1
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Sinclair J, Flores M, Brugh AM, Rajh T, Juelsholt M, Riaz AA, Schlueter C, Regoutz A, Birkel CS. In-Depth Analysis of the Species and Transformations during Sol Gel-Assisted V 2PC Synthesis. Inorg Chem 2024; 63:10682-10690. [PMID: 38787450 DOI: 10.1021/acs.inorgchem.4c01160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
The sol-gel reaction mechanism of 211 MAX phases has proven to be very complex when identifying the intermediate species, chemical processes, and conversions that occur from a mixture of metal salts and gelling agent into a crystalline ternary carbide. With mostly qualitative results in the literature (Cr2GaC, Cr2GeC, and V2GeC), additional analytical techniques, including thermal analysis, powder diffraction, total scattering, and various spectroscopic methods, are necessary to unravel the identity of the chemical compounds and transformations during the reaction. Here, we demonstrate the combination of these techniques to understand the details of the sol-gel synthesis of MAX phase V2PC. The metal phosphate complexes, as well as amorphous/nanocrystalline vanadium phosphate species (V in different oxidation states), are identified at all stages of the reaction and a full schematic of the reaction process is suggested. The early amorphous vanadium species undergo multiple changes of oxidation states while organic species decompose releasing a variety of small molecule gases. Amorphous oxides, analogous to [NH4][VO2][HPO4], V2PO4O, and VO2P2O7 are identified in the dried gel obtained during the early stages of the heating process (300 and 600 °C), respectively. They are carbothermally reduced starting at 900 °C and subsequently react to crystalline V2PC with the excess carbon in the reaction mixture. Through CHN analysis, we obtain an estimate of left-over amorphous carbon in the product which will guide future efforts of minimizing the amount of carbon in sol gel-produced MAX phases which is important for subsequent property studies.
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Affiliation(s)
- Jordan Sinclair
- School of Molecular Sciences, Arizona State University, Tempe AZ-85282, United States
| | - Marco Flores
- School of Molecular Sciences, Arizona State University, Tempe AZ-85282, United States
| | - Alexander M Brugh
- School of Molecular Sciences, Arizona State University, Tempe AZ-85282, United States
| | - Tijana Rajh
- School of Molecular Sciences, Arizona State University, Tempe AZ-85282, United States
| | - Mikkel Juelsholt
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Aysha A Riaz
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | | | - Anna Regoutz
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - Christina S Birkel
- School of Molecular Sciences, Arizona State University, Tempe AZ-85282, United States
- Department of Chemistry and Biochemistry, Technische Universität Darmstadt, 64283 Darmstadt, Germany
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2
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Mondal D, Mahapatra SR, Derrico AM, Rai RK, Paudel JR, Schlueter C, Gloskovskii A, Banerjee R, Hariki A, DeGroot FMF, Sarma DD, Narayan A, Nukala P, Gray AX, Aetukuri NPB. Modulation-doping a correlated electron insulator. Nat Commun 2023; 14:6210. [PMID: 37798279 PMCID: PMC10556139 DOI: 10.1038/s41467-023-41816-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 09/13/2023] [Indexed: 10/07/2023] Open
Abstract
Correlated electron materials (CEMs) host a rich variety of condensed matter phases. Vanadium dioxide (VO2) is a prototypical CEM with a temperature-dependent metal-to-insulator (MIT) transition with a concomitant crystal symmetry change. External control of MIT in VO2-especially without inducing structural changes-has been a long-standing challenge. In this work, we design and synthesize modulation-doped VO2-based thin film heterostructures that closely emulate a textbook example of filling control in a correlated electron insulator. Using a combination of charge transport, hard X-ray photoelectron spectroscopy, and structural characterization, we show that the insulating state can be doped to achieve carrier densities greater than 5 × 1021 cm-3 without inducing any measurable structural changes. We find that the MIT temperature (TMIT) continuously decreases with increasing carrier concentration. Remarkably, the insulating state is robust even at doping concentrations as high as ~0.2 e-/vanadium. Finally, our work reveals modulation-doping as a viable method for electronic control of phase transitions in correlated electron oxides with the potential for use in future devices based on electric-field controlled phase transitions.
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Affiliation(s)
- Debasish Mondal
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India
| | - Smruti Rekha Mahapatra
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India
| | | | - Rajeev Kumar Rai
- Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore, Karnataka, India
| | - Jay R Paudel
- Department of Physics, Temple University, Philadelphia, PA, USA
| | | | | | - Rajdeep Banerjee
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India
| | - Atsushi Hariki
- Department of Physics and Electronics, Graduate School of Engineering, Osaka Metropolitan University, Osaka, Japan
| | - Frank M F DeGroot
- Utrecht University, Inorganic Chemistry and Catalysis Group Universiteitsweg 99, Utrecht, The Netherlands
| | - D D Sarma
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India
| | - Awadhesh Narayan
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India
| | - Pavan Nukala
- Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore, Karnataka, India
| | - Alexander X Gray
- Department of Physics, Temple University, Philadelphia, PA, USA.
| | - Naga Phani B Aetukuri
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India.
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3
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Birkhölzer YA, Sotthewes K, Gauquelin N, Riekehr L, Jannis D, van der Minne E, Bu Y, Verbeeck J, Zandvliet HJW, Koster G, Rijnders G. High-Strain-Induced Local Modification of the Electronic Properties of VO 2 Thin Films. ACS APPLIED ELECTRONIC MATERIALS 2022; 4:6020-6028. [PMID: 36588623 PMCID: PMC9798830 DOI: 10.1021/acsaelm.2c01176] [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: 09/05/2022] [Accepted: 11/07/2022] [Indexed: 06/17/2023]
Abstract
Vanadium dioxide (VO2) is a popular candidate for electronic and optical switching applications due to its well-known semiconductor-metal transition. Its study is notoriously challenging due to the interplay of long- and short-range elastic distortions, as well as the symmetry change and the electronic structure changes. The inherent coupling of lattice and electronic degrees of freedom opens the avenue toward mechanical actuation of single domains. In this work, we show that we can manipulate and monitor the reversible semiconductor-to-metal transition of VO2 while applying a controlled amount of mechanical pressure by a nanosized metallic probe using an atomic force microscope. At a critical pressure, we can reversibly actuate the phase transition with a large modulation of the conductivity. Direct tunneling through the VO2-metal contact is observed as the main charge carrier injection mechanism before and after the phase transition of VO2. The tunneling barrier is formed by a very thin but persistently insulating surface layer of the VO2. The necessary pressure to induce the transition decreases with temperature. In addition, we measured the phase coexistence line in a hitherto unexplored regime. Our study provides valuable information on pressure-induced electronic modifications of the VO2 properties, as well as on nanoscale metal-oxide contacts, which can help in the future design of oxide electronics.
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Affiliation(s)
- Yorick A. Birkhölzer
- MESA+
Institute of Nanotechnology, University
of Twente, P.O. Box 217, 7500AEEnschede, The Netherlands
| | - Kai Sotthewes
- MESA+
Institute of Nanotechnology, University
of Twente, P.O. Box 217, 7500AEEnschede, The Netherlands
| | - Nicolas Gauquelin
- Electron
Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020Antwerp, Belgium
| | - Lars Riekehr
- Electron
Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020Antwerp, Belgium
| | - Daen Jannis
- Electron
Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020Antwerp, Belgium
| | - Emma van der Minne
- MESA+
Institute of Nanotechnology, University
of Twente, P.O. Box 217, 7500AEEnschede, The Netherlands
| | - Yibin Bu
- MESA+
Institute of Nanotechnology, University
of Twente, P.O. Box 217, 7500AEEnschede, The Netherlands
| | - Johan Verbeeck
- Electron
Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020Antwerp, Belgium
| | - Harold J. W. Zandvliet
- MESA+
Institute of Nanotechnology, University
of Twente, P.O. Box 217, 7500AEEnschede, The Netherlands
| | - Gertjan Koster
- MESA+
Institute of Nanotechnology, University
of Twente, P.O. Box 217, 7500AEEnschede, The Netherlands
| | - Guus Rijnders
- MESA+
Institute of Nanotechnology, University
of Twente, P.O. Box 217, 7500AEEnschede, The Netherlands
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4
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Lu Q, Sohn C, Hu G, Gao X, Chisholm MF, Kylänpää I, Krogel JT, Kent PRC, Heinonen O, Ganesh P, Lee HN. Metal-insulator transition tuned by oxygen vacancy migration across TiO 2/VO 2 interface. Sci Rep 2020; 10:18554. [PMID: 33122724 PMCID: PMC7596522 DOI: 10.1038/s41598-020-75695-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 10/14/2020] [Indexed: 01/17/2023] Open
Abstract
Oxygen defects are essential building blocks for designing functional oxides with remarkable properties, ranging from electrical and ionic conductivity to magnetism and ferroelectricity. Oxygen defects, despite being spatially localized, can profoundly alter global properties such as the crystal symmetry and electronic structure, thereby enabling emergent phenomena. In this work, we achieved tunable metal–insulator transitions (MIT) in oxide heterostructures by inducing interfacial oxygen vacancy migration. We chose the non-stoichiometric VO2-δ as a model system due to its near room temperature MIT temperature. We found that depositing a TiO2 capping layer on an epitaxial VO2 thin film can effectively reduce the resistance of the insulating phase in VO2, yielding a significantly reduced ROFF/RON ratio. We systematically studied the TiO2/VO2 heterostructures by structural and transport measurements, X-ray photoelectron spectroscopy, and ab initio calculations and found that oxygen vacancy migration from TiO2 to VO2 is responsible for the suppression of the MIT. Our findings underscore the importance of the interfacial oxygen vacancy migration and redistribution in controlling the electronic structure and emergent functionality of the heterostructure, thereby providing a new approach to designing oxide heterostructures for novel ionotronics and neuromorphic-computing devices.
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Affiliation(s)
- Qiyang Lu
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.,School of Engineering, Westlake University, Hangzhou, 310024, Zhejiang, China
| | - Changhee Sohn
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Guoxiang Hu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Xiang Gao
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Matthew F Chisholm
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Ilkka Kylänpää
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.,Computational Physics Laboratory, Tampere University, P.O. Box 692, 33014, Tampere, Finland
| | - Jaron T Krogel
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Paul R C Kent
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.,Computational Science and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Olle Heinonen
- Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - P Ganesh
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Ho Nyung Lee
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
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5
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Yang Y, Yao Y, Zhang B, Lin H, Luo Z, Gao C, Zhang C, Kang C. Investigating Metal⁻Insulator Transition and Structural Phase Transformation in the (010)-VO₂/(001)-YSZ Epitaxial Thin Films. MATERIALS 2018; 11:ma11091713. [PMID: 30217052 PMCID: PMC6163228 DOI: 10.3390/ma11091713] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Revised: 09/05/2018] [Accepted: 09/11/2018] [Indexed: 11/16/2022]
Abstract
The VO2 thin films with sharp metal–insulator transition (MIT) were epitaxially grown on (001)-oriented Yttria-stabilized zirconia substrates (YSZ) using radio-frequency (RF) magnetron sputtering techniques. The MIT and structural phase transition (SPT) were comprehensively investigated under in situ temperature conditions. The amplitude of MIT is in the order of magnitude of 104, and critical temperature is 342 K during the heating cycle. It is interesting that both electron concentration and mobility are changed by two orders of magnitude across the MIT. This research is distinctively different from previous studies, which found that the electron concentration solely contributes to the amplitude of the MIT, although the electron mobility does not. Analysis of the SPT showed that the (010)-VO2/(001)-YSZ epitaxial thin film presents a special multi-domain structure, which is probably due to the symmetry matching and lattice mismatch between the VO2 and YSZ substrate. The VO2 film experiences the SPT from the M1 phase at low temperature to a rutile phase at a high temperature. Moreover, the SPT occurs at the same critical temperature as that of the MIT. This work may shed light on a new MIT behavior and may potentially pave the way for preparing high-quality VO2 thin films on cost-effective YSZ substrates for photoelectronic applications.
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Affiliation(s)
- Yuanjun Yang
- School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009, China.
| | - Yingxue Yao
- School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009, China.
| | - Benjian Zhang
- School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009, China.
| | - Hui Lin
- School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009, China.
| | - Zhenlin Luo
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China.
| | - Chen Gao
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China.
| | - Cong Zhang
- School of Physics and Electronic Information, Henan Polytechnic University, Jiaozuo 454000, China.
| | - Chaoyang Kang
- School of Physics and Electronic Information, Henan Polytechnic University, Jiaozuo 454000, China.
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6
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Zhang D, Sun HJ, Wang MH, Miao LH, Liu HZ, Zhang YZ, Bian JM. VO₂ Thermochromic Films on Quartz Glass Substrate Grown by RF-Plasma-Assisted Oxide Molecular Beam Epitaxy. MATERIALS 2017; 10:ma10030314. [PMID: 28772673 PMCID: PMC5503335 DOI: 10.3390/ma10030314] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2017] [Revised: 03/14/2017] [Accepted: 03/15/2017] [Indexed: 11/17/2022]
Abstract
Vanadium dioxide (VO2) thermochromic thin films with various thicknesses were grown on quartz glass substrates by radio frequency (RF)-plasma assisted oxide molecular beam epitaxy (O-MBE). The crystal structure, morphology and chemical stoichiometry were investigated systemically by X-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses. An excellent reversible metal-to-insulator transition (MIT) characteristics accompanied by an abrupt change in both electrical resistivity and optical infrared (IR) transmittance was observed from the optimized sample. Remarkably, the transition temperature (TMIT) deduced from the resistivity-temperature curve was reasonably consistent with that obtained from the temperature-dependent IR transmittance. Based on Raman measurement and XPS analyses, the observations were interpreted in terms of residual stresses and chemical stoichiometry. This achievement will be of great benefit for practical application of VO2-based smart windows.
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Affiliation(s)
- Dong Zhang
- New Energy Source Research Center, Shenyang Institute of Engineering, Shenyang 110136, China.
| | - Hong-Jun Sun
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams(Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China.
| | - Min-Huan Wang
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams(Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China.
| | - Li-Hua Miao
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams(Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China.
| | - Hong-Zhu Liu
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams(Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China.
| | - Yu-Zhi Zhang
- Key Laboratory of Inorganic Coating Materials, Chinese Academy of Sciences, Shanghai 200050, China.
| | - Ji-Ming Bian
- New Energy Source Research Center, Shenyang Institute of Engineering, Shenyang 110136, China.
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams(Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China.
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