation of a Cr2O3 overlayer, without Cr/Ti interfacial mixing, as determined by in situ photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS). In situ low-energy electron diffraction (LEED) and XPS data indicate that the chromia overlayer is hexagonally ordered and ∼10 Å thick. Longitudinal and polar magneto-optic Kerr effect (MOKE) measurements at 285-315 K provide evidence of strong exchange bias between the boundary layer magnetization of chromia and the ferromagnetic substrate. These data demonstrate the robust room-temperature interaction of the boundary layer magnetization of a multiferroic antiferromagnet with a d0 ferromagnetic substrate.
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Affiliation(s)
- Chad Ladewig
- Department of Chemistry , University of North Texas , Denton , Texas 76203 , United States
| | - Fatima Anwar
- Department of Chemistry , University of North Texas , Denton , Texas 76203 , United States
| | - Veronica Lee
- Department of Chemistry , University of North Texas , Denton , Texas 76203 , United States
| | - Jeffry A Kelber
- Department of Chemistry , University of North Texas , Denton , Texas 76203 , United States
| | - Syed Q A Shah
- Department of Physics and Astronomy , University of Nebraska-Lincoln , Lincoln , Nebraska 68588 , United States
| | - Peter A Dowben
- Department of Physics and Astronomy , University of Nebraska-Lincoln , Lincoln , Nebraska 68588 , United States
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Puebla J, Auvray F, Yamaguchi N, Xu M, Bisri SZ, Iwasa Y, Ishii F, Otani Y. Photoinduced Rashba Spin-to-Charge Conversion via an Interfacial Unoccupied State. PHYSICAL REVIEW LETTERS 2019; 122:256401. [PMID: 31347901 DOI: 10.1103/physrevlett.122.256401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 04/03/2019] [Indexed: 06/10/2023]
Abstract
At interfaces with inversion symmetry breaking, the Rashba effect couples the motion of the electrons to their spin; as a result, a spin charge interconversion mechanism can occur. These interconversion mechanisms commonly exploit Rashba spin splitting at the Fermi level by spin pumping or spin torque ferromagnetic resonance. Here, we report evidence of significant photoinduced spin-to-charge conversion via Rashba spin splitting in an unoccupied state above the Fermi level at the Cu(111)/α-Bi_{2}O_{3} interface. We predict an average Rashba coefficient of 1.72×10^{-10} eV m at 1.98 eV above the Fermi level, by a fully relativistic first principles analysis of the interfacial electronic structure with spin orbit interaction. We find agreement with our observation of helicity dependent photoinduced spin-to-charge conversion excited at 1.96 eV at room temperature, with a spin current generation of J_{s}=10^{6} A/m^{2}. The present Letter shows evidence of efficient spin charge conversion exploiting Rashba spin splitting at excited states, harvesting light energy without magnetic materials or external magnetic fields.
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Affiliation(s)
| | - Florent Auvray
- Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan
| | - Naoya Yamaguchi
- Division of Mathematical and Physical Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan
| | - Mingran Xu
- Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan
| | | | - Yoshihiro Iwasa
- CEMS, RIKEN, Saitama, 351-0198, Japan
- Quantum Phase Electronic Center (QPEC) and Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Fumiyuki Ishii
- Faculty of Mathematics and Physics, Institute of Science and Engineering, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan
- Nanomaterials Research Institute, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa, 920-1192, Japan
| | - Yoshichika Otani
- CEMS, RIKEN, Saitama, 351-0198, Japan
- Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan
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