1
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Ding C, Dong W, Jiao X, Zhang Z, Gong G, Wei Z, Wang L, Jia JF, Xue QK. Unidirectional Charge Orders Induced by Oxygen Vacancies on SrTiO 3(001). ACS NANO 2024. [PMID: 38935417 DOI: 10.1021/acsnano.4c03317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/28/2024]
Abstract
The discovery of high-mobility two-dimensional electron gas and low carrier density superconductivity in multiple SrTiO3-based heterostructures has stimulated intense interest in the surface properties of SrTiO3. The recent discovery of high-Tc superconductivity in the monolayer FeSe/SrTiO3 led to the upsurge and underscored the atomic precision probe of the surface structure. By performing atomically resolved cryogenic scanning tunneling microscopy/spectroscopy characterization on dual-TiO2-δ-terminated SrTiO3(001) surfaces with (√13 × √13), c(4 × 2), mixed (2 × 1), and (2 × 2) reconstructions, we disclosed universally broken rotational symmetry and contrasting bias- and temperature-dependent electronic states for apical and equatorial oxygen sites. With the sequentially evolved surface reconstructions and simultaneously increasing equatorial oxygen vacancies, the surface anisotropy reduces and the work function lowers. Intriguingly, unidirectional stripe orders appear on the c(4 × 2) surface, whereas local (4 × 4) order emerges and eventually forms long-range unidirectional c(4 × 4) charge order on the (2 × 2) surface. This work reveals robust unidirectional charge orders induced by oxygen vacancies due to strong and delicate electronic-lattice interaction under broken rotational symmetry, providing insights into understanding the complex behaviors in perovskite oxide-based heterostructures.
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Affiliation(s)
- Cui Ding
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Quantum Science Center of Guangdong-HongKong-Macao Greater Bay Area, Shenzhen 518045, China
| | - Wenfeng Dong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Xiaotong Jiao
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Zhiyu Zhang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Guanming Gong
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
| | - Zhongxu Wei
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Lili Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - Jin-Feng Jia
- Quantum Science Center of Guangdong-HongKong-Macao Greater Bay Area, Shenzhen 518045, China
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
- Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China
- Quantum Science Center of Guangdong-HongKong-Macao Greater Bay Area, Shenzhen 518045, China
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
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2
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Li Y, Zhang Y, Shi L, Liu X, Zhang Z, Xie M, Dong Y, Jiang H, Zhu Y, Zhu J. Activating Inert Perovskite Oxides for CO 2 Electroreduction via Slight Cu 2+ Doping in B-Sites. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2402823. [PMID: 38712472 DOI: 10.1002/smll.202402823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Revised: 04/30/2024] [Indexed: 05/08/2024]
Abstract
Perovskite oxides are proven as a striking platform for developing high-performance electrocatalysts. Nonetheless, a significant portion of them show CO2 electroreduction (CO2RR) inertness. Here a simple but effective strategy is reported to activate inert perovskite oxides (e.g., SrTiO3) for CO2RR through slight Cu2+ doping in B-sites. For the proof-of-concept catalysts of SrTi1-xCuxO3 (x = 0.025, 0.05, and 0.1), Cu2+ doping (even in trace amount, e.g., x = 0.025) can not only create active, stable CuO6 octahedra, increase electrochemical active surface area, and accelerate charge transfer, but also significantly regulate the electronic structure (e.g., up-shifted band center) to promote activation/adsorption of reaction intermediates. Benefiting from these merits, the stable SrTi1-xCuxO3 catalysts feature great improvements (at least an order of magnitude) in CO2RR activity and selectivity for high-order products (i.e., CH4 and C2+), compared to the SrTiO3 parent. This work provides a new avenue for the conversion of inert perovskite oxides into high-performance electrocatalysts toward CO2RR.
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Affiliation(s)
- Yuxi Li
- Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, 214122, China
| | - Yu Zhang
- Qingdao New Energy Shandong Laboratory, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China
| | - Lei Shi
- Joint International Research Laboratory of Biomass Energy and Materials, College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, 210037, China
| | - Xiangjian Liu
- Qingdao New Energy Shandong Laboratory, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China
| | - Zhenbao Zhang
- School of Chemistry and Chemical Engineering, Linyi University, Linyi, 276005, China
| | - Minghao Xie
- Materials Science and Engineering Program and Walker Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Yuming Dong
- Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, 214122, China
| | - Heqing Jiang
- Qingdao New Energy Shandong Laboratory, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China
| | - Yongfa Zhu
- Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Jiawei Zhu
- Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, 214122, China
- Qingdao New Energy Shandong Laboratory, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China
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3
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Düring PM, Rosenberger P, Baumgarten L, Alarab F, Lechermann F, Strocov VN, Müller M. Tunable 2D Electron- and 2D Hole States Observed at Fe/SrTiO 3 Interfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2309217. [PMID: 38245856 DOI: 10.1002/adma.202309217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 10/27/2023] [Indexed: 01/22/2024]
Abstract
Oxide electronics provide the key concepts and materials for enhancing silicon-based semiconductor technologies with novel functionalities. However, a basic but key property of semiconductor devices still needs to be unveiled in its oxidic counterparts: the ability to set or even switch between two types of carriers-either negatively (n) charged electrons or positively (p) charged holes. Here, direct evidence for individually emerging n- or p-type 2D band dispersions in STO-based heterostructures is provided using resonant photoelectron spectroscopy. The key to tuning the carrier character is the oxidation state of an adjacent Fe-based interface layer: For Fe and FeO, hole bands emerge in the empty bandgap region of STO due to hybridization of Ti- and Fe- derived states across the interface, while for Fe3O4 overlayers, an 2D electron system is formed. Unexpected oxygen vacancy characteristics arise for the hole-type interfaces, which as of yet had been exclusively assigned to the emergence of 2DESs. In general, this finding opens up the possibility to straightforwardly switch the type of conductivity at STO interfaces by the oxidation state of a redox overlayer. This will extend the spectrum of phenomena in oxide electronics, including the realization of combined n/p-type all-oxide transistors or logic gates.
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Affiliation(s)
- Pia M Düring
- Fachbereich Physik, Universität Konstanz, 78457, Konstanz, Germany
| | - Paul Rosenberger
- Fachbereich Physik, Universität Konstanz, 78457, Konstanz, Germany
- Fakultät Physik, Technische Universität Dortmund, 44221, Dortmund, Germany
| | - Lutz Baumgarten
- Forschungszentrum Jülich GmbH, Peter Grünberg Institut (PGI-6), 52425, Jülich, Germany
| | - Fatima Alarab
- Paul Scherrer Institute, Swiss Light Source, Villingen PSI, CH-5232, Switzerland
| | - Frank Lechermann
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Vladimir N Strocov
- Paul Scherrer Institute, Swiss Light Source, Villingen PSI, CH-5232, Switzerland
| | - Martina Müller
- Fachbereich Physik, Universität Konstanz, 78457, Konstanz, Germany
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4
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Hunter A, Putzke C, Gaponenko I, Tamai A, Baumberger F, Moll PJW. Controlling crystal cleavage in focused ion beam shaped specimens for surface spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2024; 95:033905. [PMID: 38456757 DOI: 10.1063/5.0186480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 02/13/2024] [Indexed: 03/09/2024]
Abstract
Our understanding of quantum materials is commonly based on precise determinations of their electronic spectrum by spectroscopic means, most notably angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy. Both require atomically clean and flat crystal surfaces, which are traditionally prepared by in situ mechanical cleaving in ultrahigh vacuum chambers. We present a new approach that addresses three main issues of the current state-of-the-art methods: (1) Cleaving is a highly stochastic and, thus, inefficient process; (2) fracture processes are governed by the bonds in a bulk crystal, and many materials and surfaces simply do not cleave; and (3) the location of the cleave is random, preventing data collection at specified regions of interest. Our new workflow is based on focused ion beam machining of micro-strain lenses, in which shape (rather than crystalline) anisotropy dictates the plane of cleavage, which can be placed at a specific target layer. As proof-of-principle, we show ARPES results from micro-cleaves of Sr2RuO4 along the ac plane and from two surface orientations of SrTiO3, a notoriously difficult to cleave cubic perovskite.
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Affiliation(s)
- A Hunter
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - C Putzke
- Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany
- Laboratory of Quantum Materials (QMAT), Institute of Materials (IMX), École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - I Gaponenko
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - A Tamai
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - F Baumberger
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - P J W Moll
- Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany
- Laboratory of Quantum Materials (QMAT), Institute of Materials (IMX), École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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5
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Caputo M, Studniarek M, Guedes EB, Schio L, Baiseitov K, Daffé N, Bachellier N, Chikina A, Di Santo G, Verdini A, Goldoni A, Muntwiler M, Piamonteze C, Floreano L, Radovic M, Dreiser J. Charge Transfer and Orbital Reconstruction at an Organic-Oxide Interface. NANO LETTERS 2023. [PMID: 38029285 DOI: 10.1021/acs.nanolett.3c03713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
The two-dimensional electron system (2DES) located at the surface of strontium titanate (STO) and at several other STO-based interfaces has been an established platform for the study of novel physical phenomena since its discovery. Here we report how the interfacing of STO and tetracyanoquinodimethane (TCNQ) results in a charge transfer that depletes the number of free carriers at the STO surface, with a strong impact on its electronic structure. Our study paves the way for efficient tuning of the electronic properties, which promises novel applications in the framework of oxide/organic-based electronics.
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Affiliation(s)
- Marco Caputo
- Elettra Sincrotrone Trieste, s.s. 14 km 163.5 in Area Science Park, 34149 Trieste, Italy
- MAX IV Laboratory, Lund University, PO Box 118, 22100 Lund, Sweden
| | - Michał Studniarek
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Eduardo Bonini Guedes
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Luca Schio
- Laboratorio TASC, Istituto Officina dei Materiali (IOM)-CNR, Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Kassymkhan Baiseitov
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Niéli Daffé
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Nicolas Bachellier
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Alla Chikina
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Giovanni Di Santo
- Elettra Sincrotrone Trieste, s.s. 14 km 163.5 in Area Science Park, 34149 Trieste, Italy
| | - Alberto Verdini
- Laboratorio TASC, Istituto Officina dei Materiali (IOM)-CNR, Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Andrea Goldoni
- Elettra Sincrotrone Trieste, s.s. 14 km 163.5 in Area Science Park, 34149 Trieste, Italy
| | - Matthias Muntwiler
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Cinthia Piamonteze
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Luca Floreano
- Laboratorio TASC, Istituto Officina dei Materiali (IOM)-CNR, Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Jan Dreiser
- Swiss Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
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6
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Luo D, Chen Y, Wang Y, Cao X, Aung P, Jin K, Wang S. Electrical transport behavior of the oxygen vacancies-rich LaAlO 3/SrTiO 3heterogeneous interface at high temperature. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 36:095001. [PMID: 37972407 DOI: 10.1088/1361-648x/ad0d29] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Accepted: 11/16/2023] [Indexed: 11/19/2023]
Abstract
Oxygen vacancy is one of the original mechanisms of the two-dimensional electron gas (2DEG) at the LaAlO3(LAO) and SrTiO3(STO) heterogeneous interface, and it has an important impact on the electrical properties of LAO/STO heterojunction. In this work, the LAO thin films were grown on the STO substrates by pulsed laser deposition, and the electrical transport behavior of the LAO/STO interface at high temperature and high vacuum were systematically studied. It was found that at high temperature and high vacuum, the oxygen vacancies-rich LAO/STO heterojunction would undergo a metal-insulator transition, and return to metal conductivity when the temperature is further increased. At this time, the conduction mechanism of the sample is drift mode and the thermal activation energy is 0.87 eV. While during the temperature decreasing, the conduction mechanism would transfer to hopping conduction with the thermal activation energy of 0.014 eV and the resistance would increase dramatically and present a completely insulated state. However, when the oxygen vacancies-rich sample is exposed to air, the resistance would gradually decrease and recover.
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Affiliation(s)
- Dianbing Luo
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions, School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
| | - Yunhai Chen
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions, School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
| | - Yifei Wang
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions, School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
| | - Xinyu Cao
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions, School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
| | - Phyo Aung
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions, School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
| | - Kexin Jin
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions, School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
| | - Shuanhu Wang
- Shaanxi Key Laboratory of Condensed Matter Structures and Properties and MOE Key Laboratory of Materials Physics and Chemistry under Extraordinary Conditions, School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
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7
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Fung V, Hu G, Wu Z, Jiang DE. Hydrogen-mediated polarity compensation on the (110) surface terminations of ABO3 perovskites. J Chem Phys 2023; 159:174706. [PMID: 37929866 DOI: 10.1063/5.0161435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2023] [Accepted: 10/17/2023] [Indexed: 11/07/2023] Open
Abstract
Polar surfaces undergo polarity compensation, which can lead to significantly different surface chemistry from their nonpolar counterparts. This process in turn can substantially alter the binding of adsorbates on the surface. Here, we find that hydrogen binds much more strongly to the polar (110) surface than the nonpolar (100) surface for a wide range of ABO3 perovskites, forming a hydroxyl layer on the O24- termination and a hydride layer on the ABO4+ termination of the (110) surface. The stronger adsorption on the polar surfaces can be explained by polarity compensation: hydrogen atoms can act as electron donors or acceptors to compensate for the polarity of perovskite surfaces. The relative stability of the surface terminations is further compared under different gas environments and several perovskites have been found to form stable surface hydride layers under oxygen-poor conditions. These results demonstrate the feasibility of creating stable surface hydrides on perovskites by polarity compensation which might lead to new hydrogenation catalysts based on ABO3 perovskites.
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Affiliation(s)
- Victor Fung
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Guoxiang Hu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Zili Wu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - De-En Jiang
- Department of Chemistry, University of California, Riverside, California 92521, USA
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235, USA
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8
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Yang G, Kim Y, Jeon J, Lee M, Kim D, Kim S, Eom K, Lee H. Reversible Photomodulation of Two-Dimensional Electron Gas in LaAlO 3/SrTiO 3 Heterostructures. NANO LETTERS 2023. [PMID: 37418557 DOI: 10.1021/acs.nanolett.3c01076] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/09/2023]
Abstract
Long-lived photoinduced conductance changes in LaAlO3/SrTiO3 (LAO/STO) heterostructures enable their use in optoelectronic memory applications. However, it remains challenging to quench the persistent photoconductivity (PPC) instantly and reproducibly, which limits the reversible optoelectronic switching. Herein, we demonstrate a reversible photomodulation of two-dimensional electron gas (2DEG) in LAO/STO heterostructures with high reproducibility. By irradiating UV pulses, the 2DEG at the LAO/STO interface is gradually transformed to the PPC state. Notably, the PPC can be completely removed by water treatment when two key requirements are met: (1) the moderate oxygen deficiency in STO and (2) the minimal band edge fluctuation at the interface. Through our X-ray photoelectron spectroscopy and electrical noise analysis, we reveal that the reproducible change in the conductivity of 2DEG is directly attributed to the surface-driven electron relaxation in the STO. Our results provide a stepping-stone toward developing optically tunable memristive devices based on oxide 2DEG systems.
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Affiliation(s)
- Gyeongmo Yang
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Youngmin Kim
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Jaeyoung Jeon
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Minkyung Lee
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Doyeop Kim
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
| | - Sungkyu Kim
- Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 05006, Republic of Korea
| | - Kitae Eom
- School of Advanced Materials science and Engineering, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Hyungwoo Lee
- Department of Energy Systems Research, Ajou University, Suwon 16499, Republic of Korea
- Department of Physics, Ajou University, Suwon 16499, Republic of Korea
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9
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Rubano A, Paparo D. Optical Second Harmonic Generation on LaAlO 3/SrTiO 3 Interfaces: A Review. MATERIALS (BASEL, SWITZERLAND) 2023; 16:4337. [PMID: 37374522 DOI: 10.3390/ma16124337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 05/30/2023] [Accepted: 05/31/2023] [Indexed: 06/29/2023]
Abstract
As we approach the limits of semiconductor technology, the development of new materials and technologies for the new era in electronics is compelling. Among others, perovskite oxide hetero-structures are anticipated to be the best candidates. As in the case of semiconductors, the interface between two given materials can have, and often has, very different properties, compared to the corresponding bulk compounds. Perovskite oxides show spectacular interfacial properties due to the the rearrangement of charges, spins, orbitals and the lattice structure itself, at the interface. Lanthanum aluminate and Strontium titanate hetero-structures (LaAlO3/SrTiO3) can be regarded as a prototype of this wider class of interfaces. Both bulk compounds are plain and (relatively) simple wide-bandgap insulators. Despite this, a conductive two-dimensional electron gas (2DEG) is formed right at the interface when a LaAlO3 thickness of n≥4 unit cells is deposited on a SrTiO3 substrate. The 2DEG is quite thin, being confined in only one or at least very few mono-layers at the interface, on the SrTiO3 side. A very intense and long-lasting study was triggered by this surprising discovery. Many questions regarding the origin and characteristics of the two-dimensional electron gas have been (partially) addressed, others are still open. In particular, this includes the interfacial electronic band structure, the transverse plane spatial homogeneity of the samples and the ultrafast dynamics of the confined carriers. Among a very long list of experimental techniques which have been exploited to study these types of interfaces (ARPES, XPS, AFM, PFM, …and many others), optical Second Harmonic Generation (SHG) was found to be suitable for investigating these types of buried interfaces, thanks to its extreme and selective interface-only sensitivity. The SHG technique has made its contribution to the research in this field in a variety of different and important aspects. In this work we will give a bird's eye view of the currently available research on this topic and try to sketch out its future perspectives.
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Affiliation(s)
- Andrea Rubano
- Physics Department "E. Pancini", University Federico II, Monte S. Angelo, Via Cintia, 80126 Naples, Italy
- Institute of Applied Sciences and Intelligent Systems (ISASI), Consiglio Nazionale delle Ricerche (CNR), Via Campi Flegrei 34, 80078 Pozzuoli, Italy
| | - Domenico Paparo
- Institute of Applied Sciences and Intelligent Systems (ISASI), Consiglio Nazionale delle Ricerche (CNR), Via Campi Flegrei 34, 80078 Pozzuoli, Italy
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10
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Scott JI, Adams RL, Martinez-Gazoni RF, Carroll LR, Downard AJ, Veal TD, Reeves RJ, Allen MW. Looking Outside the Square: The Growth, Structure, and Resilient Two-Dimensional Surface Electron Gas of Square SnO 2 Nanotubes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023:e2300520. [PMID: 37191281 DOI: 10.1002/smll.202300520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 03/31/2023] [Indexed: 05/17/2023]
Abstract
Nanotechnology has delivered an amazing range of new materials such as nanowires, tubes, ribbons, belts, cages, flowers, and sheets. However, these are usually circular, cylindrical, or hexagonal in nature, while nanostructures with square geometries are comparatively rare. Here, a highly scalable method is reported for producing vertically aligned Sb-doped SnO2 nanotubes with perfectly-square geometries on Au nanoparticle covered m-plane sapphire using mist chemical vapor deposition. Their inclination can be varied using r- and a-plane sapphire, while unaligned square nanotubes of the same high structural quality can be grown on silicon and quartz. X-ray diffraction measurements and transmission electron microscopy show that they adopt the rutile structure growing in the [001] direction with (110) sidewalls, while synchrotron X-ray photoelectron spectroscopy reveals the presence of an unusually strong and thermally resilient 2D surface electron gas. This is created by donor-like states produced by the hydroxylation of the surface and is sustained at temperatures above 400 °C by the formation of in-plane oxygen vacancies. This persistent high surface electron density is expected to prove useful in gas sensing and catalytic applications of these remarkable structures. To illustrate their device potential, square SnO2 nanotube Schottky diodes and field effect transistors with excellent performance characteristics are fabricated.
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Affiliation(s)
- Jonty I Scott
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Ryan L Adams
- Department of Electrical and Computer Engineering and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Rodrigo F Martinez-Gazoni
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Liam R Carroll
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Alison J Downard
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Tim D Veal
- Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool, Liverpool, L69 7ZF, UK
| | - Roger J Reeves
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Martin W Allen
- Department of Electrical and Computer Engineering and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
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11
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Bhattacharya S, Datta S. Evidence of linear and cubic Rashba effect in non-magnetic heterostructure. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 35:205501. [PMID: 36848680 DOI: 10.1088/1361-648x/acbf94] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 02/27/2023] [Indexed: 06/18/2023]
Abstract
TheLaAlO3/KTaO3system serves as a prototype to study the electronic properties that emerge as a result of spin-orbit coupling (SOC). In this article, we have used first-principles calculations to systematically study two types of defect-free (0 0 1) interfaces, which are termed as Type-I and Type-II. While the Type-I heterostructure produces a two dimensional (2D) electron gas, the Type-II heterostructure hosts an oxygen-rich 2D hole gas at the interface. Furthermore, in the presence of intrinsic SOC, we have found evidence of both cubic and linear Rashba interactions in the conduction bands of the Type-I heterostructure. On the contrary, there is spin-splitting of both the valence and the conduction bands in the Type-II interface, which are found to be only linear Rashba type. Interestingly, the Type-II interface also harbors a potential photocurrent transition path, making it an excellent platform to study the circularly polarized photogalvanic effect.
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Affiliation(s)
- Sanchari Bhattacharya
- Department of Physics and Astronomy, National Institute of Technology, Rourkela, 769008 Odisha, India
| | - Sanjoy Datta
- Department of Physics and Astronomy, National Institute of Technology, Rourkela, 769008 Odisha, India
- Center for Nanomaterials, National Institute of Technology, Rourkela, 769008 Odisha, India
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12
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Tunable superconductivity and its origin at KTaO 3 interfaces. Nat Commun 2023; 14:951. [PMID: 36806127 PMCID: PMC9941122 DOI: 10.1038/s41467-023-36309-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 01/23/2023] [Indexed: 02/22/2023] Open
Abstract
What causes Cooper pairs to form in unconventional superconductors is often elusive because experimental signatures that connect to a specific pairing mechanism are rare. Here, we observe distinct dependences of the superconducting transition temperature Tc on carrier density n2D for electron gases formed at KTaO3 (111), (001) and (110) interfaces. For the (111) interface, a remarkable linear dependence of Tc on n2D is observed over a range of nearly one order of magnitude. Further, our study of the dependence of superconductivity on gate electric fields reveals the role of the interface in mediating superconductivity. We find that the extreme sensitivity of superconductivity to crystallographic orientation can be explained by pairing via inter-orbital interactions induced by an inversion-breaking transverse optical phonon and quantum confinement. This mechanism is also consistent with the dependence of Tc on n2D. Our study may shed light on the pairing mechanism in other superconducting quantum paraelectrics.
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13
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Kim S, Bang J, Lim CY, Lee SY, Hyun J, Lee G, Lee Y, Denlinger JD, Huh S, Kim C, Song SY, Seo J, Thapa D, Kim SG, Lee YH, Kim Y, Kim SW. Quantum electron liquid and its possible phase transition. NATURE MATERIALS 2022; 21:1269-1274. [PMID: 36175520 DOI: 10.1038/s41563-022-01353-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 08/04/2022] [Indexed: 06/16/2023]
Abstract
Purely quantum electron systems exhibit intriguing correlated electronic phases by virtue of quantum fluctuations in addition to electron-electron interactions. To realize such quantum electron systems, a key ingredient is dense electrons decoupled from other degrees of freedom. Here, we report the discovery of a pure quantum electron liquid that spreads up to ~3 Å in a vacuum on the surface of an electride crystal. Its extremely high electron density and weak hybridization with buried atomic orbitals show the quantum and pure nature of the electrons, which exhibit a polarized liquid phase, as demonstrated by our spin-dependent measurement. Furthermore, upon enhancing the electron correlation strength, the dynamics of the quantum electrons change to that of a non-Fermi liquid along with an anomalous band deformation, suggestive of a transition to a hexatic liquid crystal phase. Our findings develop the frontier of quantum electron systems and serve as a platform for exploring correlated electronic phases in a pure fashion.
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Affiliation(s)
- Sunghun Kim
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Joonho Bang
- Department of Energy Science, Sungkyunkwan University, Suwon, Korea
| | - Chan-Young Lim
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Seung Yong Lee
- Department of Energy Science, Sungkyunkwan University, Suwon, Korea
| | - Jounghoon Hyun
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Gyubin Lee
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Yeonghoon Lee
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | | | - Soonsang Huh
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, Korea
| | - Changyoung Kim
- Center for Correlated Electron Systems, Institute for Basic Science, Seoul, Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, Korea
| | - Sang Yong Song
- Department of Emerging Materials Science, DGIST, Daegu, Korea
| | - Jungpil Seo
- Department of Emerging Materials Science, DGIST, Daegu, Korea
| | - Dinesh Thapa
- Department of Physics & Astronomy and Center for Computational Sciences, Mississippi State University, Mississippi State, MS, USA
| | - Seong-Gon Kim
- Department of Physics & Astronomy and Center for Computational Sciences, Mississippi State University, Mississippi State, MS, USA
| | - Young Hee Lee
- Department of Energy Science, Sungkyunkwan University, Suwon, Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon, Korea
| | - Yeongkwan Kim
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, Korea.
| | - Sung Wng Kim
- Department of Energy Science, Sungkyunkwan University, Suwon, Korea.
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon, Korea.
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14
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Noh S, Choe D, Jin H, Yoo JW. Enhancement of the Rashba Effect in a Conducting SrTiO 3 Surface by MoO 3 Capping. ACS APPLIED MATERIALS & INTERFACES 2022; 14:50280-50287. [PMID: 36282511 DOI: 10.1021/acsami.2c11840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Systems having inherent structural asymmetry retain the Rashba-type spin-orbit interaction, which ties the spin and momentum of electrons in the band structure, leading to coupled spin and charge transport. One of the electrical manifestations of the Rashba spin-orbit interaction is nonreciprocal charge transport, which could be utilized for rectifying devices. Further tuning of the Rashba spin-orbit interaction allows additional functionalities in spin-orbitronic applications. In this work, we present our study of nonreciprocal charge transport in a conducting SrTiO3 (001) surface and its significant enhancement by a capping layer. The conductive strontium titanate SrTiO3 (STO) (001) surface was created through oxygen vacancies by Ar+ irradiation, and the nonreciprocal signal was probed by angle- and magnetic field-dependent second harmonic voltage measurement with an AC current. We observed robust directional transport in the Ar+-irradiated sample at low temperatures. The magnitude of the nonreciprocal signal is highly dependent on the irradiation time as it affects the depth of the conducting layer and the impact of the topmost conducting layer. Moreover, the nonreciprocal resistance was significantly enhanced by simply adding a MoO3 capping layer on the conductive STO surface. These results show a simple methodology for tuning and investigating the Rashba effect in a conductive STO surface, which could be adopted for various two-dimensional (2D) conducting layers for spin-orbitronic applications.
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Affiliation(s)
- Seunghyeon Noh
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan44919, Korea
| | - Daeseong Choe
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan44919, Korea
| | - Hosub Jin
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan44919, Korea
| | - Jung-Woo Yoo
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan44919, Korea
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15
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Kaneta-Takada S, Kitamura M, Arai S, Arai T, Okano R, Anh LD, Endo T, Horiba K, Kumigashira H, Kobayashi M, Seki M, Tabata H, Tanaka M, Ohya S. Giant spin-to-charge conversion at an all-epitaxial single-crystal-oxide Rashba interface with a strongly correlated metal interlayer. Nat Commun 2022; 13:5631. [PMID: 36163469 PMCID: PMC9512910 DOI: 10.1038/s41467-022-33350-5] [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: 01/06/2022] [Accepted: 09/12/2022] [Indexed: 11/30/2022] Open
Abstract
The two-dimensional electron gas (2DEG) formed at interfaces between SrTiO3 (STO) and other oxide insulating layers is promising for use in efficient spin-charge conversion due to the large Rashba spin-orbit interaction (RSOI). However, these insulating layers on STO prevent the propagation of a spin current injected from an adjacent ferromagnetic layer. Moreover, the mechanism of the spin-current flow in these insulating layers is still unexplored. Here, using a strongly correlated polar-metal LaTiO3+δ (LTO) interlayer and the 2DEG formed at the LTO/STO interface in an all-epitaxial heterostructure, we demonstrate giant spin-to-charge current conversion efficiencies, up to ~190 nm, using spin-pumping ferromagnetic-resonance voltage measurements. This value is the highest among those reported for all materials, including spin Hall systems. Our results suggest that the strong on-site Coulomb repulsion in LTO and the giant RSOI of LTO/STO may be the key to efficient spin-charge conversion with suppressed spin-flip scattering. Our findings highlight the hidden inherent possibilities of oxide interfaces for spin-orbitronics applications. The interface between perovskite-oxide SrTiO3 and other oxides realizes efficient spin-to-charge current conversion; however, the typically insulating oxides hinder the propagation of spin-currents. Here the authors achieve a record efficiency by replacing an oxide insulator with a strongly-correlated polar metal.
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Affiliation(s)
- Shingo Kaneta-Takada
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Miho Kitamura
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan
| | - Shoma Arai
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Takuma Arai
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Ryo Okano
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Le Duc Anh
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.,PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
| | - Tatsuro Endo
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Koji Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan.,Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai, Miyagi, 980-8577, Japan
| | - Masaki Kobayashi
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.,Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Munetoshi Seki
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.,Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Hitoshi Tabata
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.,Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Masaaki Tanaka
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan. .,Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Shinobu Ohya
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan. .,Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
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16
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Wang Y, Gao Q, Li W, Cheng P, Zhang YQ, Feng B, Hu Z, Wu K, Chen L. Nearly Ideal Two-Dimensional Electron Gas Hosted by Multiple Quantized Kronig-Penney States Observed in Few-Layer InSe. ACS NANO 2022; 16:13014-13021. [PMID: 35943244 DOI: 10.1021/acsnano.2c05556] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
A theoretical ideal two-dimensional electron gas (2DEG) was characterized by a flat density of states independent of energy. Compared with conventional two-dimensional free-electron systems in semiconductor heterojunctions and noble metal surfaces, we report here the achievement of ideal 2DEG with multiple quantized states in few-layer InSe films. The multiple quantum well states (QWSs) in few-layer InSe films are found, and the number of QWSs is strictly equal to the number of atomic layers. The multiple stair-like DOS as well as multiple bands with parabolic dispersion both characterize ideal 2DEG features in these QWSs. Density functional theory calculations and numerical simulations based on quasi-bounded square potential wells described as the Kronig-Penney model provide a consistent explanation of 2DEG in the QWSs. Our work demonstrates that 2D van der Waals materials are ideal systems for realizing 2DEG hosted by multiple quantized Kronig-Penney states, and the semiconducting nature of the material provides a better chance for construction of high-performance electronic devices utilizing these states, for example, superlattice devices with negative differential resistance.
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Affiliation(s)
- Yu Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Qian Gao
- School of Physics, Nankai University, Tianjin 300071, China
| | - Wenhui Li
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Peng Cheng
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Yi-Qi Zhang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Baojie Feng
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Zhenpeng Hu
- School of Physics, Nankai University, Tianjin 300071, China
| | - Kehui Wu
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Lan Chen
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
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17
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Wang Z, Reticcioli M, Jakub Z, Sokolović I, Meier M, Boatner LA, Schmid M, Parkinson GS, Diebold U, Franchini C, Setvin M. Surface chemistry on a polarizable surface: Coupling of CO with KTaO 3(001). SCIENCE ADVANCES 2022; 8:eabq1433. [PMID: 35984882 PMCID: PMC9390988 DOI: 10.1126/sciadv.abq1433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 07/06/2022] [Indexed: 06/15/2023]
Abstract
Polarizable materials attract attention in catalysis because they have a free parameter for tuning chemical reactivity. Their surfaces entangle the dielectric polarization with surface polarity, excess charge, and orbital hybridization. How this affects individual adsorbed molecules is shown for the incipient ferroelectric perovskite KTaO3. This intrinsically polar material cleaves along (001) into KO- and TaO2-terminated surface domains. At TaO2 terraces, the polarity-compensating excess electrons form a two-dimensional electron gas and can also localize by coupling to ferroelectric distortions. TaO2 terraces host two distinct types of CO molecules, adsorbed at equivalent lattice sites but charged differently as seen in atomic force microscopy/scanning tunneling microscopy. Temperature-programmed desorption shows substantially stronger binding of the charged CO; in density functional theory calculations, the excess charge favors a bipolaronic configuration coupled to the CO. These results pinpoint how adsorption states couple to ferroelectric polarization.
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Affiliation(s)
- Zhichang Wang
- Institute of Applied Physics, TU Wien, Vienna, Austria
- State Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China
| | - Michele Reticcioli
- Faculty of Physics and Center for Computational Materials Science, University of Vienna, Vienna, Austria
| | - Zdenek Jakub
- Institute of Applied Physics, TU Wien, Vienna, Austria
| | | | | | - Lynn A. Boatner
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | | | | | | | - Cesare Franchini
- Faculty of Physics and Center for Computational Materials Science, University of Vienna, Vienna, Austria
- Dipartimento di Fisica e Astronomia, Universita di Bologna, 40127 Bologna, Italy
| | - Martin Setvin
- Institute of Applied Physics, TU Wien, Vienna, Austria
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, 180 00 Prague 8, Czech Republic
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18
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Bellini V, Rusponi S, Kolorenč J, Mahatha SK, Valbuena MA, Persichetti L, Pivetta M, Sorokin BV, Merk D, Reynaud S, Sblendorio D, Stepanow S, Nistor C, Gargiani P, Betto D, Mugarza A, Gambardella P, Brune H, Carbone C, Barla A. Slow Magnetic Relaxation of Dy Adatoms with In-Plane Magnetic Anisotropy on a Two-Dimensional Electron Gas. ACS NANO 2022; 16:11182-11193. [PMID: 35770912 PMCID: PMC9330770 DOI: 10.1021/acsnano.2c04048] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We report on the magnetic properties of Dy atoms adsorbed on the (001) surface of SrTiO3. X-ray magnetic circular dichroism reveals slow relaxation of the Dy magnetization on a time scale of about 800 s at 2.5 K, unusually associated with an easy-plane magnetic anisotropy. We attribute these properties to Dy atoms occupying hollow adsorption sites on the TiO2-terminated surface. Conversely, Ho atoms adsorbed on the same surface show paramagnetic behavior down to 2.5 K. With the help of atomic multiplet simulations and first-principles calculations, we establish that Dy populates also the top-O and bridge sites on the coexisting SrO-terminated surface. A simple magnetization relaxation model predicts these two sites to have an even longer magnetization lifetime than the hollow site. Moreover, the adsorption of Dy on the insulating SrTiO3 crystal leads, regardless of the surface termination, to the formation of a spin-polarized two-dimensional electron gas of Ti 3dxy character, together with an antiferromagnetic Dy-Ti coupling. Our findings support the feasibility of tuning the magnetic properties of the rare-earth atoms by acting on the substrate electronic gas with electric fields.
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Affiliation(s)
- Valerio Bellini
- S3-Istituto
di Nanoscienze-CNR, Via
Campi 213/A, I-41125 Modena, Italy
| | - Stefano Rusponi
- Institute
of Physics, Ecole Polytechnique Fédérale de Lausanne
(EPFL), Station 3, CH-1015 Lausanne, Switzerland
| | - Jindřich Kolorenč
- Institute
of Physics (FZU), Czech Academy of Sciences, Na Slovance 2, CZ-182
21 Prague, Czech Republic
| | - Sanjoy K. Mahatha
- Istituto
di Struttura della Materia (ISM), Consiglio Nazionale delle Ricerche
(CNR), I-34149 Trieste, Italy
- School
of
Physics and Materials Science, Thapar Institute
of Engineering and Technology, Patiala 147004, India
| | - Miguel Angel Valbuena
- Catalan
Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST,
Campus UAB, Bellaterra, E-08193 Barcelona, Spain
- Instituto
Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanoscience), E-28049 Madrid, Spain
| | - Luca Persichetti
- Department
of Materials, ETH Zurich, CH-8093 Zurich, Switzerland
- Dipartimento
di Fisica, Università di Roma “Tor
Vergata”, I-00133 Roma, Italy
| | - Marina Pivetta
- Institute
of Physics, Ecole Polytechnique Fédérale de Lausanne
(EPFL), Station 3, CH-1015 Lausanne, Switzerland
| | - Boris V. Sorokin
- Institute
of Physics, Ecole Polytechnique Fédérale de Lausanne
(EPFL), Station 3, CH-1015 Lausanne, Switzerland
| | - Darius Merk
- Institute
of Physics, Ecole Polytechnique Fédérale de Lausanne
(EPFL), Station 3, CH-1015 Lausanne, Switzerland
| | - Sébastien Reynaud
- Institute
of Physics, Ecole Polytechnique Fédérale de Lausanne
(EPFL), Station 3, CH-1015 Lausanne, Switzerland
| | - Dante Sblendorio
- Institute
of Physics, Ecole Polytechnique Fédérale de Lausanne
(EPFL), Station 3, CH-1015 Lausanne, Switzerland
| | | | - Corneliu Nistor
- Department
of Materials, ETH Zurich, CH-8093 Zurich, Switzerland
| | | | - Davide Betto
- European
Synchrotron Radiation Facility, F-38043 Grenoble Cedex, France
| | - Aitor Mugarza
- Catalan
Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST,
Campus UAB, Bellaterra, E-08193 Barcelona, Spain
- Institució
Catalana de Recerca i Estudis Avançats (ICREA), Barcelona E-08010, Spain
| | | | - Harald Brune
- Institute
of Physics, Ecole Polytechnique Fédérale de Lausanne
(EPFL), Station 3, CH-1015 Lausanne, Switzerland
| | - Carlo Carbone
- Istituto
di Struttura della Materia (ISM), Consiglio Nazionale delle Ricerche
(CNR), I-34149 Trieste, Italy
| | - Alessandro Barla
- Istituto
di Struttura della Materia (ISM), Consiglio Nazionale delle Ricerche
(CNR), I-34149 Trieste, Italy
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19
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Reticcioli M, Wang Z, Schmid M, Wrana D, Boatner LA, Diebold U, Setvin M, Franchini C. Competing electronic states emerging on polar surfaces. Nat Commun 2022; 13:4311. [PMID: 35879300 PMCID: PMC9314351 DOI: 10.1038/s41467-022-31953-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 07/07/2022] [Indexed: 11/28/2022] Open
Abstract
Excess charge on polar surfaces of ionic compounds is commonly described by the two-dimensional electron gas (2DEG) model, a homogeneous distribution of charge, spatially-confined in a few atomic layers. Here, by combining scanning probe microscopy with density functional theory calculations, we show that excess charge on the polar TaO2 termination of KTaO3(001) forms more complex electronic states with different degrees of spatial and electronic localization: charge density waves (CDW) coexist with strongly-localized electron polarons and bipolarons. These surface electronic reconstructions, originating from the combined action of electron-lattice interaction and electronic correlation, are energetically more favorable than the 2DEG solution. They exhibit distinct spectroscopy signals and impact on the surface properties, as manifested by a local suppression of ferroelectric distortions.
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Affiliation(s)
- Michele Reticcioli
- University of Vienna, Faculty of Physics, Center for Computational Materials Science, Vienna, Austria
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
| | - Zhichang Wang
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
- State Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China
| | - Michael Schmid
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
| | - Dominik Wrana
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, 180 00, Prague 8, Czech Republic
| | - Lynn A Boatner
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Ulrike Diebold
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria
| | - Martin Setvin
- Institute of Applied Physics, Technische Universität Wien, Vienna, Austria.
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, 180 00, Prague 8, Czech Republic.
| | - Cesare Franchini
- University of Vienna, Faculty of Physics, Center for Computational Materials Science, Vienna, Austria.
- Dipartimento di Fisica e Astronomia, Università di Bologna, 40127, Bologna, Italy.
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20
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Pesquera D, Fernández A, Khestanova E, Martin LW. Freestanding complex-oxide membranes. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:383001. [PMID: 35779514 DOI: 10.1088/1361-648x/ac7dd5] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 07/01/2022] [Indexed: 06/15/2023]
Abstract
Complex oxides show a vast range of functional responses, unparalleled within the inorganic solids realm, making them promising materials for applications as varied as next-generation field-effect transistors, spintronic devices, electro-optic modulators, pyroelectric detectors, or oxygen reduction catalysts. Their stability in ambient conditions, chemical versatility, and large susceptibility to minute structural and electronic modifications make them ideal subjects of study to discover emergent phenomena and to generate novel functionalities for next-generation devices. Recent advances in the synthesis of single-crystal, freestanding complex oxide membranes provide an unprecedented opportunity to study these materials in a nearly-ideal system (e.g. free of mechanical/thermal interaction with substrates) as well as expanding the range of tools for tweaking their order parameters (i.e. (anti-)ferromagnetic, (anti-)ferroelectric, ferroelastic), and increasing the possibility of achieving novel heterointegration approaches (including interfacing dissimilar materials) by avoiding the chemical, structural, or thermal constraints in synthesis processes. Here, we review the recent developments in the fabrication and characterization of complex-oxide membranes and discuss their potential for unraveling novel physicochemical phenomena at the nanoscale and for further exploiting their functionalities in technologically relevant devices.
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Affiliation(s)
- David Pesquera
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST Campus UAB, Bellaterra, Barcelona 08193, Spain
| | - Abel Fernández
- Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, United States of America
| | | | - Lane W Martin
- Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, United States of America
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States of America
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21
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Yan X, Wrobel F, Tung IC, Zhou H, Hong H, Rodolakis F, Bhattacharya A, McChesney JL, Fong DD. Origin of the 2D Electron Gas at the SrTiO 3 Surface. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2200866. [PMID: 35429184 DOI: 10.1002/adma.202200866] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 04/04/2022] [Indexed: 06/14/2023]
Abstract
Bulk SrTiO3 is a well-known band insulator and the most common substrate used in the field of complex oxide heterostructures. Its surface and interface with other oxides, however, have demonstrated a variety of remarkable behaviors distinct from those expected. In this work, using a suite of in situ techniques to monitor both the atomic and electronic structures of the SrTiO3 (001) surface prior to and during growth, the disappearance and re-appearance of a 2D electron gas (2DEG) is observed after the completion of each SrO and TiO2 monolayer, respectively. The 2DEG is identified with the TiO2 double layer present at the initial SrTiO3 surface, which gives rise to a surface potential and mobile electrons due to vacancies within the TiO2-x adlayer. Much like the electronic reconstruction discovered in other systems, two atomic planes are required, here supplied by the double layer. The combined in situ scattering/spectroscopy findings resolve a number of longstanding issues associated with complex oxide interfaces, facilitating the employment of atomic-scale defect engineering in oxide electronics.
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Affiliation(s)
- Xi Yan
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Friederike Wrobel
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - I-Cheng Tung
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Hua Zhou
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Hawoong Hong
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Fanny Rodolakis
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Anand Bhattacharya
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Jessica L McChesney
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Dillon D Fong
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
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22
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Troglia A, Bigi C, Vobornik I, Fujii J, Knez D, Ciancio R, Dražić G, Fuchs M, Sante DD, Sangiovanni G, Rossi G, Orgiani P, Panaccione G. Evidence of a 2D Electron Gas in a Single-Unit-Cell of Anatase TiO 2 (001). ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2105114. [PMID: 35384406 PMCID: PMC9165519 DOI: 10.1002/advs.202105114] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 01/18/2022] [Indexed: 06/14/2023]
Abstract
The formation and the evolution of electronic metallic states localized at the surface, commonly termed 2D electron gas (2DEG), represents a peculiar phenomenon occurring at the surface and interface of many transition metal oxides (TMO). Among TMO, titanium dioxide (TiO2 ), particularly in its anatase polymorph, stands as a prototypical system for the development of novel applications related to renewable energy, devices and sensors, where understanding the carrier dynamics is of utmost importance. In this study, angle-resolved photo-electron spectroscopy (ARPES) and X-ray absorption spectroscopy (XAS) are used, supported by density functional theory (DFT), to follow the formation and the evolution of the 2DEG in TiO2 thin films. Unlike other TMO systems, it is revealed that, once the anatase fingerprint is present, the 2DEG in TiO2 is robust and stable down to a single-unit-cell, and that the electron filling of the 2DEG increases with thickness and eventually saturates. These results prove that no critical thickness triggers the occurrence of the 2DEG in anatase TiO2 and give insight in formation mechanism of electronic states at the surface of TMO.
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Affiliation(s)
- Alessandro Troglia
- Istituto Officina dei Materiali (IOM)‐CNRLaboratorio TASC in Area Science Park, S.S. 14 Km 163.5Trieste34149Italy
- Dipartimento di FisicaUniversitá di MilanoVia Celoria 16Milano20133Italy
| | - Chiara Bigi
- Istituto Officina dei Materiali (IOM)‐CNRLaboratorio TASC in Area Science Park, S.S. 14 Km 163.5Trieste34149Italy
- Dipartimento di FisicaUniversitá di MilanoVia Celoria 16Milano20133Italy
| | - Ivana Vobornik
- Istituto Officina dei Materiali (IOM)‐CNRLaboratorio TASC in Area Science Park, S.S. 14 Km 163.5Trieste34149Italy
| | - Jun Fujii
- Istituto Officina dei Materiali (IOM)‐CNRLaboratorio TASC in Area Science Park, S.S. 14 Km 163.5Trieste34149Italy
| | - Daniel Knez
- Istituto Officina dei Materiali (IOM)‐CNRLaboratorio TASC in Area Science Park, S.S. 14 Km 163.5Trieste34149Italy
| | - Regina Ciancio
- Istituto Officina dei Materiali (IOM)‐CNRLaboratorio TASC in Area Science Park, S.S. 14 Km 163.5Trieste34149Italy
| | - Goran Dražić
- Department of Materials ChemistryNational Institute of ChemistryHajdrihova 19Ljubljana1001Slovenia
| | - Marius Fuchs
- Institut für Theoretische Physik und Astrophysik and Würzburg‐Dresden Cluster of Excellence ct.qmatUniversität WürzburgWürzburg97074Germany
| | - Domenico Di Sante
- Department of Physics and AstronomyUniversity of BolognaBologna40127Italy
- Center for Computational Quantum PhysicsFlatiron Institute162 5th AvenueNew YorkNY10010USA
| | - Giorgio Sangiovanni
- Institut für Theoretische Physik und Astrophysik and Würzburg‐Dresden Cluster of Excellence ct.qmatUniversität WürzburgWürzburg97074Germany
| | - Giorgio Rossi
- Istituto Officina dei Materiali (IOM)‐CNRLaboratorio TASC in Area Science Park, S.S. 14 Km 163.5Trieste34149Italy
- Dipartimento di FisicaUniversitá di MilanoVia Celoria 16Milano20133Italy
| | - Pasquale Orgiani
- Istituto Officina dei Materiali (IOM)‐CNRLaboratorio TASC in Area Science Park, S.S. 14 Km 163.5Trieste34149Italy
| | - Giancarlo Panaccione
- Istituto Officina dei Materiali (IOM)‐CNRLaboratorio TASC in Area Science Park, S.S. 14 Km 163.5Trieste34149Italy
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23
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Li H, Gan Y, Husanu MA, Dahm RT, Christensen DV, Radovic M, Sun J, Shi M, Shen B, Pryds N, Chen Y. Robust Electronic Structure of Manganite-Buffered Oxide Interfaces with Extreme Mobility Enhancement. ACS NANO 2022; 16:6437-6443. [PMID: 35312282 DOI: 10.1021/acsnano.2c00609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The electronic structure as well as the mechanism underlying the high-mobility two-dimensional electron gases (2DEGs) at complex oxide interfaces remain elusive. Herein, using soft X-ray angle-resolved photoemission spectroscopy (ARPES), we present the band dispersion of metallic states at buffered LaAlO3/SrTiO3 (LAO/STO) heterointerfaces where a single-unit-cell LaMnO3 (LMO) spacer not only enhances the electron mobility but also renders the electronic structure robust toward X-ray radiation. By tracing the evolution of band dispersion, orbital occupation, and electron-phonon interaction of the interfacial 2DEG, we find unambiguous evidence that the insertion of the LMO buffer strongly suppresses both the formation of oxygen vacancies as well as the electron-phonon interaction on the STO side. The latter effect makes the buffered sample different from any other STO-based interfaces and may explain the maximum mobility enhancement achieved at buffered oxide interfaces.
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Affiliation(s)
- Hang Li
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen, PSI, Switzerland
| | - Yulin Gan
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, China
| | - Marius-Adrian Husanu
- National Institute of Materials Physics, Atomistilor 405A, 077125 Magurele, Romania
| | - Rasmus Tindal Dahm
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | | | - Milan Radovic
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen, PSI, Switzerland
| | - Jirong Sun
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, China
| | - Ming Shi
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen, PSI, Switzerland
| | - Baogen Shen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, China
| | - Nini Pryds
- Department of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Yunzhong Chen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, China
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24
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Niu W, Fang YW, Liu R, Wu Z, Chen Y, Gan Y, Zhang X, Zhu C, Wang L, Xu Y, Pu Y, Chen Y, Wang X. Fully Optical Modulation of the Two-Dimensional Electron Gas at the γ-Al 2O 3/SrTiO 3 Interface. J Phys Chem Lett 2022; 13:2976-2985. [PMID: 35343699 DOI: 10.1021/acs.jpclett.2c00384] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Two-dimensional electron gas (2DEG) formed at the heterointerface between two oxide insulators hosts plenty of emergent phenomena and provides new opportunities for electronics and photoelectronics. However, despite being long sought after, on-demand properties controlled through a fully optical illumination remain far from being explored. Herein, a giant tunability of the 2DEG at the interface of γ-Al2O3/SrTiO3 through a fully optical gating is discovered. Specifically, photon-generated carriers lead to a delicate tunability of the carrier density and the underlying electronic structure, which is accompanied by the remarkable Lifshitz transition. Moreover, the 2DEG can be optically tuned to possess a maximum Rashba spin-orbit coupling, particularly at the crossing region of the sub-bands with different symmetries. First-principles calculations essentially well explain the optical modulation of γ-Al2O3/SrTiO3. Our fully optical gating opens a new pathway for manipulating emergent properties of the 2DEGs and is promising for on-demand photoelectric devices.
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Affiliation(s)
- Wei Niu
- New Energy Technology Engineering Laboratory of Jiangsu Province and School of Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Yue-Wen Fang
- Laboratory for Materials and Structures and Tokyo Tech World Research Hub Initiative (WRHI), Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa 226-8503, Japan
- NYU-ECNU Institute of Physics, New York University Shanghai, Shanghai 200122, China
| | - Ruxin Liu
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Zhenqi Wu
- New Energy Technology Engineering Laboratory of Jiangsu Province and School of Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Yongda Chen
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Yulin Gan
- Beijing National Laboratory for Condensed Matter and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiaoqian Zhang
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Chunhui Zhu
- College of Physics, Hebei Normal University, Shijiazhuang 050024, China
| | - Lixia Wang
- New Energy Technology Engineering Laboratory of Jiangsu Province and School of Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Yongbing Xu
- New Energy Technology Engineering Laboratory of Jiangsu Province and School of Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
| | - Yong Pu
- New Energy Technology Engineering Laboratory of Jiangsu Province and School of Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Yunzhong Chen
- Beijing National Laboratory for Condensed Matter and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xuefeng Wang
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China
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25
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Ruano Merchan C, Dorini TT, Brix F, Pasquier L, Jullien M, Pierre D, Andrieu S, Dumesnil K, Parapari SS, Šturm S, Ledieu J, Sicot M, Copie O, Gaudry E, Fournée V. Two-dimensional square and hexagonal oxide quasicrystal approximants in SrTiO 3 films grown on Pt(111)/Al 2O 3(0001). Phys Chem Chem Phys 2022; 24:7253-7263. [PMID: 35275156 DOI: 10.1039/d1cp05296a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The formation of two-dimensional oxide dodecagonal quasicrystals as well as related complex approximant phases was recently reported in thin films derived from BaTiO3 or SrTiO3 perovskites deposited on (111)-oriented Pt single crystals. Here, we use an all-thin-film approach in which the single crystal is replaced by a 10 nm thick Pt(111) buffer layer grown by molecular beam epitaxy on an Al2O3(0001) substrate. An ultra-thin film of SrTiO3 was subsequently deposited by pulsed laser deposition. The film stacking and structure are fully characterized by diffraction and microscopy techniques. We report the discovery of two new complex phases obtained by reduction of this system through high temperature annealing under ultrahigh vacuum conditions. The formation of a new large square approximant with a lattice parameter equal to 44.4 Å is evidenced by low-energy electron diffraction and scanning tunneling microscopy (STM). Additionally, a new 2D hexagonal approximant phase with a lattice parameter of 28 Å has been observed depending on the preparation conditions. Both phases can be described by two different tilings constructed with the same basic square, triangle and rhombus tiles possessing a common edge length of about 6.7 Å. Using the tiling built from high resolution STM images, we propose an atomic model for each approximant which accounts for the experimental observations. Indeed, the STM images simulated using these models are found to be in excellent agreement with the experimental ones, the bright protrusions being attributed to the topmost Sr atoms. In addition our theoretical approach shows that the adhesion of the oxide layer is rather strong (-0.30 eV Å-2). This is attributed to charge transfer, from the most electropositive elements (Sr and Ti) to the most electronegative ones (Pt and O), and to hybridization with Pt-states. Density of states calculations indicate differences in the electronic structure of the two approximants, suggesting different chemical and physical properties. This all-thin-film approach may be useful to explore the formation of complex two-dimensional oxide phases in other metal-oxide combinations.
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Affiliation(s)
- C Ruano Merchan
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France. .,International Associated Laboratory PACS2, CNRS Université de Lorraine, Nancy, France and Jožef Stefan Institute, Ljubljana, Slovenia
| | - T T Dorini
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France. .,International Associated Laboratory PACS2, CNRS Université de Lorraine, Nancy, France and Jožef Stefan Institute, Ljubljana, Slovenia
| | - F Brix
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France. .,International Associated Laboratory PACS2, CNRS Université de Lorraine, Nancy, France and Jožef Stefan Institute, Ljubljana, Slovenia
| | - L Pasquier
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France.
| | - M Jullien
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France.
| | - D Pierre
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France.
| | - S Andrieu
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France.
| | - K Dumesnil
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France.
| | - S S Parapari
- Jožef Stefan Institute, Jamova Cesta 39, Ljubljana 1000, Slovenia.,International Associated Laboratory PACS2, CNRS Université de Lorraine, Nancy, France and Jožef Stefan Institute, Ljubljana, Slovenia
| | - S Šturm
- Jožef Stefan Institute, Jamova Cesta 39, Ljubljana 1000, Slovenia.,International Associated Laboratory PACS2, CNRS Université de Lorraine, Nancy, France and Jožef Stefan Institute, Ljubljana, Slovenia
| | - J Ledieu
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France. .,International Associated Laboratory PACS2, CNRS Université de Lorraine, Nancy, France and Jožef Stefan Institute, Ljubljana, Slovenia
| | - M Sicot
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France. .,International Associated Laboratory PACS2, CNRS Université de Lorraine, Nancy, France and Jožef Stefan Institute, Ljubljana, Slovenia
| | - O Copie
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France.
| | - E Gaudry
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France. .,International Associated Laboratory PACS2, CNRS Université de Lorraine, Nancy, France and Jožef Stefan Institute, Ljubljana, Slovenia
| | - V Fournée
- Institut Jean Lamour UMR 7198, Université de Lorraine - CNRS, Nancy, France. .,International Associated Laboratory PACS2, CNRS Université de Lorraine, Nancy, France and Jožef Stefan Institute, Ljubljana, Slovenia
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26
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Chiu CC, Ho SZ, Lee JM, Shao YC, Shen Y, Liu YC, Chang YW, Zheng YZ, Huang R, Chang CF, Kuo CY, Duan CG, Huang SW, Yang JC, Chuang YD. Presence of Delocalized Ti 3d Electrons in Ultrathin Single-Crystal SrTiO 3. NANO LETTERS 2022; 22:1580-1586. [PMID: 35073104 DOI: 10.1021/acs.nanolett.1c04434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Strontium titanate (STO), with a wide spectrum of emergent properties such as ferroelectricity and superconductivity, has received significant attention in the community of strongly correlated materials. In the strain-free STO film grown on the SrRuO3 buffer layer, the existing polar nanoregions can facilitate room-temperature ferroelectricity when the STO film thickness approaches 10 nm. Here we show that around this thickness scale, the freestanding STO films without the influence of a substrate show the tetragonal structure at room temperature, contrasting with the cubic structure seen in bulk form. The spectroscopic measurements reveal the modified Ti-O orbital hybridization that causes the Ti ion to deviate from its nominal 4+ valency (3d0 configuration) with excess delocalized 3d electrons. Additionally, the Ti ion in TiO6 octahedron exhibits an off-center displacement. The inherent symmetry lowering in ultrathin freestanding films offers an alternative way to achieve tunable electronic structures that are of paramount importance for future technological applications.
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Affiliation(s)
- Chun-Chien Chiu
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Sheng-Zhu Ho
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Jenn-Min Lee
- MAX IV Laboratory, Lund University, P.O. Box 118, 221 00 Lund, Sweden
| | - Yu-Cheng Shao
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Yang Shen
- Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronics, East China Normal University, Shanghai 200241, China
| | - Yu-Chen Liu
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Yao-Wen Chang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
| | - Yun-Zhe Zheng
- Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronics, East China Normal University, Shanghai 200241, China
| | - Rong Huang
- Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronics, East China Normal University, Shanghai 200241, China
| | - Chun-Fu Chang
- Max-Planck Institute for Chemical Physics of Solids, Dresden 01187, Germany
| | - Chang-Yang Kuo
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
- Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan
| | - Chun-Gang Duan
- Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronics, East China Normal University, Shanghai 200241, China
| | - Shih-Wen Huang
- MAX IV Laboratory, Lund University, P.O. Box 118, 221 00 Lund, Sweden
- Swiss Light Source, Paul Scherrer Institut, CH5232 Villigen PSI, Switzerland
| | - Jan-Chi Yang
- Department of Physics, National Cheng Kung University, Tainan 701, Taiwan
- Center for Quantum Frontiers of Research & Technology (QFort), National Cheng Kung University, Tainan 70101, Taiwan
| | - Yi-De Chuang
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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27
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Navas D, Fuentes S, Castro-Alvarez A, Chavez-Angel E. Review on Sol-Gel Synthesis of Perovskite and Oxide Nanomaterials. Gels 2021; 7:275. [PMID: 34940335 PMCID: PMC8700921 DOI: 10.3390/gels7040275] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 12/10/2021] [Accepted: 12/15/2021] [Indexed: 11/16/2022] Open
Abstract
Sol-Gel is a low cost, well-established and flexible synthetic route to produce a wide range of micro- and nanostructures. Small variations in pH, temperature, precursors, time, pressure, atmosphere, among others, can lead to a wide family of compounds that share the same molecular structures. In this work, we present a general review of the synthesis of LaMnO3, SrTiO3, BaTiO3 perovskites and zinc vanadium oxides nanostructures based on Sol-Gel method. We discuss how small changes in the parameters of the synthesis can modify the morphology, shape, size, homogeneity, aggregation, among others, of the products. We also discuss the different precursors, solvents, working temperature, reaction times used throughout the synthesis. In the last section, we present novel uses of Sol-Gel with organic materials with emphasis on carbon-based compounds. All with a perspective to improve the method for future applications in different technological fields.
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Affiliation(s)
- Daniel Navas
- Departamento de Química, Facultad de Ciencias Naturales, Matemática y del Medio Ambiente, Universidad Tecnológica Metropolitana, Las Palmeras 3360, Ñuñoa, Santiago 7800003, Chile;
| | - Sandra Fuentes
- Departamento de Ciencias Farmaceúticas, Facultad de Ciencias, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta 1270709, Chile
- Center for the Development of Nanoscience and Nanotechnology, CEDENNA, Av. Libertador Bernardo O’Higgins 3363, Santiago 9160000, Chile
| | - Alejandro Castro-Alvarez
- Laboratorio de Bioproductos Farmacéuticos y Cosméticos, Centro de Excelencia en Medicina Traslacional, Facultad de Medicina, Universidad de La Frontera, Av. Francisco Salazar 01145, Temuco 4780000, Chile;
| | - Emigdio Chavez-Angel
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
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28
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Resonant tunneling driven metal-insulator transition in double quantum-well structures of strongly correlated oxide. Nat Commun 2021; 12:7070. [PMID: 34862386 PMCID: PMC8642393 DOI: 10.1038/s41467-021-27327-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 11/12/2021] [Indexed: 11/09/2022] Open
Abstract
The metal-insulator transition (MIT), a fascinating phenomenon occurring in some strongly correlated materials, is of central interest in modern condensed-matter physics. Controlling the MIT by external stimuli is a key technological goal for applications in future electronic devices. However, the standard control by means of the field effect, which works extremely well for semiconductor transistors, faces severe difficulties when applied to the MIT. Hence, a radically different approach is needed. Here, we report an MIT induced by resonant tunneling (RT) in double quantum well (QW) structures of strongly correlated oxides. In our structures, two layers of the strongly correlated conductive oxide SrVO3 (SVO) sandwich a barrier layer of the band insulator SrTiO3. The top QW is a marginal Mott-insulating SVO layer, while the bottom QW is a metallic SVO layer. Angle-resolved photoemission spectroscopy experiments reveal that the top QW layer becomes metallized when the thickness of the tunneling barrier layer is reduced. An analysis based on band structure calculations indicates that RT between the quantized states of the double QW induces the MIT. Our work opens avenues for realizing the Mott-transistor based on the wave-function engineering of strongly correlated electrons.
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29
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Shi J, Zhang J, Yang L, Qu M, Qi DC, Zhang KHL. Wide Bandgap Oxide Semiconductors: from Materials Physics to Optoelectronic Devices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2006230. [PMID: 33797084 DOI: 10.1002/adma.202006230] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Revised: 12/30/2020] [Indexed: 06/12/2023]
Abstract
Wide bandgap oxide semiconductors constitute a unique class of materials that combine properties of electrical conductivity and optical transparency. They are being widely used as key materials in optoelectronic device applications, including flat-panel displays, solar cells, OLED, and emerging flexible and transparent electronics. In this article, an up-to-date review on both the fundamental understanding of materials physics of oxide semiconductors, and recent research progress on design of new materials and high-performing thin film transistor (TFT) devices in the context of fundamental understanding is presented. In particular, an in depth overview is first provided on current understanding of the electronic structures, defect and doping chemistry, optical and transport properties of oxide semiconductors, which provide essential guiding principles for new material design and device optimization. With these principles, recent advances in design of p-type oxide semiconductors, new approaches for achieving cost-effective transparent (flexible) electrodes, and the creation of high mobility 2D electron gas (2DEG) at oxide surfaces and interfaces with a wealth of fascinating physical properties of great potential for novel device design are then reviewed. Finally, recent progress and perspective of oxide TFT based on new oxide semiconductors, 2DEG, and low-temperature solution processed oxide semiconductor for flexible electronics will be reviewed.
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Affiliation(s)
- Jueli Shi
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Jiaye Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Lu Yang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Mei Qu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Dong-Chen Qi
- Centre for Materials Science, School of Chemistry and Physics, Queensland University of Technology, Brisbane, Queensland, 4001, Australia
| | - Kelvin H L Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
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30
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Takane D, Kubota Y, Nakayama K, Kawakami T, Yamauchi K, Souma S, Kato T, Sugawara K, Ideta SI, Tanaka K, Kitamura M, Horiba K, Kumigashira H, Oguchi T, Takahashi T, Segawa K, Sato T. Dirac semimetal phase and switching of band inversion in XMg 2Bi 2 (X = Ba and Sr). Sci Rep 2021; 11:21937. [PMID: 34754019 PMCID: PMC8578568 DOI: 10.1038/s41598-021-01333-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 10/26/2021] [Indexed: 11/22/2022] Open
Abstract
Topological Dirac semimetals (TDSs) offer an excellent opportunity to realize outstanding physical properties distinct from those of topological insulators. Since TDSs verified so far have their own problems such as high reactivity in the atmosphere and difficulty in controlling topological phases via chemical substitution, it is highly desirable to find a new material platform of TDSs. By angle-resolved photoemission spectroscopy combined with first-principles band-structure calculations, we show that ternary compound BaMg2Bi2 is a TDS with a simple Dirac-band crossing around the Brillouin-zone center protected by the C3 symmetry of crystal. We also found that isostructural SrMg2Bi2 is an ordinary insulator characterized by the absence of band inversion due to the reduction of spin–orbit coupling. Thus, XMg2Bi2 (X = Sr, Ba, etc.) serves as a useful platform to study the interplay among crystal symmetry, spin–orbit coupling, and topological phase transition around the TDS phase.
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Affiliation(s)
- Daichi Takane
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Yuya Kubota
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Kosuke Nakayama
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan. .,Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Tokyo, 102-0076, Japan.
| | - Tappei Kawakami
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Kunihiko Yamauchi
- Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, 606-8501, Japan
| | - Seigo Souma
- Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan.,Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan
| | - Takemi Kato
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan
| | - Katsuaki Sugawara
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan.,Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Tokyo, 102-0076, Japan.,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan.,Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan
| | - Shin-Ichiro Ideta
- UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki, 444-8585, Japan.,School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, 444-8585, Japan.,Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima, 739-0046, Japan
| | - Kiyohisa Tanaka
- UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki, 444-8585, Japan.,School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, 444-8585, Japan
| | - Miho Kitamura
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, 305-0801, Japan
| | - Koji Horiba
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, 305-0801, Japan.,National Institutes for Quantum and Radiological Science and Technology (QST), Sayo, Hyogo, 679-5148, Japan
| | - Hiroshi Kumigashira
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai, 980-8577, Japan
| | - Tamio Oguchi
- Center for Spintronics Research Network, Osaka University, Toyonaka, 560-8531, Japan.,Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, 567-0047, Japan
| | - Takashi Takahashi
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan.,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan.,Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan
| | - Kouji Segawa
- Department of Physics, Kyoto Sangyo University, Kyoto, 603-8555, Japan
| | - Takafumi Sato
- Department of Physics, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan. .,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan. .,Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai, 980-8577, Japan.
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31
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Zhang J, Pai YY, Lapano J, Mazza AR, Lee HN, Moore RG, Lawrie BJ, Ward TZ, Eres G, Cooper VR, Brahlek M. Design and Realization of Ohmic and Schottky Interfaces for Oxide Electronics. SMALL SCIENCE 2021. [DOI: 10.1002/smsc.202100087] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Jie Zhang
- Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
| | - Yun-Yi Pai
- Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
| | - Jason Lapano
- Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
| | - Alessandro R. Mazza
- Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
| | - Ho Nyung Lee
- Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
| | - Rob G. Moore
- Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
| | - Benjamin J. Lawrie
- Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
| | - T. Zac Ward
- Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
| | - Gyula Eres
- Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
| | - Valentino R. Cooper
- Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
| | - Matthew Brahlek
- Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA
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32
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Thees M, Lee MH, Bouwmeester RL, Rezende-Gonçalves PH, David E, Zimmers A, Fortuna F, Frantzeskakis E, Vargas NM, Kalcheim Y, Le Fèvre P, Horiba K, Kumigashira H, Biermann S, Trastoy J, Rozenberg MJ, Schuller IK, Santander-Syro AF. Imaging the itinerant-to-localized transmutation of electrons across the metal-to-insulator transition in V 2O 3. SCIENCE ADVANCES 2021; 7:eabj1164. [PMID: 34730993 PMCID: PMC8565841 DOI: 10.1126/sciadv.abj1164] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 09/14/2021] [Indexed: 06/13/2023]
Abstract
In solids, strong repulsion between electrons can inhibit their movement and result in a “Mott” metal-to-insulator transition (MIT), a fundamental phenomenon whose understanding has remained a challenge for over 50 years. A key issue is how the wave-like itinerant electrons change into a localized-like state due to increased interactions. However, observing the MIT in terms of the energy- and momentum-resolved electronic structure of the system, the only direct way to probe both itinerant and localized states, has been elusive. Here we show, using angle-resolved photoemission spectroscopy (ARPES), that in V2O3, the temperature-induced MIT is characterized by the progressive disappearance of its itinerant conduction band, without any change in its energy-momentum dispersion, and the simultaneous shift to larger binding energies of a quasi-localized state initially located near the Fermi level.
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Affiliation(s)
- Maximilian Thees
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
| | - Min-Han Lee
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA 92093, USA
| | - Rosa Luca Bouwmeester
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, Netherlands
| | - Pedro H. Rezende-Gonçalves
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
- Departamento de Física, Universidade Federal de Minas Gerais, Av. Pres. Antonio Carlos, 6627 Belo Horizonte, Brazil
| | - Emma David
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
| | - Alexandre Zimmers
- LPEM, ESPCI Paris, PSL Research University, CNRS, Sorbonne Université, 75005 Paris, France
| | - Franck Fortuna
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
| | - Emmanouil Frantzeskakis
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405 Orsay, France
| | - Nicolas M. Vargas
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA 92093, USA
| | - Yoav Kalcheim
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA 92093, USA
| | - Patrick Le Fèvre
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP48, 91192 Gif-sur-Yvette, France
| | - Koji Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
| | - Hiroshi Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai 980-8577, Japan
| | - Silke Biermann
- CPHT, CNRS, Ecole Polytechnique, Institut Polytechnique de Paris, F-91128 Palaiseau, France
- Collège de France, 11 place Marcelin Berthelot, 75005 Paris, France
- Department of Physics, Division of Mathematical Physics, Lund University, Professorsgatan 1, 22363 Lund, Sweden
| | - Juan Trastoy
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Sud, Université Paris-Saclay, 91767 Palaiseau, France
| | - Marcelo J. Rozenberg
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay, France
| | - Ivan K. Schuller
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA 92093, USA
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33
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Chen X, Zhang J, Liu B, Hu F, Shen B, Sun J. Two-dimensional conducting states in infinite-layer oxide/perovskite oxide hetero-structures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:035003. [PMID: 34663765 DOI: 10.1088/1361-648x/ac30b6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 10/18/2021] [Indexed: 06/13/2023]
Abstract
Heterointerfaces sandwiched by oxides of dissimilar crystal structures will show strong interface reconstruction, leading to distinct interfacial effect arising from unusual physics. Here, we present a theoretical investigation on the interfaces between infinite-layer oxide and perovskite oxide (SrCuO2/SrTiO3and SrCuO2/KTaO3). Surprisingly, we found well-defined two-dimensional electron gas (2DEG), stemming from atomic reconstruction and polar discontinuity at interface. Moreover, the 2DEG resides in both the TiO2and CuO2interfacial layers, unlike LaAlO3/SrTiO3for which 2DEG exists only in the TiO2interfacial layer. More than that, no metal-to-insulator transition is observed as the SrCuO2layer thickness decreases to one unit cell, i.e., the metallicity of the new interface is robust. Further investigations show more unique features of the 2DEG. Due to the absence of apical oxygen at the SrCuO2/SrTiO3(KTaO3) interface, the conducting states in the interface TiO2(TaO2) layer follows thedxy<d3z2-r2<dxz/yzorbital order rather than thedxy<dxz/yzorbital order of paradigm LaAlO3/SrTiO3(KTaO3), exhibiting enhanced interfacial conduction. This work suggests the great potential of heterointerfaces composed of non-isostructural oxides for fundamental research.
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Affiliation(s)
- Xiaobing Chen
- Beijing National Laboratory for Condensed Matter Physics & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Jine Zhang
- School of Integrated Circuit Science and Engineering, Beihang University, Beijing 100191, People's Republic of China
| | - Banggui Liu
- Beijing National Laboratory for Condensed Matter Physics & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Fengxia Hu
- Beijing National Laboratory for Condensed Matter Physics & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
| | - Baogen Shen
- Beijing National Laboratory for Condensed Matter Physics & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
| | - Jirong Sun
- Beijing National Laboratory for Condensed Matter Physics & Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
- Spintronics Institute, University of Jinan, Jinan, Shandong 250022, People's Republic of China
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34
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Guedes EB, Muff S, Brito WH, Caputo M, Li H, Plumb NC, Dil JH, Radović M. Universal Structural Influence on the 2D Electron Gas at SrTiO 3 Surfaces. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:e2100602. [PMID: 34532983 PMCID: PMC8596100 DOI: 10.1002/advs.202100602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 06/23/2021] [Indexed: 05/28/2023]
Abstract
The 2-dimensional electron gas (2DEG) found at the surface of SrTiO3 and related interfaces has attracted significant attention as a promising basis for oxide electronics. In order to utilize its full potential, the response of this 2DEG to structural changes and surface modification must be understood in detail. Here, a study of the detailed electronic structure evolution of the 2DEG as a function of sample temperature and surface step density is presented. By comparing the experimental results with ab initio calculations, it is shown that local structure relaxations cause a metal-insulator transition of the system around 135 K. This study presents a new and simple way of tuning the 2DEG via surface vicinality and identifies how the operation of prospective devices will respond to changes in temperature.
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Affiliation(s)
- Eduardo B. Guedes
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
| | - Stefan Muff
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
| | - Walber H. Brito
- Departamento de FísicaUniversidade Federal de Minas GeraisC.P. 702Belo HorizonteMinas Gerais30123Brazil
| | - Marco Caputo
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
- Elettra‐Sincrotrone TriesteS.C.p.A, S.S 14‐km 163.5 in AREA Science Park, BasovizzaTrieste34149Italy
| | - Hang Li
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
- Department of Energy Conversion and StorageTechnical University of DenmarkKgs. Lyngby2800Denmark
| | - Nicholas C. Plumb
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
| | - J. Hugo Dil
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
- Institut de PhysiqueÉcole Polytechnique Fédérale de LausanneLausanneCH‐1015Switzerland
| | - Milan Radović
- Photon Science DivisionPaul Scherrer InstitutVilligenCH‐5232Switzerland
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35
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Katsube D, Ohno S, Takayanagi S, Ojima S, Maeda M, Origuchi N, Ogawa A, Ikeda N, Aoyagi Y, Kabutoya Y, Kyungmin K, Linfeng H, Fengxuan L, Tsuda Y, Yoshida H, Nishi S, Sakamoto T, Inami E, Yoshigoe A, Abe M. Oxidation of Anatase TiO 2(001) Surface Using Supersonic Seeded Oxygen Molecular Beam. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:12313-12317. [PMID: 34644079 DOI: 10.1021/acs.langmuir.1c01752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We investigated the oxidation of oxygen vacancies at the surface of anatase TiO2(001) using a supersonic seeded molecular beam (SSMB) of oxygen. The oxygen vacancies at the top surface and subsurface could be eliminated by the supply of oxygen using an SSMB. Oxygen vacancies are present on the surface of anatase TiO2(001) when it is untreated before transfer to a vacuum chamber. These vacancies, which are stable in the as-grown condition, could also be effectively eliminated by using the oxygen SSMB.
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Affiliation(s)
- Daiki Katsube
- Department of Electrical, Electronics and Information Engineering, Nagaoka University of Technology, 1603-1 Kamitomiokamachi, Nagaoka, Niigata 940-2188, Japan
| | - Shinya Ohno
- Department of Physic, Faculty of Engineerings, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
| | - Shuhei Takayanagi
- Department of Physic, Faculty of Engineerings, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
| | - Shoki Ojima
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Motoyasu Maeda
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Naoki Origuchi
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Arata Ogawa
- Department of Physic, Faculty of Engineerings, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
| | - Natsuki Ikeda
- Department of Physic, Faculty of Engineerings, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
| | - Yoshihide Aoyagi
- Department of Physic, Faculty of Engineerings, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
| | - Yuito Kabutoya
- Department of Electrical, Electronics and Information Engineering, Nagaoka University of Technology, 1603-1 Kamitomiokamachi, Nagaoka, Niigata 940-2188, Japan
| | - Kim Kyungmin
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Hou Linfeng
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Li Fengxuan
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Yasutaka Tsuda
- Materials Sciences Research Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Hikaru Yoshida
- Materials Sciences Research Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Shizuka Nishi
- Materials Sciences Research Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Tetsuya Sakamoto
- Materials Sciences Research Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Eiichi Inami
- School of Systems Engineering, Kochi University of Technology, 185 Miyanokuchi, Tosayamada, Kami, Kochi 782-8502, Japan
| | - Akitaka Yoshigoe
- Materials Sciences Research Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Masayuki Abe
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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36
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Blackman C. Do We Need "Ionosorbed" Oxygen Species? (Or, "A Surface Conductivity Model of Gas Sensitivity in Metal Oxides Based on Variable Surface Oxygen Vacancy Concentration"). ACS Sens 2021; 6:3509-3516. [PMID: 34570973 DOI: 10.1021/acssensors.1c01727] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The author provides an opinion on direct experimental evidence available to support the "ionosorption theory" often employed to interpret "electrophysical" measurements made during a gas sensing experiment. This article then aims to provide an alternative framework of a "surface conductivity" model based on recent advances in theoretical and experimental investigations in solid state physics, and to use this framework as a guide toward design rules for future improvement of gas sensor performance.
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Affiliation(s)
- Christopher Blackman
- Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, United Kingdom
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37
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Lin W, Liu L, Liu Q, Li L, Shu X, Li C, Xie Q, Jiang P, Zheng X, Guo R, Lim Z, Zeng S, Zhou G, Wang H, Zhou J, Yang P, Pennycook SJ, Xu X, Zhong Z, Wang Z, Chen J. Electric Field Control of the Magnetic Weyl Fermion in an Epitaxial SrRuO 3 (111) Thin Film. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2101316. [PMID: 34302392 DOI: 10.1002/adma.202101316] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 05/17/2021] [Indexed: 06/13/2023]
Abstract
The magnetic Weyl fermion originates from the time reversal symmetry (TRS)-breaking in magnetic crystalline structures, where the topology and magnetism entangle with each other. Therefore, the magnetic Weyl fermion is expected to be effectively tuned by the magnetic field and electrical field, which holds promise for future topologically protected electronics. However, the electrical field control of the magnetic Weyl fermion has rarely been reported, which is prevented by the limited number of identified magnetic Weyl solids. Here, the electric field control of the magnetic Weyl fermion is demonstrated in an epitaxial SrRuO3 (111) thin film. The magnetic Weyl fermion in the SrRuO3 films is indicated by the chiral anomaly induced magnetotransport, and is verified by the observed Weyl nodes in the electronic structures characterized by the angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations. Through the ionic-liquid gating experiment, the effective manipulation of the Weyl fermion by electric field is demonstrated, in terms of the sign-change of the ordinary Hall effect, the nonmonotonic tuning of the anomalous Hall effect, and the observation of the linear magnetoresistance under proper gating voltages. The work may stimulate the searching and tuning of Weyl fermions in other magnetic materials, which are promising in energy-efficient electronics.
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Affiliation(s)
- Weinan Lin
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Liang Liu
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Qing Liu
- Key Laboratory of Magnetic Materials and Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China
| | - Lei Li
- Key Laboratory of Magnetic Materials and Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China
- Institute of Flexible Electronics, Northwestern Polytechnical University, Xi'an, 710072, China
| | - Xinyu Shu
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Changjian Li
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Qidong Xie
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Peiheng Jiang
- Key Laboratory of Magnetic Materials and Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China
| | - Xuan Zheng
- Key Laboratory of Magnetic Materials and Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China
- Department of Chemical and Environmental Engineering, The University of Nottingham, Ningbo, 315042, China
| | - Rui Guo
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Zhishiuh Lim
- NUSNNI-Nanocore, National University of Singapore, Singapore, 117411, Singapore
| | - Shengwei Zeng
- NUSNNI-Nanocore, National University of Singapore, Singapore, 117411, Singapore
| | - Guowei Zhou
- Key Laboratory of Magnetic Molecules and Magnetic Information Materials of Ministry of Education, School of Chemistry and Materials Science, Shanxi Normal University, Linfen, 041004, China
| | - Han Wang
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Jing Zhou
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Ping Yang
- Singapore Synchrotron Light Source (SSLS), National University of Singapore, Singapore, 117603, Singapore
| | - Stephen J Pennycook
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Xiaohong Xu
- Key Laboratory of Magnetic Molecules and Magnetic Information Materials of Ministry of Education, School of Chemistry and Materials Science, Shanxi Normal University, Linfen, 041004, China
| | - Zhicheng Zhong
- Key Laboratory of Magnetic Materials and Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China
- China Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Zhiming Wang
- Key Laboratory of Magnetic Materials and Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China
- China Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jingsheng Chen
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
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38
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Jin MJ, Um DS, Ohnishi K, Komori S, Stelmashenko N, Choe D, Yoo JW, Robinson JWA. Pure Spin Currents Driven by Colossal Spin-Orbit Coupling on Two-Dimensional Surface Conducting SrTiO 3. NANO LETTERS 2021; 21:6511-6517. [PMID: 34320314 DOI: 10.1021/acs.nanolett.1c01607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Spin accumulation is generated by passing a charge current through a ferromagnetic layer and sensed by other ferromagnetic layers downstream. Pure spin currents can also be generated in which spin currents flow and are detected as a nonlocal resistance in which the charge current is diverted away from the voltage measurement point. Here, we report nonlocal spin-transport on two-dimensional surface-conducting SrTiO3 (STO) without a ferromagnetic spin-injector via the spin Hall effect (and inverse spin Hall effect). By applying magnetic fields to the Hall bars at different angles to the nonlocal spin-diffusion, we demonstrate an anisotropic spin-signal that is consistent with a Hanle precession of a pure spin current. We extract key transport parameters for surface-conducting STO, including: a spin Hall angle of γ ≈ (0.25 ± 0.05), a spin lifetime of τ ∼ 49 ps, and a spin diffusion length of λs ≈ (1.23 ± 0.7) μm at 2 K.
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Affiliation(s)
- Mi-Jin Jin
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Doo-Seung Um
- Department of Electrical Engineering, Sejong University, Seoul 05006, Republic of Korea
| | - Kohei Ohnishi
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
- Department of Physics, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan
| | - Sachio Komori
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Nadia Stelmashenko
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
| | - Daeseong Choe
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Jung-Woo Yoo
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Jason W A Robinson
- Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom
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39
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Abstract
In recent decades, the behavior of SrTiO3 upon annealing in reducing conditions has been under intense academic scrutiny. Classically, its conductivity can be described using point defect chemistry and predicting n-type or p-type semiconducting behavior depending on oxygen activity. In contrast, many examples of metallic behavior induced by thermal reduction have recently appeared in the literature, challenging this established understanding. In this study, we aim to resolve this contradiction by demonstrating that an initially insulating, as-received SrTiO3 single crystal can indeed be reduced to a metallic state, and is even stable against room temperature reoxidation. However, once the sample has been oxidized at a high temperature, subsequent reduction can no longer be used to induce metallic behavior, but semiconducting behavior in agreement with the predictions of point defect chemistry is observed. Our results indicate that the dislocation-rich surface layer plays a decisive role and that its local chemical composition can be changed depending on annealing conditions. This reveals that the prediction of the macroscopic electronic properties of SrTiO3 is a highly complex task, and not only the current temperature and oxygen activity but also the redox history play an important role.
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40
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Fu R, Wu Z, Pan Z, Gao Z, Li Z, Kong X, Li L. Fluorine-Induced Surface Metallization for Ammonia Synthesis under Photoexcitation up to 1550 nm. Angew Chem Int Ed Engl 2021; 60:11173-11179. [PMID: 33650282 DOI: 10.1002/anie.202100572] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 02/17/2021] [Indexed: 11/10/2022]
Abstract
The first observation of surface metallization of TiO2-x induced by fluoride ions is presented. The emerging metallic states are contributed by the 3d orbital of surface Ti and the 2p orbital of surface bridging F, which are intrinsically originated from the strong electron repulsion between F- and adjacent Ti3+ . The metalized TiO2-x with reduced work function and downward band bending possesses high electron-donating power to supported Ru species via atomic-scale ohmic contacts, exhibiting unprecedented photocatalytic performances for ammonia synthesis across the entire solar spectrum region (200-1550 nm) at room temperature. Mechanism and kinetic analysis revealed that the loaded Ru could behave as efficient electron sinks to accumulate photogenerated electrons and that the metallic surface markedly enhanced the dissociation of H2 and N2 by the hot electrons generated by the visible or even infrared light irradiation.
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Affiliation(s)
- Rong Fu
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Zewen Wu
- College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China.,Centre for the Physics of Materials and Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada
| | - Ziye Pan
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Zhuoyang Gao
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Zhen Li
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Xianghua Kong
- College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China.,Centre for the Physics of Materials and Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada
| | - Lu Li
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P. R. China.,Electron Microscopy Center, Jilin University, Changchun, 130012, P. R. China
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41
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Fluorine‐Induced Surface Metallization for Ammonia Synthesis under Photoexcitation up to 1550 nm. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202100572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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42
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Jia T, Chen Z, Rebec SN, Hashimoto M, Lu D, Devereaux TP, Lee D, Moore RG, Shen Z. Magic Doping and Robust Superconductivity in Monolayer FeSe on Titanates. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:2003454. [PMID: 33977049 PMCID: PMC8097367 DOI: 10.1002/advs.202003454] [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: 09/10/2020] [Revised: 01/11/2021] [Indexed: 06/12/2023]
Abstract
The enhanced superconductivity in monolayer FeSe on titanates opens a fascinating pathway toward the rational design of high-temperature superconductors. Utilizing the state-of-the-art oxide plus chalcogenide molecular beam epitaxy systems in situ connected to a synchrotron angle-resolved photoemission spectroscope, epitaxial LaTiO3 layers with varied atomic thicknesses are inserted between monolayer FeSe and SrTiO3, for systematic modulation of interfacial chemical potential. With the dramatic increase of electron accumulation at the LaTiO3/SrTiO3 surface, providing a substantial surge of work function mismatch across the FeSe/oxide interface, the charge transfer and the superconducting gap in the monolayer FeSe are found to remain markedly robust. This unexpected finding indicate the existence of an intrinsically anchored "magic" doping within the monolayer FeSe systems.
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Affiliation(s)
- Tao Jia
- Stanford Institute for Materials and Energy SciencesSLAC National Accelerator LaboratoryMenlo ParkCA94025USA
- Departments of Physics, Applied Physics, and Materials Science and EngineeringGeballe Laboratory for Advanced MaterialsStanford UniversityStanfordCA94305USA
| | - Zhuoyu Chen
- Stanford Institute for Materials and Energy SciencesSLAC National Accelerator LaboratoryMenlo ParkCA94025USA
- Departments of Physics, Applied Physics, and Materials Science and EngineeringGeballe Laboratory for Advanced MaterialsStanford UniversityStanfordCA94305USA
| | - Slavko N. Rebec
- Stanford Institute for Materials and Energy SciencesSLAC National Accelerator LaboratoryMenlo ParkCA94025USA
- Departments of Physics, Applied Physics, and Materials Science and EngineeringGeballe Laboratory for Advanced MaterialsStanford UniversityStanfordCA94305USA
| | - Makoto Hashimoto
- Stanford Synchrotron Radiation LightsourceSLAC National Accelerator LaboratoryMenlo ParkCA94025USA
| | - Donghui Lu
- Stanford Synchrotron Radiation LightsourceSLAC National Accelerator LaboratoryMenlo ParkCA94025USA
| | - Thomas P. Devereaux
- Stanford Institute for Materials and Energy SciencesSLAC National Accelerator LaboratoryMenlo ParkCA94025USA
- Departments of Physics, Applied Physics, and Materials Science and EngineeringGeballe Laboratory for Advanced MaterialsStanford UniversityStanfordCA94305USA
| | - Dung‐Hai Lee
- Department of PhysicsUniversity of California at BerkeleyBerkeleyCA94720USA
- Materials Sciences DivisionLawrence Berkeley National LaboratoryBerkeleyCA94720USA
| | - Robert G. Moore
- Materials Science and Technology DivisionOak Ridge National LaboratoryOak RidgeTN37831USA
| | - Zhi‐Xun Shen
- Stanford Institute for Materials and Energy SciencesSLAC National Accelerator LaboratoryMenlo ParkCA94025USA
- Departments of Physics, Applied Physics, and Materials Science and EngineeringGeballe Laboratory for Advanced MaterialsStanford UniversityStanfordCA94305USA
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43
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King PDC, Picozzi S, Egdell RG, Panaccione G. Angle, Spin, and Depth Resolved Photoelectron Spectroscopy on Quantum Materials. Chem Rev 2021; 121:2816-2856. [PMID: 33346644 DOI: 10.1021/acs.chemrev.0c00616] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The role of X-ray based electron spectroscopies in determining chemical, electronic, and magnetic properties of solids has been well-known for several decades. A powerful approach is angle-resolved photoelectron spectroscopy, whereby the kinetic energy and angle of photoelectrons emitted from a sample surface are measured. This provides a direct measurement of the electronic band structure of crystalline solids. Moreover, it yields powerful insights into the electronic interactions at play within a material and into the control of spin, charge, and orbital degrees of freedom, central pillars of future solid state science. With strong recent focus on research of lower-dimensional materials and modified electronic behavior at surfaces and interfaces, angle-resolved photoelectron spectroscopy has become a core technique in the study of quantum materials. In this review, we provide an introduction to the technique. Through examples from several topical materials systems, including topological insulators, transition metal dichalcogenides, and transition metal oxides, we highlight the types of information which can be obtained. We show how the combination of angle, spin, time, and depth-resolved experiments are able to reveal "hidden" spectral features, connected to semiconducting, metallic and magnetic properties of solids, as well as underlining the importance of dimensional effects in quantum materials.
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Affiliation(s)
- Phil D C King
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, United Kingdom
| | - Silvia Picozzi
- Consiglio Nazionale delle Ricerche, CNR-SPIN, Via dei Vestini 31, Chieti 66100, Italy
| | - Russell G Egdell
- Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
| | - Giancarlo Panaccione
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy
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44
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Ma X, Cheng Z, Tian M, Liu X, Cui X, Huang Y, Tan S, Yang J, Wang B. Formation of Plasmonic Polarons in Highly Electron-Doped Anatase TiO 2. NANO LETTERS 2021; 21:430-436. [PMID: 33290081 DOI: 10.1021/acs.nanolett.0c03802] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The existence of various quasiparticles of polarons because of electron-boson couplings plays important roles in determining electron transport in titanium dioxide (TiO2), which affects a wealth of physical properties from catalysis to interfacial superconductivity. In addition to the well-defined Fröhlich polarons whose electrons are dressed by the phonon clouds, it has been theoretically predicted that electrons can also couple to their own plasmonic oscillations, namely, the plasmonic polarons. Here we experimentally demonstrate the formation of plasmonic polarons in highly doped anatase TiO2 using angle-resolved photoemission spectroscopy. Our results show that the energy separation of plasmon-loss satellites follows a dependence on √n, where n is the electron density, manifesting the characteristic of plasmonic polarons. The spectral functions enable to quantitatively evaluate the strengths of electron-plasmon and electron-phonon couplings, respectively, providing an effective approach for characterizing the interplays among different bosonic modes in the complicate many-body interactions.
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Affiliation(s)
- Xiaochuan Ma
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics (CAS), University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Zhengwang Cheng
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics (CAS), University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Mingyang Tian
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics (CAS), University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiaofeng Liu
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics (CAS), University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xuefeng Cui
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics (CAS), University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yaobo Huang
- Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201204, China
| | - Shijing Tan
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics (CAS), University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jinlong Yang
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics (CAS), University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Bing Wang
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics (CAS), University of Science and Technology of China, Hefei, Anhui 230026, China
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45
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Ye M, Hu S, Zhu Y, Zhang Y, Ke S, Xie L, Zhang Y, Hu S, Zhang D, Luo Z, Gu M, He J, Zhang P, Zhang W, Chen L. Electric Polarization Switching on an Atomically Thin Metallic Oxide. NANO LETTERS 2021; 21:144-150. [PMID: 33306405 DOI: 10.1021/acs.nanolett.0c03417] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Materials with reduced dimensions have been shown to host a wide variety of exotic properties and novel quantum states that often defy textbook wisdom. Polarization switching and metallic screening are well-known examples of mutually exclusive properties that cannot coexist in bulk solids. Here we report the fabrication of (SrRuO3)1/(BaTiO3)10 superlattices that exhibits reversible polarization switching in an atomically thin metallic layer. A multipronged investigation combining structural analyses, electrical measurements, and first-principles electronic structure calculations unravels the coexistence of two-dimensional (2D) metallicity in the SrRuO3 layer accompanied by the breaking of inversion symmetry, supporting electric polarization along the out-of-plane direction. Such a 2D ferroelectric-like metal paves a novel way to engineer a quantum multistate with unusual coexisting properties, such as ferroelectrics and metals, manipulated by external fields.
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Affiliation(s)
- Mao Ye
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Songbai Hu
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yuanmin Zhu
- Academy for Advanced Interdisciplinary Studies, Southern University of Science and Technology, Shenzhen 518055, China
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yubo Zhang
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Shanming Ke
- School of Materials Science and Engineering, Nanchang University, Nanchang 330031, China
| | - Lin Xie
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yuan Zhang
- School of Materials Science and Engineering, Xiangtan University, Hunan 411105, China
| | - Sixia Hu
- Core Research Facilities, Southern University of Science and Technology, Shenzhen 518055, China
| | - Dongwen Zhang
- College of Science, National University of Defense Technology, Hunan 410073, China
| | - Zhenlin Luo
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Meng Gu
- Academy for Advanced Interdisciplinary Studies, Southern University of Science and Technology, Shenzhen 518055, China
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Jiaqing He
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Peihong Zhang
- Department of Physics, State University of New York at Buffalo, Buffalo, New York 14260, United States
| | - Wenqing Zhang
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Lang Chen
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
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46
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Thesing A, Damiani EJ, Loguercio LF, Demingos PG, Muniz AR, Carreño NLV, Khan S, Santos MJL, Brolo AG, Santos JFL. Peering into the Formation of Template-Free Hierarchical Flowerlike Nanostructures of SrTiO 3. ACS OMEGA 2020; 5:33007-33016. [PMID: 33403262 PMCID: PMC7774077 DOI: 10.1021/acsomega.0c04343] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Accepted: 12/03/2020] [Indexed: 06/12/2023]
Abstract
The development of efficient advanced functional materials is highly dependent on properties such as morphology, crystallinity, and surface functionality. In this work, hierarchical flowerlike nanostructures of SrTiO3 have been synthesized by a simple template-free solvothermal method involving poly(vinylpyrrolidone) (PVP). Molecular dynamics simulations supported by structural characterization have shown that PVP preferentially adsorbs on {110} facets, thereby promoting the {100} facet growth. This interaction results in the formation of hierarchical flowerlike nanostructures with assembled nanosheets. The petal morphology is strongly dependent on the presence of PVP, and the piling up of nanosheets, leading to nanocubes, is observed when PVP is removed at high temperatures. This work contributes to a better understanding of how to control the morphological properties of SrTiO3, which is fundamental to the synthesis of perovskite-type materials with tailored properties.
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Affiliation(s)
- Anderson Thesing
- Centro
de Tecnologias Estratégicas do Nordeste, Av. Prof. Luís Freire 1, Recife, Pernambuco 50740-545, Brazil
| | - Eduardo J. Damiani
- Instituto
de Química, Universidade Federal
do Rio Grande do Sul, Av. Bento Gonçalves 9500, CP 15003, Porto Alegre, Rio Grande do Sul 91501-970, Brazil
| | - Lara F. Loguercio
- Programa
de Pós-graduação em Ciência dos Materiais, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500,
CP 15003, Porto Alegre, Rio
Grande do Sul 91501-970, Brazil
| | - Pedro G. Demingos
- Departamento
de Engenharia Química, Universidade
Federal do Rio Grande do Sul, Rua Engenheiro Luiz Englert s/n, Porto Alegre, Rio Grande do Sul 90040-040, Brazil
| | - André R. Muniz
- Departamento
de Engenharia Química, Universidade
Federal do Rio Grande do Sul, Rua Engenheiro Luiz Englert s/n, Porto Alegre, Rio Grande do Sul 90040-040, Brazil
| | - Neftali L. V. Carreño
- Centro
de Desenvolvimento Tecnológico, Universidade
Federal de Pelotas, Rua
Gomes Carneiro 1, Pelotas, Rio Grande do Sul 96010-610, Brazil
| | - Sherdil Khan
- Instituto
de Física, Universidade Federal do
Rio Grande do Sul, Av. Bento Gonçalves 9500, CP 15003, Porto Alegre, Rio Grande do Sul 91501-970, Brazil
| | - Marcos J. L. Santos
- Instituto
de Química, Universidade Federal
do Rio Grande do Sul, Av. Bento Gonçalves 9500, CP 15003, Porto Alegre, Rio Grande do Sul 91501-970, Brazil
| | - Alexandre G. Brolo
- Department
of Chemistry and Center for Advanced Materials and Related Technologies, University of Victoria, P.O. Box 3065, Victoria, British Columbia V8W 3V6, Canada
| | - Jacqueline F. L. Santos
- Instituto
de Química, Universidade Federal
do Rio Grande do Sul, Av. Bento Gonçalves 9500, CP 15003, Porto Alegre, Rio Grande do Sul 91501-970, Brazil
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47
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Kataoka N, Tanaka M, Hosoda W, Taniguchi T, Fujimori SI, Wakita T, Muraoka Y, Yokoya T. Soft x-ray irradiation induced metallization of layered TiNCl. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:035501. [PMID: 32977314 DOI: 10.1088/1361-648x/abbbc3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 09/25/2020] [Indexed: 06/11/2023]
Abstract
We have performed soft x-ray spectroscopy in order to study the photoirradiation time dependence of the valence band structure and chemical states of layered transition metal nitride chloride TiNCl. Under the soft x-ray irradiation, the intensities of the states near the Fermi level (EF) and the Ti3+component increased, while the Cl 2pintensity decreased. Ti 2p-3dresonance photoemission spectroscopy confirmed a distinctive Fermi edge with Ti 3dcharacter. These results indicate the photo-induced metallization originates from deintercalation due to Cl desorption, and thus provide a new carrier doping method that controls the conducting properties of TiNCl.
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Affiliation(s)
- Noriyuki Kataoka
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Masashi Tanaka
- Graduate School of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan
| | - Wataru Hosoda
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Takumi Taniguchi
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Shin-Ichi Fujimori
- Materials Sciences Research Center, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan
| | - Takanori Wakita
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Yuji Muraoka
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
| | - Takayoshi Yokoya
- Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
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48
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Abstract
SrTiO3 is an insulating material which, using chemical doping, pressure, strain or isotope substitution, can be turned into a ferroelectric material or into a superconductor. The material itself, and the two aforementioned phenomena, have been subjects of intensive research of Karl Alex Müller and have been a source of inspiration, among other things, for his Nobel prize-winning research on high temperature superconductivity. An intriguing outstanding question is whether the occurrence of ferroelectricity and superconductivity in the same material is just a coincidence, or whether a deeper connection exists. In addition there is the empirical question of how these two phenomena interact with each other. Here we show that it is possible to induce superconductivity in a two-dimensional layer at the interface of SrTiO3 and LaAlO3 when we make the SrTiO3 ferroelectric by means of 18O substitution. Our experiments indicate that the ferroelectricity is perfectly compatible with having a superconducting two-dimensional electron system at the interface. This provides a promising avenue for manipulating superconductivity in a non centrosymmetric environment.
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49
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Shi XL, Zou J, Chen ZG. Advanced Thermoelectric Design: From Materials and Structures to Devices. Chem Rev 2020; 120:7399-7515. [PMID: 32614171 DOI: 10.1021/acs.chemrev.0c00026] [Citation(s) in RCA: 359] [Impact Index Per Article: 89.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The long-standing popularity of thermoelectric materials has contributed to the creation of various thermoelectric devices and stimulated the development of strategies to improve their thermoelectric performance. In this review, we aim to comprehensively summarize the state-of-the-art strategies for the realization of high-performance thermoelectric materials and devices by establishing the links between synthesis, structural characteristics, properties, underlying chemistry and physics, including structural design (point defects, dislocations, interfaces, inclusions, and pores), multidimensional design (quantum dots/wires, nanoparticles, nanowires, nano- or microbelts, few-layered nanosheets, nano- or microplates, thin films, single crystals, and polycrystalline bulks), and advanced device design (thermoelectric modules, miniature generators and coolers, and flexible thermoelectric generators). The outline of each strategy starts with a concise presentation of their fundamentals and carefully selected examples. In the end, we point out the controversies, challenges, and outlooks toward the future development of thermoelectric materials and devices. Overall, this review will serve to help materials scientists, chemists, and physicists, particularly students and young researchers, in selecting suitable strategies for the improvement of thermoelectrics and potentially other relevant energy conversion technologies.
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Affiliation(s)
- Xiao-Lei Shi
- Centre for Future Materials, University of Southern Queensland, Springfield Central, Queensland 4300, Australia.,School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Jin Zou
- School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia.,Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Zhi-Gang Chen
- Centre for Future Materials, University of Southern Queensland, Springfield Central, Queensland 4300, Australia.,School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, Queensland 4072, Australia
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Chen Y, Lechaux Y, Casals B, Guillet B, Minj A, Gázquez J, Méchin L, Herranz G. Photoinduced Persistent Electron Accumulation and Depletion in LaAlO_{3}/SrTiO_{3} Quantum Wells. PHYSICAL REVIEW LETTERS 2020; 124:246804. [PMID: 32639817 DOI: 10.1103/physrevlett.124.246804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 05/14/2020] [Indexed: 06/11/2023]
Abstract
Persistent photoconductance is a phenomenon found in many semiconductors, by which light induces long-lived excitations in electronic states. Commonly, persistent photoexcitation leads to an increase of carriers (accumulation), though occasionally it can be negative (depletion). Here, we present the quantum well at the LaAlO_{3}/SrTiO_{3} interface, where in addition to photoinduced accumulation, a secondary photoexcitation enables carrier depletion. The balance between both processes is wavelength dependent, and allows tunable accumulation or depletion in an asymmetric manner, depending on the relative arrival time of photons of different frequencies. We use Green's function formalism to describe this unconventional photoexcitation, which paves the way to an optical implementation of neurobiologically inspired spike-timing-dependent plasticity.
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Affiliation(s)
- Yu Chen
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
| | - Yoann Lechaux
- Normandie Univ, UNICAEN, ENSICAEN, CNRS, GREYC, 14000 Caen, France
| | - Blai Casals
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
| | - Bruno Guillet
- Normandie Univ, UNICAEN, ENSICAEN, CNRS, GREYC, 14000 Caen, France
| | - Albert Minj
- Normandie Univ, UNICAEN, ENSICAEN, CNRS, GREYC, 14000 Caen, France
- IMEC, Kapeldreef 75, Leuven 3000, Belgium
| | - Jaume Gázquez
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
| | - Laurence Méchin
- Normandie Univ, UNICAEN, ENSICAEN, CNRS, GREYC, 14000 Caen, France
| | - Gervasi Herranz
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Catalonia, Spain
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