1
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Prifti E, Buban JP, Thind AS, Klie RF. Variational Convolutional Autoencoders for Anomaly Detection in Scanning Transmission Electron Microscopy. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2205977. [PMID: 36651114 DOI: 10.1002/smll.202205977] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 12/08/2022] [Indexed: 06/17/2023]
Abstract
Identifying point defects and other structural anomalies using scanning transmission electron microscopy (STEM) is important to understand a material's properties caused by the disruption of the regular pattern of crystal lattice. Due to improvements in instrumentation stability and electron optics, atomic-resolution images with a field of view of several hundred nanometers can now be routinely acquired at 1-10 Hz frame rates and such data, which often contain thousands of atomic columns, need to be analyzed. To date, image analysis is performed largely manually, but recent developments in computer vision (CV) and machine learning (ML) now enable automated analysis of atomic structures and associated defects. Here, the authors report on how a Convolutional Variational Autoencoder (CVAE) can be utilized to detect structural anomalies in atomic-resolution STEM images. Specifically, the training set is limited to perfect crystal images , and the performance of a CVAE in differentiating between single-crystal bulk data or point defects is demonstrated. It is found that the CVAE can reproduce the perfect crystal data but not the defect input data. The disagreesments between the CVAE-predicted data for defects allows for a clear and automatic distinction and differentiation of several point defect types.
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Affiliation(s)
- Enea Prifti
- Department of Physics, University of Illinois Chicago, 845 W Taylor Street, Chicago, IL, 60607, USA
| | - James P Buban
- Department of Physics, University of Illinois Chicago, 845 W Taylor Street, Chicago, IL, 60607, USA
| | - Arashdeep Singh Thind
- Department of Physics, University of Illinois Chicago, 845 W Taylor Street, Chicago, IL, 60607, USA
| | - Robert F Klie
- Department of Physics, University of Illinois Chicago, 845 W Taylor Street, Chicago, IL, 60607, USA
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2
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Zhao B, Yan Z, Du Y, Rao L, Chen G, Wu Y, Yang L, Zhang J, Wu L, Zhang DW, Che R. High-Entropy Enhanced Microwave Attenuation in Titanate Perovskites. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2210243. [PMID: 36606342 DOI: 10.1002/adma.202210243] [Citation(s) in RCA: 46] [Impact Index Per Article: 46.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Revised: 12/01/2022] [Indexed: 06/17/2023]
Abstract
High-entropy oxides (HEOs), which incorporate multiple-principal cations into single-phase crystals and interact with diverse metal ions, extend the border for available compositions and unprecedented properties. Herein, a high-entropy-stabilized (Ca0.2 Sr0.2 Ba0.2 La0.2 Pb0.2 )TiO3 perovskite is reported, and the effective absorption bandwidth (90% absorption) improves almost two times than that of BaTiO3 . The results demonstrate that the regulation of entropy configuration can yield significant grain boundaries, oxygen defects, and an ultradense distorted lattice. These characteristics give rise to strong interfacial and defect-induced polarizations, thus synergistically contributing to the dielectric attenuation performance. Moreover, the large strains derived from the strong lattice distortions in the high-entropy perovskite offer varied transport for electron carriers. The high-entropy-enhanced positive/negative charges accumulation around grain boundaries and strain-concentrated location, quantitatively validated by electron holography, results in unusual dielectric polarization loss. This study opens up an effective avenue for designing strong microwave absorption materials to satisfy the increasingly demanding requirements of advanced and integrated electronics. This work also offers a paradigm for improving other interesting properties for HEOs through entropy engineering.
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Affiliation(s)
- Biao Zhao
- School of Microelectronics, Fudan University, Shanghai, 2000433, P. R. China
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai, 200438, P. R. China
| | - Zhikai Yan
- Henan Key Laboratory of Aeronautical Materials and Application Technology, School of Material Science and Engineering, Zhengzhou University of Aeronautics, Zhengzhou, Henan, 450046, P. R. China
| | - Yiqian Du
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai, 200438, P. R. China
| | - Longjun Rao
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai, 200438, P. R. China
| | - Guanyu Chen
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai, 200438, P. R. China
| | - Yuyang Wu
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai, 200438, P. R. China
| | - Liting Yang
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai, 200438, P. R. China
| | | | - Limin Wu
- Inner Mongolia University, Hohhot, 010021, P. R. China
| | - David Wei Zhang
- School of Microelectronics, Fudan University, Shanghai, 2000433, P. R. China
| | - Renchao Che
- School of Microelectronics, Fudan University, Shanghai, 2000433, P. R. China
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai, 200438, P. R. China
- Zhejiang Laboratory, Hangzhou, 311100, P. R. China
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3
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Hoglund ER, Bao DL, O'Hara A, Pfeifer TW, Hoque MSB, Makarem S, Howe JM, Pantelides ST, Hopkins PE, Hachtel JA. Direct Visualization of Localized Vibrations at Complex Grain Boundaries. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2208920. [PMID: 36634374 DOI: 10.1002/adma.202208920] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 11/25/2022] [Indexed: 06/17/2023]
Abstract
Grain boundaries (GBs) are a prolific microstructural feature that dominates the functionality of a wide class of materials. The functionality at a GB results from the unique atomic arrangements, different from those in the grain, that have driven extensive experimental and theoretical studies correlating atomic-scale GB structures to macroscopic electronic, infrared optical, and thermal properties. In this work, a SrTiO3 GB is examined using atomic-resolution aberration-corrected scanning transmission electron microscopy and ultrahigh-energy-resolution monochromated electron energy-loss spectroscopy, in conjunction with density functional theory. This combination enables the correlation of the GB structure, nonstoichiometry, and chemical bonding with a redistribution of vibrational states within the GB dislocation cores. The new experimental access to localized GB vibrations provides a direct route to quantifying the impact of individual boundaries on macroscopic properties.
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Affiliation(s)
- Eric R Hoglund
- Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - De-Liang Bao
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, 37235, USA
| | - Andrew O'Hara
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, 37235, USA
| | - Thomas W Pfeifer
- Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - Md Shafkat Bin Hoque
- Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - Sara Makarem
- Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - James M Howe
- Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - Sokrates T Pantelides
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, 37235, USA
| | - Patrick E Hopkins
- Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - Jordan A Hachtel
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
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4
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Futazuka T, Ishikawa R, Shibata N, Ikuhara Y. Grain boundary structural transformation induced by co-segregation of aliovalent dopants. Nat Commun 2022; 13:5299. [PMID: 36109492 PMCID: PMC9477882 DOI: 10.1038/s41467-022-32935-4] [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: 04/07/2022] [Accepted: 08/24/2022] [Indexed: 11/10/2022] Open
Abstract
Impurity doping is a conventional but one of the most effective ways to control the functional properties of materials. In insulating materials, the dopant solubility limit is considerably low in general, and the dopants often segregate to grain boundaries (GBs) in polycrystals, which significantly alter their entire properties. However, detailed mechanisms on how dopant atoms form structures at GBs and change their properties remain a matter of conjecture. Here, we show GB structural transformation in α-Al2O3 induced by co-segregation of Ca and Si aliovalent dopants using atomic-resolution scanning transmission electron microscopy combined with density functional theory calculations. To accommodate large-sized Ca ions at the GB core, the pristine GB atomic structure is transformed into a new GB structure with larger free volumes. Moreover, the Si and Ca dopants form a chemically ordered structure, and the charge compensation is achieved within the narrow GB core region rather than forming broader space charge layers. Our findings give an insight into GB engineering by utilizing aliovalent co-segregation. The effect of aliovalent doping on grain boundary is not yet fully understood at the atomic level. Here, the authors report grain boundary structural transformation in α-Al2O3 is induced by co-segregation of multiple dopants using atomic-resolution electron microscopy and theoretical calculations.
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5
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Randall C, Yousefian P. Fundamentals and practical dielectric implications of stoichiometry and chemical design in a high-performance ferroelectric oxide: BaTiO3. Ann Ital Chir 2022. [DOI: 10.1016/j.jeurceramsoc.2021.12.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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6
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Yang C, Wang Y, Sigle W, van Aken PA. Determination of Grain-Boundary Structure and Electrostatic Characteristics in a SrTiO 3 Bicrystal by Four-Dimensional Electron Microscopy. NANO LETTERS 2021; 21:9138-9145. [PMID: 34672612 PMCID: PMC8587898 DOI: 10.1021/acs.nanolett.1c02960] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The grain boundary (GB) plays a critical role in a material's properties and device performance. Therefore, the characterization of a GB's atomic structure and electrostatic characteristics is a matter of great importance for materials science. Here, we report on the atomic structure and electrostatic analysis of a GB in a SrTiO3 bicrystal by four-dimensional scanning transmission electron microscopy (4D-STEM). We demonstrate that the Σ5 GB is Ti-rich and poor in Sr. We investigate possible effects on the variation in the atomic electrostatic field, including oxygen vacancies, Ti-valence change, and accumulation of cations. A negative charge resulting from a space-charge zone in SrTiO3 compensates a positive charge accumulated at the GB, which is in agreement with the double-Schottky-barrier model. It demonstrates the feasibility of characterizing the electrostatic properties at the nanometer scale by 4D-STEM, which provides comprehensive insights to understanding the GB structure and its concomitant effects on the electrostatic properties.
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Affiliation(s)
- Chao Yang
- Max
Planck Institute for Solid State Research, Stuttgart 70569, Germany
| | - Yi Wang
- Max
Planck Institute for Solid State Research, Stuttgart 70569, Germany
- Center
for Microscopy and Analysis, Nanjing University
of Aeronautics and Astronautics, Nanjing 210016, P.R. China
| | - Wilfried Sigle
- Max
Planck Institute for Solid State Research, Stuttgart 70569, Germany
| | - Peter A. van Aken
- Max
Planck Institute for Solid State Research, Stuttgart 70569, Germany
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7
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Effect of Reduced Atmosphere Sintering on Blocking Grain Boundaries in Rare-Earth Doped Ceria. INORGANICS 2021. [DOI: 10.3390/inorganics9080063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Rare-earth doped ceria materials are amongst the top choices for use in electrolytes and composite electrodes in intermediate temperature solid oxide fuel cells. Trivalent acceptor dopants such as gadolinium, which mediate the ionic conductivity in ceria by creating oxygen vacancies, have a tendency to segregate at grain boundaries and triple points. This leads to formation of ionically resistive blocking grain boundaries and necessitates high operating temperatures to overcome this barrier. In an effort to improve the grain boundary conductivity, we studied the effect of a modified sintering cycle, where 10 mol% gadolinia doped ceria was sintered under a reducing atmosphere and subsequently reoxidized. A detailed analysis of the complex impedance, conductivity, and activation energy values was performed. The analysis shows that for samples processed thus, the ionic conductivity improves when compared with conventionally processed samples sintered in air. Equivalent circuit fitting shows that this improvement in conductivity is mainly due to a drop in the grain boundary resistance. Based on comparison of activation energy values for the conventionally processed vs. reduced-reoxidized samples, this drop can be attributed to a diminished blocking effect of defect-associates at the grain boundaries.
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8
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Han B, Zhu R, Li X, Wu M, Ishikawa R, Feng B, Bai X, Ikuhara Y, Gao P. Two-Dimensional Room-Temperature Giant Antiferrodistortive SrTiO_{3} at a Grain Boundary. PHYSICAL REVIEW LETTERS 2021; 126:225702. [PMID: 34152191 DOI: 10.1103/physrevlett.126.225702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 04/23/2021] [Indexed: 06/13/2023]
Abstract
The broken symmetry at structural defects such as grain boundaries (GBs) discontinues chemical bonds, leading to the emergence of new properties that are absent in the bulk owing to the couplings between the lattice and other parameters. Here, we create a two-dimensional antiferrodistortive (AFD) strontium titanate (SrTiO_{3}) phase at a Σ13(510)/[001] SrTiO_{3} tilt GB at room temperature. We find that such an anomalous room-temperature AFD phase with the thickness of approximate six unit cells is stabilized by the charge doping from oxygen vacancies. The localized AFD originated from the strong lattice-charge couplings at a SrTiO_{3} GB is expected to play important roles in the electrical and optical activity of GBs and can explain past experiments such as the transport properties of electroceramic SrTiO_{3}. Our study also provides new strategies to create low-dimensional anomalous elements for future nanoelectronics via grain boundary engineering.
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Affiliation(s)
- Bo Han
- Electron Microscopy Laboratory and International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Ruixue Zhu
- Electron Microscopy Laboratory and International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Xiaomei Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Mei Wu
- Electron Microscopy Laboratory and International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Ryo Ishikawa
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
- Japan Science and Technology Agency, PRESTO, Kawaguchi, Saitama 332-0012, Japan
| | - Bin Feng
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - Xuedong Bai
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yuichi Ikuhara
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
- Nanostructures Research Laboratory, Japan Fine Ceramic Center, Nagoya 456-8587, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Peng Gao
- Electron Microscopy Laboratory and International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, Beijing 100871, China
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9
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Song D, Wan D, Wu HH, Xue D, Ning S, Wu M, Venkatesan T, Pennycook SJ. Electronic and plasmonic phenomena at nonstoichiometric grain boundaries in metallic SrNbO 3. NANOSCALE 2020; 12:6844-6851. [PMID: 32186322 DOI: 10.1039/c9nr10221c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Grain boundaries could exhibit exceptional electronic structure and exotic properties, which are determined by a local atomic configuration and stoichiometry that differs from the bulk. However, optical and plasmonic properties at the grain boundaries in metallic oxides have rarely been discussed before. Here, we show that non-stoichiometric grain boundaries in the newly discovered metallic SrNbO3 photocatalyst show exotic electronic, optical and plasmonic phenomena in comparison to bulk. Aberration-corrected scanning transmission electron microscopy and first-principles calculations reveal that a Nb-rich grain boundary exhibits an increased carrier concentration with quasi-1D metallic conductivity, and newly induced electronic states contributing to the broad energy range of optical absorption. More importantly, dielectric function calculations reveal extended and enhanced plasmonic excitations compared with bulk SrNbO3. Our results show that non-stoichiometric grain boundaries might be utilized to control the electronic and plasmonic properties in oxide photocatalysis.
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Affiliation(s)
- Dongsheng Song
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575.
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10
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Schwab C, Höweling A, Windmüller A, Gonzalez-Julian J, Möller S, Binder JR, Uhlenbruck S, Guillon O, Martin M. Bulk and grain boundary Li-diffusion in dense LiMn 2O 4 pellets by means of isotope exchange and ToF-SIMS analysis. Phys Chem Chem Phys 2019; 21:26066-26076. [PMID: 31746869 DOI: 10.1039/c9cp05128g] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Lithium diffusion in LiMn2O4 pellets is studied by means of isotope exchange and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). A 6Li-enriched film deposited by Pulsed Laser Deposition (PLD) on a dense LiMn2O4 pellet with natural abundance of lithium isotopes is used to study the tracer diffusion of lithium. The measured profiles are analyzed by numerical models describing the 6Li tracer diffusion from the film into the pellet. Experiments in the Harrison type B regime of diffusion kinetics allow for the distinction and simultaneous determination of bulk and grain boundary diffusion coefficients. Changing the experimental conditions to reach Harrison type A behavior yields effective diffusion coefficients for lithium tracer diffusion in LiMn2O4. Activation energies for bulk and grain boundary diffusion were obtained from experiments at different temperatures. Our values are critically compared to previous studies.
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Affiliation(s)
- C Schwab
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany.
| | - A Höweling
- Institute for Applied Materials (IAM), Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - A Windmüller
- Institute of Energy and Climate Research (IEK-1), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428 Jülich, Germany
| | - J Gonzalez-Julian
- Institute of Energy and Climate Research (IEK-1), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428 Jülich, Germany
| | - S Möller
- Institute of Energy and Climate Research (IEK-1), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428 Jülich, Germany
| | - J R Binder
- Institute for Applied Materials (IAM), Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - S Uhlenbruck
- Institute of Energy and Climate Research (IEK-1), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428 Jülich, Germany
| | - O Guillon
- Institute of Energy and Climate Research (IEK-1), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428 Jülich, Germany
| | - M Martin
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany. and Helmholtz-Institute Münster (IEK-12), Forschungszentrum Jülich GmbH, Corrensstraße 46, 48149 Münster, Germany
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11
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Kwon DH, Lee S, Kang CS, Choi YS, Kang SJ, Cho HL, Sohn W, Jo J, Lee SY, Oh KH, Noh TW, De Souza RA, Martin M, Kim M. Unraveling the Origin and Mechanism of Nanofilament Formation in Polycrystalline SrTiO 3 Resistive Switching Memories. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1901322. [PMID: 31106484 DOI: 10.1002/adma.201901322] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Indexed: 06/09/2023]
Abstract
Three central themes in the study of the phenomenon of resistive switching are the nature of the conducting phase, why it forms, and how it forms. In this study, the answers to all three questions are provided by performing switching experiments in situ in a transmission electron microscope on thin films of the model system polycrystalline SrTiO3 . On the basis of high-resolution transmission electron microscopy, electron-energy-loss spectroscopy and in situ current-voltage measurements, the conducting phase is identified to be SrTi11 O20 . This phase is only observed at specific grain boundaries, and a Ruddlesden-Popper phase, Sr3 Ti2 O7 , is typically observed adjacent to the conducting phase. These results allow not only the proposal that filament formation in this system has a thermodynamic origin-it is driven by electrochemical polarization and the local oxygen activity in the film decreasing below a critical value-but also the deduction of a phase diagram for strongly reduced SrTiO3 . Furthermore, why many conducting filaments are nucleated at one electrode but only one filament wins the race to the opposite electrode is also explained. The work thus provides detailed insights into the origin and mechanisms of filament generation and rupture.
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Affiliation(s)
- Deok-Hwang Kwon
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea
- Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Shinbuhm Lee
- Department of Emerging Materials Science, Daegu-Gyeongbuk Institute of Science and Technology, Daegu, 42988, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Chan Soon Kang
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea
- Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Yong Seok Choi
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea
- Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Sung Jin Kang
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea
- Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Hae Lim Cho
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea
- Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Woonbae Sohn
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea
- Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Janghyun Jo
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea
- Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Seung-Yong Lee
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea
- Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Kyu Hwan Oh
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea
- Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Tae Won Noh
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
| | - Roger A De Souza
- Institute of Physical Chemistry, RWTH Aachen University, Aachen, 52074, Germany
| | - Manfred Martin
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea
- Institute of Physical Chemistry, RWTH Aachen University, Aachen, 52074, Germany
| | - Miyoung Kim
- Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea
- Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
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12
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Rahman JU, Du NV, Nam WH, Shin WH, Lee KH, Seo WS, Kim MH, Lee S. Grain Boundary Interfaces Controlled by Reduced Graphene Oxide in Nonstoichiometric SrTiO 3-δ Thermoelectrics. Sci Rep 2019; 9:8624. [PMID: 31197239 PMCID: PMC6565681 DOI: 10.1038/s41598-019-45162-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Accepted: 05/24/2019] [Indexed: 11/23/2022] Open
Abstract
Point defect or doping in Strontium titanium oxide (STO) largely determines the thermoelectric (TE) properties. So far, insufficient knowledge exists on the impact of double Schottky barrier on the TE performance. Herein, we report a drastic effect of double Schottky barrier on the TE performance in undoped STO. It demonstrates that incorporation of Reduced Graphene Oxide (RGO) into undoped STO weakens the double Schottky barrier and thereby results in a simultaneous increase in both carrier concentration and mobility of undoped STO. The enhanced mobility exhibits single crystal-like behavior. This increase in the carrier concentration and mobility boosts the electrical conductivity and power factor of undoped STO, which is attributed to the reduction of the double Schottky barrier height and/or the band alignment of STO and RGO that allow the charge transfer through the interface at grain boundaries. Furthermore, this STO/RGO interface also enhances the phonon scattering, which results in low thermal conductivity. This strategy significantly increases the ratio of σ/κ, resulting in an enhancement in ZT as compared with pure undoped STO. This study opens a new window to optimize the TE properties of many candidate materials.
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Affiliation(s)
- Jamil Ur Rahman
- Energy & Environmental Materials Division, Korea Institute of Ceramic Engineering & Technology, Jinju, 52861, South Korea
- School of Materials Science and Engineering, Changwon National University, Changwon, 51140, South Korea
| | - Nguyen Van Du
- Energy & Environmental Materials Division, Korea Institute of Ceramic Engineering & Technology, Jinju, 52861, South Korea
- School of Materials Science and Engineering, Changwon National University, Changwon, 51140, South Korea
| | - Woo Hyun Nam
- Energy & Environmental Materials Division, Korea Institute of Ceramic Engineering & Technology, Jinju, 52861, South Korea
| | - Weon Ho Shin
- Energy & Environmental Materials Division, Korea Institute of Ceramic Engineering & Technology, Jinju, 52861, South Korea
| | - Kyu Hyoung Lee
- Department of Materials Science and Engineering, Yonsei University, Seoul, 03722, South Korea
| | - Won-Seon Seo
- Energy & Environmental Materials Division, Korea Institute of Ceramic Engineering & Technology, Jinju, 52861, South Korea
| | - Myong Ho Kim
- School of Materials Science and Engineering, Changwon National University, Changwon, 51140, South Korea
| | - Soonil Lee
- School of Materials Science and Engineering, Changwon National University, Changwon, 51140, South Korea.
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13
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Thind AS, Luo G, Hachtel JA, Morrell MV, Cho SB, Borisevich AY, Idrobo JC, Xing Y, Mishra R. Atomic Structure and Electrical Activity of Grain Boundaries and Ruddlesden-Popper Faults in Cesium Lead Bromide Perovskite. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1805047. [PMID: 30506822 DOI: 10.1002/adma.201805047] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 11/05/2018] [Indexed: 06/09/2023]
Abstract
To evaluate the role of planar defects in lead-halide perovskites-cheap, versatile semiconducting materials-it is critical to examine their structure, including defects, at the atomic scale and develop a detailed understanding of their impact on electronic properties. In this study, postsynthesis nanocrystal fusion, aberration-corrected scanning transmission electron microscopy, and first-principles calculations are combined to study the nature of different planar defects formed in CsPbBr3 nanocrystals. Two types of prevalent planar defects from atomic resolution imaging are observed: previously unreported Br-rich [001](210)∑5 grain boundaries (GBs) and Ruddlesden-Popper (RP) planar faults. The first-principles calculations reveal that neither of these planar faults induce deep defect levels, but their Br-deficient counterparts do. It is found that the ∑5 GB repels electrons and attracts holes, similar to an n-p-n junction, and the RP planar defects repel both electrons and holes, similar to a semiconductor-insulator-semiconductor junction. Finally, the potential applications of these findings and their implications to understand the planar defects in organic-inorganic lead-halide perovskites that have led to solar cells with extremely high photoconversion efficiencies are discussed.
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Affiliation(s)
- Arashdeep Singh Thind
- Institute of Materials Science & Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Guangfu Luo
- Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Jordan A Hachtel
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Maria V Morrell
- Department of Chemical Engineering, University of Missouri, Columbia, MO, 65211, USA
| | - Sung Beom Cho
- Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Albina Y Borisevich
- Material Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Juan-Carlos Idrobo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Yangchuan Xing
- Department of Chemical Engineering, University of Missouri, Columbia, MO, 65211, USA
| | - Rohan Mishra
- Institute of Materials Science & Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA
- Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, 63130, USA
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14
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Gao P, Yang S, Ishikawa R, Li N, Feng B, Kumamoto A, Shibata N, Yu P, Ikuhara Y. Atomic-Scale Measurement of Flexoelectric Polarization at SrTiO_{3} Dislocations. PHYSICAL REVIEW LETTERS 2018; 120:267601. [PMID: 30004731 DOI: 10.1103/physrevlett.120.267601] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 05/06/2018] [Indexed: 05/27/2023]
Abstract
Owing to the broken translational symmetry at dislocations, a strain gradient naturally exists around the dislocation cores and can significantly influence the electrical and mechanical properties. We use aberration corrected scanning transmission electron microscopy to directly measure the flexoelectric polarization (∼28 μC cm^{-2}) at dislocation cores in SrTiO_{3}. The polarization charges can interact with the nonstoichiometric dislocation cores and thus impact the electrical activities. Our findings can help us to understand the properties of dislocations in perovskite, providing new insights into the design of new devices via defect engineering such as bicrystal fabrication and thin film growth.
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Affiliation(s)
- Peng Gao
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
| | - Shuzhen Yang
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tshinghua University, Beijing 100084, China
| | - Ryo Ishikawa
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - Ning Li
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Bin Feng
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - Akihito Kumamoto
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - Naoya Shibata
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - Pu Yu
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, China
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tshinghua University, Beijing 100084, China
| | - Yuichi Ikuhara
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
- Nanostructures Research Laboratory, Japan Fine Ceramic Center, Nagoya 456-8587, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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15
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Foster ME, Sohlberg K, Allendorf MD, Talin AA. Unraveling the Semiconducting/Metallic Discrepancy in Ni 3(HITP) 2. J Phys Chem Lett 2018; 9:481-486. [PMID: 29316790 DOI: 10.1021/acs.jpclett.7b03140] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 is a π-stacked layered metal-organic framework material with extended π-conjugation that is analogous to graphene. Published experimental results indicate that the material is semiconducting, but all theoretical studies to date predict the bulk material to be metallic. Given that previous experimental work was carried out on specimens containing complex nanocrystalline microstructures and the tendency for internal interfaces to introduce transport barriers, we apply DFT to investigate the influence of internal interface defects on the electronic structure of Ni3(HITP)2. The results show that interface defects can introduce a transport barrier by breaking the π-conjugation and/or decreasing the dispersion of the electronic bands near the Fermi level. We demonstrate that the presence of defects can open a small gap, in the range of 15-200 meV, which is consistent with the experimentally inferred hopping barrier.
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Affiliation(s)
- Michael E Foster
- Sandia National Laboratories , Livermore, California 94551-0969, United States
| | - Karl Sohlberg
- Department of Chemistry, Drexel University , Philadelphia, Pennsylvania 19104, United States
| | - Mark D Allendorf
- Sandia National Laboratories , Livermore, California 94551-0969, United States
| | - A Alec Talin
- Sandia National Laboratories , Livermore, California 94551-0969, United States
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16
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Gao P, Ishikawa R, Feng B, Kumamoto A, Shibata N, Ikuhara Y. Atomic-scale structure relaxation, chemistry and charge distribution of dislocation cores in SrTiO3. Ultramicroscopy 2018; 184:217-224. [DOI: 10.1016/j.ultramic.2017.09.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Revised: 09/14/2017] [Accepted: 09/22/2017] [Indexed: 11/30/2022]
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17
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Song K, Du K, Ye H. Atomic structure and chemistry of a[100] dislocation cores in La 2/3Sr 1/3MnO 3 films. Micron 2017; 96:72-76. [PMID: 28273523 DOI: 10.1016/j.micron.2017.02.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 02/20/2017] [Accepted: 02/20/2017] [Indexed: 10/20/2022]
Abstract
Oxide thin films with perovskite structures possess multifunctional properties, while defects in the films usually have significant influences on their physical properties. Here, the atomic structure and chemistry of a[100] dislocation cores in epitaxial La2/3Sr1/3MnO3 films were investigated by aberration-corrected scanning transmission electron microscopy combining with atomically resolved electron energy-loss spectroscopy imaging. The results demonstrated an edge dislocation terminated with Mn columns and significant nonstoichiometry at the dislocation core region. Quantitative analysis using core-loss spectrum indicates that La/Mn and O/Mn ratios are decreased at the dislocation core. Antisite defects with Mn ions at La-sites were directly determined at the dislocation cores with electron energy-loss spectroscopy. The structure of the dislocation core is discussed on the basis of high-angle annular dark-field imaging and electron energy loss spectroscopy results.
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Affiliation(s)
- Kepeng Song
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
| | - Kui Du
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
| | - Hengqiang Ye
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
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18
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Paving the way to nanoionics: atomic origin of barriers for ionic transport through interfaces. Sci Rep 2015; 5:17229. [PMID: 26673351 PMCID: PMC4682188 DOI: 10.1038/srep17229] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 10/27/2015] [Indexed: 12/03/2022] Open
Abstract
The blocking of ion transport at interfaces strongly limits the performance of electrochemical nanodevices for energy applications. The barrier is believed to arise from space-charge regions generated by mobile ions by analogy to semiconductor junctions. Here we show that something different is at play by studying ion transport in a bicrystal of yttria (9% mol) stabilized zirconia (YSZ), an emblematic oxide ion conductor. Aberration-corrected scanning transmission electron microscopy (STEM) provides structure and composition at atomic resolution, with the sensitivity to directly reveal the oxygen ion profile. We find that Y segregates to the grain boundary at Zr sites, together with a depletion of oxygen that is confined to a small length scale of around 0.5 nm. Contrary to the main thesis of the space-charge model, there exists no evidence of a long-range O vacancy depletion layer. Combining ion transport measurements across a single grain boundary by nanoscale electrochemical strain microscopy (ESM), broadband dielectric spectroscopy measurements, and density functional calculations, we show that grain-boundary-induced electronic states act as acceptors, resulting in a negatively charged core. Besides the possible effect of the modified chemical bonding, this negative charge gives rise to an additional barrier for ion transport at the grain boundary.
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19
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Choi H, Song JD, Lee KR, Kim S. Correlated Visible-Light Absorption and Intrinsic Magnetism of SrTiO3 Due to Oxygen Deficiency: Bulk or Surface Effect? Inorg Chem 2015; 54:3759-65. [DOI: 10.1021/ic502905m] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Heechae Choi
- Center
for Computational Science and ‡Center for Optoelectronics Convergence
System, Korea Institute of Science and Technology, Hwarangro 14 Gil 5, 136-791, Seoul, Korea
| | - Jin Dong Song
- Center
for Computational Science and ‡Center for Optoelectronics Convergence
System, Korea Institute of Science and Technology, Hwarangro 14 Gil 5, 136-791, Seoul, Korea
| | - Kwang-Ryeol Lee
- Center
for Computational Science and ‡Center for Optoelectronics Convergence
System, Korea Institute of Science and Technology, Hwarangro 14 Gil 5, 136-791, Seoul, Korea
| | - Seungchul Kim
- Center
for Computational Science and ‡Center for Optoelectronics Convergence
System, Korea Institute of Science and Technology, Hwarangro 14 Gil 5, 136-791, Seoul, Korea
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20
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Condensation of two-dimensional oxide-interfacial charges into one-dimensional electron chains by the misfit-dislocation strain field. Nat Commun 2014; 5:3522. [DOI: 10.1038/ncomms4522] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Accepted: 02/27/2014] [Indexed: 11/08/2022] Open
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21
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Liu X, Sohlberg K. Theoretical calculations on layered perovskites: implications for photocatalysis. ACTA ACUST UNITED AC 2014. [DOI: 10.1080/2164232x.2014.891950] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Xiang Liu
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA
| | - Karl Sohlberg
- Department of Chemistry, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA
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22
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Liu B, Cooper VR, Xu H, Xiao H, Zhang Y, Weber WJ. Composition dependent intrinsic defect structures in SrTiO3. Phys Chem Chem Phys 2014; 16:15590-6. [DOI: 10.1039/c4cp01510j] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sr/Ti composition dependent intrinsic defect complexes are predicted; providing guidelines for optimizing the functionality of SrTiO3 in experiments.
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Affiliation(s)
- Bin Liu
- Materials Science and Technology Division
- Oak Ridge National Laboratory
- Oak Ridge, USA
| | - Valentino R. Cooper
- Materials Science and Technology Division
- Oak Ridge National Laboratory
- Oak Ridge, USA
| | - Haixuan Xu
- Department of Materials Science and Engineering
- University of Tennessee
- Knoxville, USA
| | - Haiyan Xiao
- Department of Materials Science and Engineering
- University of Tennessee
- Knoxville, USA
| | - Yanwen Zhang
- Materials Science and Technology Division
- Oak Ridge National Laboratory
- Oak Ridge, USA
- Department of Materials Science and Engineering
- University of Tennessee
| | - William J. Weber
- Materials Science and Technology Division
- Oak Ridge National Laboratory
- Oak Ridge, USA
- Department of Materials Science and Engineering
- University of Tennessee
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23
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Polfus JM, Toyoura K, Oba F, Tanaka I, Haugsrud R. Defect chemistry of a BaZrO3 Σ3 (111) grain boundary by first principles calculations and space-charge theory. Phys Chem Chem Phys 2012; 14:12339-46. [PMID: 22864195 DOI: 10.1039/c2cp41101f] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Defect calculations from density functional theory are implemented with space-charge theory models to describe the equilibrium defect chemistry of a Σ3 (111) symmetric tilt boundary in BaZrO(3). As such, the space-charge potential and the concentrations of , , , NH and in the bulk, core and space-charge regions of the interface are calculated as a function of temperature and atmospheric conditions. Our results show that the core will be predominated by under hydrating conditions and that the space-charge potential increases with water vapor pressure. Under nitriding conditions, , NH and will predominate the core in different temperature regimes and effects of these defects on the space-charge properties are discussed.
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Affiliation(s)
- Jonathan M Polfus
- Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalléen 21, NO-0349 Oslo, Norway
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24
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Lee WM, Sung JH, Chu K, Moya X, Lee D, Kim CJ, Mathur ND, Cheong SW, Yang CH, Jo MH. Spatially resolved photodetection in leaky ferroelectric BiFeO(3). ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2012; 24:OP49-OP53. [PMID: 22282134 DOI: 10.1002/adma.201102816] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Indexed: 05/31/2023]
Abstract
Potential gradients due to the spontaneous polarization of BiFeO(3) yield asymmetric and nonlinear photocarrier dynamics. Photocurrent direction is determined by local ferroelectric domain orientation, whereas magnitude is spectrally centered around charged domain walls that are associated with oxygen vacancy migration. Photodetection can be electrically controlled by manipulating ferroelectric domain configurations.
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Affiliation(s)
- Won-Mo Lee
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Gyungbuk, Korea
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25
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The Application of Scanning Transmission Electron Microscopy (STEM) to the Study of Nanoscale Systems. MODELING NANOSCALE IMAGING IN ELECTRON MICROSCOPY 2012. [DOI: 10.1007/978-1-4614-2191-7_2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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26
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Lee HS, Findlay SD, Mizoguchi T, Ikuhara Y. The effect of vacancies on the annular dark field image contrast of grain boundaries: A SrTiO3 case study. Ultramicroscopy 2011; 111:1531-9. [DOI: 10.1016/j.ultramic.2011.08.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 08/24/2011] [Accepted: 08/25/2011] [Indexed: 11/16/2022]
Affiliation(s)
- H-S Lee
- Institute of Engineering Innovation, The University of Tokyo, Tokyo 116-0013, Japan
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27
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Ávila-Brande D, Boese M, Houben L, Schubert J, Luysberg M. Strain-induce shift of the crystal-field splitting of SrTiO₃ embedded in scandate multilayers. ACS APPLIED MATERIALS & INTERFACES 2011; 3:1545-1551. [PMID: 21462998 DOI: 10.1021/am200115j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Strained SrTiO₃ layers have become of interest, since the paraelectric-to-ferroelectric transition temperature can be increased to room temperature. A linear relationship between strain and energy splitting of the fundamental transitions in the fine structure of Ti L(₂,₃) and O K edges is observed, that can be exploited to measure strain from electronic transitions, complementary to measuring local strain directly via high-resolution transmission electron microscopy (HRTEM) images. In particular, for both methods, the geometrical phase analysis performed on high-resolution images and the measurement of the energy splitting by energy loss spectroscopy, tensile strain of SrTiO₃ layers was measured when grown on DyScO₃ and GdScO₃ substrates. The effect of strain on the electron loss near edge structure (ELNES) of the Ti L(₂,₃) edge in comparison to unstrained samples is analyzed. Ab initio calculations of the Ti L(₂,₃) and O K edge show a linear variation of the crystal field splitting with strain. Calculated and experimental values of the crystal field splitting show a very good agreement.
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Affiliation(s)
- D Ávila-Brande
- Ernst Ruska-Centre and Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich, Germany.
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28
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Pennycook S, Lupini AR, Varela M, Borisevich A, Chisholm MF, Abe E, Dellby N, Krivanek O, Nellist PD, Wang LG, Buczko R, Fan X, Pantelides ST. Nanoscale Structure/Property Correlation Through Aberration-Corrected Stem And Theory. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-738-g1.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The combination of atomic-resolution Z-contrast microscopy, electron energy loss spectroscopy and first-principles theory has proved to be a powerful means for structure property correlations at interfaces and nanostructures. The scanning transmission electron microscope (STEM) now routinely provides atomic-sized electron beams, allowing simultaneous Z-contrast imaging and EELS as shown in Fig. 1. The feasiblity of correcting the inherently large spherical aberration of microscope objective lenses promises to at least double the achievable resolution. The potential benefits for the STEM, however, may turn out to be much greater than those for the conventional TEM because it is very much less sensitive to chromatic instabilities. The 100 kV VG Microscopes HB501UX at Oak Ridge National Laboratory (ORNL) is now fitted with an aberration corrector constructed by Nion Co., which improved its resolution from 2.2 Å (full-width-half-maximum probe intensity) to around 1.3 Å. It is now very comparable in performance to the uncorrected 300 kV HB603U STEM at ORNL which, before correction, also had a directly interpretable resolution of 1.3 Å, although information transfer had been demonstrated down to 0.78 Å8. Initial results after installing an aberration corrector on the 300 kV STEM indicate a resolution of 0.84 Å. The theoretically achievable probe size in the absence of instabilities is predicted to be 0.5 Å.
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29
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Hojo H, Mizoguchi T, Ohta H, Findlay SD, Shibata N, Yamamoto T, Ikuhara Y. Atomic structure of a CeO2 grain boundary: the role of oxygen vacancies. NANO LETTERS 2010; 10:4668-4672. [PMID: 20977250 DOI: 10.1021/nl1029336] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Determining both cation and oxygen sublattices of grain boundaries is essential to understand the properties of oxides. Here, with scanning transmission electron microscopy, electron energy-loss spectroscopy, and first-principles calculations, both the Ce and oxygen sublattices of a (210)Σ5 CeO(2) grain boundary were determined. Oxygen vacancies are shown to play a crucial role in the stable grain boundary structure. This finding paves the way for a comprehensive understanding of grain boundaries through the atomic scale determination of atom and defect locations.
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Affiliation(s)
- Hajime Hojo
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
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30
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Arredondo M, Ramasse QM, Weyland M, Mahjoub R, Vrejoiu I, Hesse D, Browning ND, Alexe M, Munroe P, Nagarajan V. Direct evidence for cation non-stoichiometry and cottrell atmospheres around dislocation cores in functional oxide interfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2010; 22:2430-4. [PMID: 20432474 DOI: 10.1002/adma.200903631] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
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31
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Hafemeister M, Siebentritt S, Albert J, Lux-Steiner MC, Sadewasser S. Large neutral barrier at grain boundaries in chalcopyrite thin films. PHYSICAL REVIEW LETTERS 2010; 104:196602. [PMID: 20866985 DOI: 10.1103/physrevlett.104.196602] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Indexed: 05/29/2023]
Abstract
The electronic structure of grain boundaries in polycrystalline Cu(In,Ga)Se2 thin films and their role on solar cell device efficiency is currently under intense investigation. A neutral barrier of about 0.5 eV has been suggested as the reason for the benign behavior of grain boundaries in chalcopyrites. Previous experimental investigations have in fact shown a neutral barrier but only a few 10 meV high, which cannot be expected to have a significant influence on the solar cell efficiency. Here we show that a full investigation of the electrical behavior of charged and neutral grain boundaries shows the existence of an additional narrow neutral barrier, several 100 meV high, which is tunneled through by the majority carriers but is sufficiently high to explain the benign behavior of the grain boundaries.
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Affiliation(s)
- Michael Hafemeister
- Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
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32
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Haruta M, Komatsu H, Kurata H, Shimakawa Y, Isoda S. HAADF-STEM analysis of layered double perovskite La(2)CuSnO(6) grown epitaxially. J Microsc 2009; 236:100-3. [PMID: 19903232 DOI: 10.1111/j.1365-2818.2009.03235.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Structural observation of layered double perovskite oxide La(2)CuSnO(6) thin films grown epitaxially on SrTiO(3) is reported by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Particularly the transition layer at the interface was observed, and the first B site layer at the interface was found to be almost formed by the Cu atomic layer as the random structure, followed by formation of the layered structure. In addition, HAADF-STEM images indicate that the thin film is not single crystalline, but some irregular structures were observed to grow around the interface near atomic steps of the substrate of SrTiO(3). Therefore, the steps largely affect the growth process of the thin film.
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Affiliation(s)
- M Haruta
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
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33
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Pennycook SJ, Varela M, Lupini AR, Oxley MP, Chisholm MF. Atomic-resolution spectroscopic imaging: past, present and future. JOURNAL OF ELECTRON MICROSCOPY 2009; 58:87-97. [PMID: 19158206 DOI: 10.1093/jmicro/dfn030] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
This review examines the development of atomically resolved electron energy loss spectroscopy from the first demonstration of plane-by-plane compositional profiling, through column-by-column spectroscopy to full two-dimensional and potentially three-dimensional spectroscopic imaging. Examples will be presented to highlight the increasing analytical sensitivity and image contrast obtained through each generation of aberration correction, moving towards the ultimate goal of mapping electronic structure inside materials with atomic resolution.
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Affiliation(s)
- Stephen J Pennycook
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6030, USA.
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34
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De Souza RA. The formation of equilibrium space-charge zones at grain boundaries in the perovskite oxide SrTiO3. Phys Chem Chem Phys 2009; 11:9939-69. [DOI: 10.1039/b904100a] [Citation(s) in RCA: 170] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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35
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Sang X, Du K, Zhuo M, Ye H. On the accuracy of maximum entropy reconstruction of high-resolution Z-contrast STEM images. Micron 2008; 40:247-54. [PMID: 18774301 DOI: 10.1016/j.micron.2008.07.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Revised: 07/24/2008] [Accepted: 07/26/2008] [Indexed: 10/21/2022]
Abstract
The accuracy of maximum entropy reconstruction of Z-contrast STEM images has been evaluated with the effects of experimental variables and noise taken into account by the means of image simulation. As the specimen contains atom species of greatly different atomic numbers, special attention is given to the reliability of the position and composition of lighter atoms that are determined from Z-contrast images in the presence of heavier atoms. When the noise is moderate (SNR >2.5), the position of atom columns can be measured within an accuracy of 0.03 nm. With a higher signal-to-noise ratio (SNR >5) the composition of lighter atoms can be resolved reliably from the Z-contrast images. However, when image noise increases, the relative intensity of lighter atoms may deviate from the actual value in the specimen object function.
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Affiliation(s)
- Xiahan Sang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 110016 Shenyang, China
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36
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Klie RF, Zhao Y, Yang G, Zhu Y. High-resolution Z-contrast imaging and EELS study of functional oxide materials. Micron 2008; 39:723-33. [DOI: 10.1016/j.micron.2007.10.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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37
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Pennycook SJ. Investigating the optical properties of dislocations by scanning transmission electron microscopy. SCANNING 2008; 30:287-298. [PMID: 18613065 DOI: 10.1002/sca.20114] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The scanning transmission electron microscope (STEM) allows collection of a number of simultaneous signals, such as cathodoluminescence (CL), transmitted electron intensity and spectroscopic information from individual localized defects. This review traces the development of CL and atomic resolution imaging from their early inception through to the possibilities that exist today for achieving a true atomic-scale understanding of the optical properties of individual dislocations cores. This review is dedicated to Professor David Holt, a pioneer in this field.
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Affiliation(s)
- S J Pennycook
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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38
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Klie RF, Johnson C, Zhu Y. Atomic-resolution STEM in the aberration-corrected JEOL JEM2200FS. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2008; 14:104-112. [PMID: 18171499 DOI: 10.1017/s1431927608080136] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2007] [Accepted: 08/07/2007] [Indexed: 05/25/2023]
Abstract
We report on the performance of our aberration-corrected JEOL-JEM2200FS electron microscope. This high-resolution field-mission TEM/STEM is equipped with a Schottky field-emission gun operated at 200 kV, a CEOS probe corrector, and an in-column energy filter. We focus on the performance of the probe corrector and show that the Si [110] dumbbell structure can be routinely resolved in STEM mode with the power spectrum indicating a probe size of approximately 1 A. Ronchigram analysis suggests that the constant phase area is extended from 15 mrad to 35 mrad after corrector tuning. We also report the performance of our newly installed JEOL-JEM2200MCO, an upgraded version of the JEM2200FS, equipped with two CEOS aberration correctors (and a monochromator), one for the probe-forming lens and the other for the postspecimen objective lens. Based on Young's fringe analysis of Au particles on amorphous Ge, initial results show that the information limit in TEM mode with the aberration correction (Cs = -3.8 microm) is approximately 0.12 nm. Materials research applications using these two instruments are described including atomic-column-resolved Z-contrast imaging and electron energy-loss spectroscopy of oxide hetero-interfaces and strain mapping of a SrTiO3 tilt-grain boundary. The requirements for a high-precision TEM laboratory to house an aberration-corrected microscope are also discussed.
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Affiliation(s)
- Robert F Klie
- Institute for Advanced Electron Microscopy, Brookhaven National Laboratory, Upton, NY 11973, USA.
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39
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Pennycook S, Chisholm M, Lupini A, Varela M, van Benthem K, Borisevich A, Oxley M, Luo W, Pantelides S. Chapter 9 Materials Applications of Aberration-Corrected Scanning Transmission Electron Microscopy. ADVANCES IN IMAGING AND ELECTRON PHYSICS 2008. [DOI: 10.1016/s1076-5670(08)01009-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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40
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Fitting L, Thiel S, Schmehl A, Mannhart J, Muller DA. Subtleties in ADF imaging and spatially resolved EELS: A case study of low-angle twist boundaries in SrTiO3. Ultramicroscopy 2006; 106:1053-61. [PMID: 16867311 DOI: 10.1016/j.ultramic.2006.04.019] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2005] [Revised: 11/02/2005] [Accepted: 04/06/2006] [Indexed: 10/24/2022]
Abstract
A screw dislocation network at the low-angle SrTiO3/Nb:SrTiO3 twist grain boundary has been analyzed by annular dark field (ADF) imaging and spatially resolved electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). The cores of one set of dislocations running parallel to the beam direction appear dark in the ADF STEM images. EELS on the dislocation core reveals a reduced Sr/Ti ratio compared to the bulk suggesting Sr-deficient cores. The second set of dislocations, orthogonal to the latter, is imaged by its strain field using low-angle annular dark field (LAADF) imaging. Multislice image simulations suggest channeling of the electron probe on the atomic columns for small tilts, theta < 1 degree, where the Sr columns act as beam guides. Only for larger tilts is the channeling effect strongly reduced and the fringe contrast approaches the value predicted by a purely incoherent imaging model. Ti-L(2,3) EELS across the dislocation core shows an asymmetry between the EELS and the ADF signal which cannot be explained by the geometry or beam broadening. This asymmetry might be explained by an effective nonlocal potential representing inelastic scattering in EELS.
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Affiliation(s)
- L Fitting
- Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
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41
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Szot K, Speier W, Bihlmayer G, Waser R. Switching the electrical resistance of individual dislocations in single-crystalline SrTiO3. NATURE MATERIALS 2006; 5:312-20. [PMID: 16565712 DOI: 10.1038/nmat1614] [Citation(s) in RCA: 395] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Accepted: 02/02/2006] [Indexed: 05/03/2023]
Abstract
The great variability in the electrical properties of multinary oxide materials, ranging from insulating, through semiconducting to metallic behaviour, has given rise to the idea of modulating the electronic properties on a nanometre scale for high-density electronic memory devices. A particularly promising aspect seems to be the ability of perovskites to provide bistable switching of the conductance between non-metallic and metallic behaviour by the application of an appropriate electric field. Here we demonstrate that the switching behaviour is an intrinsic feature of naturally occurring dislocations in single crystals of a prototypical ternary oxide, SrTiO(3). The phenomenon is shown to originate from local modulations of the oxygen content and to be related to the self-doping capability of the early transition metal oxides. Our results show that extended defects, such as dislocations, can act as bistable nanowires and hold technological promise for terabit memory devices.
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Affiliation(s)
- Krzysztof Szot
- Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich, Germany
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Shao R, Chisholm MF, Duscher G, Bonnell DA. Low-temperature resistance anomaly at SrTiO3 grain boundaries: evidence for an interface-induced phase transition. PHYSICAL REVIEW LETTERS 2005; 95:197601. [PMID: 16384023 DOI: 10.1103/physrevlett.95.197601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2005] [Indexed: 05/05/2023]
Abstract
Variable temperature transport between 1.4 and 300 K, structural imaging, and theoretical calculations were used to characterize the properties of electrically active 24 degrees and 36.8 degrees [001] tilt SrTiO3 grain boundaries with 0.1 at. % niobium doping. An anomaly in boundary resistance and capacitance characteristics typical of a positive temperature coefficient effect is observed. This behavior is indicative of interface-induced dipole ordering. The detailed atomic structures of these grain boundaries were determined from a comparison of ab initio calculations and Z-contrast TEM images. The number of excess electrons at the boundaries determined experimentally and theoretically agrees and is associated with the boundary structural units.
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Affiliation(s)
- Rui Shao
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Klie RF, Buban JP, Varela M, Franceschetti A, Jooss C, Zhu Y, Browning ND, Pantelides ST, Pennycook SJ. Enhanced current transport at grain boundaries in high-T(c) superconductors. Nature 2005; 435:475-8. [PMID: 15917804 DOI: 10.1038/nature03644] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Accepted: 04/14/2005] [Indexed: 11/08/2022]
Abstract
Large-scale applications of high-transition-temperature (high-T(c)) superconductors, such as their use in superconducting cables, are impeded by the fact that polycrystalline materials (the only practical option) support significantly lower current densities than single crystals. The superconducting critical current density (J(c)) across a grain boundary drops exponentially if the misorientation angle exceeds 2 degrees -7 degrees. Grain texturing reduces the average misorientation angle, but problems persist. Adding impurities (such as Ca in YBa2Cu3O7-delta; YBCO) leads to increased J(c) (refs 9, 10), which is generally attributed to excess holes introduced by Ca2+ substituting for Y3+ (ref. 11). However, a comprehensive physical model for the role of grain boundaries and Ca doping has remained elusive. Here we report calculations, imaging and spectroscopy at the atomic scale that demonstrate that in poly-crystalline YBCO, highly strained grain-boundary regions contain excess O vacancies, which reduce the local hole concentration. The Ca impurities indeed substitute for Y, but in grain-boundary regions under compression and tension they also replace Ba and Cu, relieving strain and suppressing O-vacancy formation. Our results demonstrate that the ionic radii are more important than their electronic valences for enhancing J(c).
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Affiliation(s)
- R F Klie
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA.
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44
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Abstract
Atomic resolution scanning transmission electron microscopy (STEM) analysis, in particular the combination of Z-contrast imaging and electron energy-loss spectroscopy (EELS) has been successfully used to measure the atomic and electronic structure of materials with sub-nanometer spatial resolution. Furthermore, the combination of this incoherent imaging technique with EELS allows us to correlate certain structural features, such as defects or interfaces directly with the measured changes in the local electronic fine-structure. In this review, we will discuss the experimental procedures for achieving high-resolution Z-contrast imaging and EELS. We will describe the alignment and experimental setup for high-resolution STEM analysis and also describe some of our recent results where the combined use of atomic-resolution Z-contrast imaging and column-by-column EELS has helped solve important materials science problems.
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Affiliation(s)
- R F Klie
- Brookhaven National Laboratory, Center for Functional Nanomaterials, 76 Cornell Ave., Upton, NY 11973, USA.
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Lupini AR, Chisholm MF, van Benthem K, Allen LJ, Oxley MP, Findlay SD, Varela M, Pennycook SJ. Limitations to the measurement of oxygen concentrations by HRTEM imposed by surface roughness. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2005; 11:111-115. [PMID: 15817138 DOI: 10.1017/s1431927605210309] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In an article published inMicroscopy and Microanalysisrecently (Jia et al., 2004), it was claimed that aberration-corrected high resolution transmission electron microscopy (HRTEM) allows the quantitative measurement of oxygen concentrations in ceramic materials with atomic resolution. Similar claims have recently appeared elsewhere, based on images obtained through aberration correction (Jia et al., 2003; Jia & Urban, 2004) or very high voltages (Zhang et al., 2003). Seeing oxygen columns is a significant achievement of great importance (Spence, 2003) that will doubtlessly allow some exciting new science; however, other models could provide a better explanation for some of the experimental data than variations in the oxygen concentration. Quantification of the oxygen concentrations was attempted by comparing experimental images with simulations in which the fractional occupancy in individual oxygen columns was reduced. The results were interpreted as representing nonstoichiometry within the bulk and at grain boundaries. This is plausible because previous studies have shown that grain boundaries can be nonstoichiometric (Kim et al., 2001), and it is indeed possible that oxygen vacancies are present at boundaries or in the bulk.However, is this the only possible interpretation?We show that for the thicknesses considered a better match to the images is obtained using a simple model of surface damage in which atoms are removed from the surface, which would usually be interpreted as surface damage or local thickness variation (from ion milling, for example).
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46
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Gemming S, Schreiber M. Impurity and vacancy clustering at the Σ3(111)[1−10] grain boundary in strontium titanate. Chem Phys 2005. [DOI: 10.1016/j.chemphys.2004.02.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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47
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Abstract
Using high-resolution imaging at negative spherical aberration of the objective lens in an aberration-corrected transmission electron microscope, we measure the concentration of oxygen in Sigma3[111] twin boundaries in BaTiO3 thin films at atomic resolution. On average, 68% of the boundary oxygen sites are occupied, and the others are left vacant. The modified Ti2O9 group unit thus formed reduces the grain boundary energy and provides a way of accommodating oxygen vacancies occurring in oxygen-deficient material by the formation of a nanotwin lamellae structure. The atomically resolved measurement technique offers the potential for studies on oxide materials in which the electronic properties sensitively depend on the local oxygen content.
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Affiliation(s)
- C L Jia
- Institute for Solid State Research, Research Center Jülich, D-52425 Jülich, Germany
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48
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Varela M, Findlay SD, Lupini AR, Christen HM, Borisevich AY, Dellby N, Krivanek OL, Nellist PD, Oxley MP, Allen LJ, Pennycook SJ. Spectroscopic imaging of single atoms within a bulk solid. PHYSICAL REVIEW LETTERS 2004; 92:095502. [PMID: 15089484 DOI: 10.1103/physrevlett.92.095502] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2003] [Indexed: 05/24/2023]
Abstract
The ability to localize, identify, and measure the electronic environment of individual atoms will provide fundamental insights into many issues in materials science, physics, and nanotechnology. We demonstrate, using an aberration-corrected scanning transmission electron microscope, the spectroscopic imaging of single La atoms inside CaTiO3. Dynamical simulations confirm that the spectroscopic information is spatially confined around the scattering atom. Furthermore, we show how the depth of the atom within the crystal may be estimated.
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Affiliation(s)
- M Varela
- Condensed Matter Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6030, USA
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Recent Developments in the Microscopy of Ceramics. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/s1076-5670(04)32004-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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50
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Pennycook SJ, Lupini AR, Kadavanich A, MeBride JR, Rosenthal SJ, Puetter RC, Yahil A, Krivanek OL, Dellby N, Nellist PDL, Duscher G, Wang LG, Pantelides ST. Aberration-Corrected Scanning Transmission Electron Microscopy: The Potential for Nano- and Interface Science. ACTA ACUST UNITED AC 2003. [DOI: 10.3139/146.030350] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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