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Gao Z, Leng C, Zhao H, Wei X, Shi H, Xiao Z. The Electrical Behaviors of Grain Boundaries in Polycrystalline Optoelectronic Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2304855. [PMID: 37572037 DOI: 10.1002/adma.202304855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 07/18/2023] [Indexed: 08/14/2023]
Abstract
Polycrystalline optoelectronic materials are widely used for photoelectric signal conversion and energy harvesting and play an irreplaceable role in the semiconductor field. As an important factor in determining the optoelectronic properties of polycrystalline materials, grain boundaries (GBs) are the focus of research. Particular emphases are placed on the generation and height of GB barriers, how carriers move at GBs, whether GBs act as carrier transport channels or recombination sites, and how to change the device performance by altering the electrical behaviors of GBs. This review introduces the evolution of GB theory and experimental observation history, classifies GB electrical behaviors from the perspective of carrier dynamics, and summarizes carrier transport state under external conditions such as bias and illumination and the related band bending. Then the carrier scattering at GBs and the electrical differences between GBs and twin boundaries are discussed. Last, the review describes how the electrical behaviors of GBs can be influenced and modified by treatments such as passivation or by consciously adjusting the distribution of grain boundary elements. By studying the carrier dynamics and the relevant electrical behaviors of GBs in polycrystalline materials, researchers can develop optoelectronics with higher performance.
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Affiliation(s)
- Zheng Gao
- Research Center for Quantum Information, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China
- Research Center for Nanofabrication and System Integration, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
- Chongqing School, University of Chinese Academy of Sciences, Chongqing, 400714, China
| | - Chongqian Leng
- Research Center for Nanofabrication and System Integration, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
- Chongqing School, University of Chinese Academy of Sciences, Chongqing, 400714, China
| | - Hongquan Zhao
- Research Center for Quantum Information, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
- Chongqing School, University of Chinese Academy of Sciences, Chongqing, 400714, China
| | - Xingzhan Wei
- Research Center for Nanofabrication and System Integration, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
- Chongqing School, University of Chinese Academy of Sciences, Chongqing, 400714, China
| | - Haofei Shi
- Research Center for Nanofabrication and System Integration, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
- Chongqing School, University of Chinese Academy of Sciences, Chongqing, 400714, China
| | - Zeyun Xiao
- Research Center for Quantum Information, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
- Chongqing School, University of Chinese Academy of Sciences, Chongqing, 400714, China
- Research Center for Thin Film Solar Cells, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 400714, China
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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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Wu M, Zhang X, Li X, Qu K, Sun Y, Han B, Zhu R, Gao X, Zhang J, Liu K, Bai X, Li XZ, Gao P. Engineering of atomic-scale flexoelectricity at grain boundaries. Nat Commun 2022; 13:216. [PMID: 35017521 PMCID: PMC8752668 DOI: 10.1038/s41467-021-27906-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 12/17/2021] [Indexed: 12/05/2022] Open
Abstract
Flexoelectricity is a type of ubiquitous and prominent electromechanical coupling, pertaining to the electrical polarization response to mechanical strain gradients that is not restricted by the symmetry of materials. However, large elastic deformation is usually difficult to achieve in most solids, and the strain gradient at minuscule is challenging to control. Here, we exploit the exotic structural inhomogeneity of grain boundary to achieve a huge strain gradient (~1.2 nm-1) within 3-4-unit cells, and thus obtain atomic-scale flexoelectric polarization of up to ~38 μC cm-2 at a 24° LaAlO3 grain boundary. Accompanied by the generation of the nanoscale flexoelectricity, the electronic structures of grain boundaries also become different. Hence, the flexoelectric effect at grain boundaries is essential to understand the electrical activities of oxide ceramics. We further demonstrate that for different materials, altering the misorientation angles of grain boundaries enables tunable strain gradients at the atomic scale. The engineering of grain boundaries thus provides a general and feasible pathway to achieve tunable flexoelectricity.
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Affiliation(s)
- Mei Wu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, 100871, China
| | - Xiaowei Zhang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
| | - Xiaomei Li
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Ke Qu
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, 100871, China
| | - Yuanwei Sun
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, 100871, China
| | - Bo Han
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, 100871, China
| | - Ruixue Zhu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, 100871, China
| | - Xiaoyue Gao
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, 100871, China
| | - Jingmin Zhang
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, 100871, China
| | - Kaihui Liu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing, 100871, China
- Collaborative Innovation Centre 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
| | - Xuedong Bai
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Xin-Zheng Li
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing, 100871, China.
- Collaborative Innovation Centre of Quantum Matter, Beijing, 100871, China.
- Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing, 100871, China.
- Peking University Yangtze Delta Institute of Optoelectronics, Nantong, 226010, Jiangsu, China.
| | - Peng Gao
- 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 Centre 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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Xing W, Zhang Y, Cui J, Liang S, Meng F, Zhu J, Yu R. Atomic structures of twin boundaries in CoO. Phys Chem Chem Phys 2021; 23:25590-25596. [PMID: 34783799 DOI: 10.1039/d1cp04112f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The twinning plane of crystals with a face-centered-cubic (FCC) structure is usually the (111) plane, as found in FCC metals and oxides with FCC sublattices of oxygen, like rock-salt-type NiO and spinel-type Fe3O4. Surprisingly, we found in this work that the twinning plane of rock-salt-type CoO is the (112) plane, although Co is adjacent to Ni in the periodic table. The atomic and electronic structures of the CoO(112) twin boundary with in-plane shift vector 1/2[111] have been studied combining aberration-corrected scanning transmission electron microscopy (STEM), electron-energy-loss spectroscopy (EELS), and density functional theory (DFT) calculations. It was found that the atoms at the twin boundary have nominal oxidation states, and the twin boundary remains insulating and antiferromagnetically coupled. Importantly, through the electronic structures and the crystal orbital Hamilton population (COHP) analyses, the (112) twin boundary is found to be more stable than the (111) twin boundary.
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Affiliation(s)
- Wandong Xing
- National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Key Laboratory of Advanced Materials of Ministry of Education of China, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China.
| | - Yang Zhang
- National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Key Laboratory of Advanced Materials of Ministry of Education of China, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China.
| | - Jizhe Cui
- National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Key Laboratory of Advanced Materials of Ministry of Education of China, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China.
| | - Shiyou Liang
- National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Key Laboratory of Advanced Materials of Ministry of Education of China, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China.
| | - Fanyan Meng
- Department of Physics, University of Science and Technology Beijing, Beijing 100083, China.
| | - Jing Zhu
- National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Key Laboratory of Advanced Materials of Ministry of Education of China, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China.
| | - Rong Yu
- National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Key Laboratory of Advanced Materials of Ministry of Education of China, State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China.
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Yun H, Topsakal M, Prakash A, Jalan B, Jeong JS, Birol T, Mkhoyan KA. Metallic line defect in wide-bandgap transparent perovskite BaSnO 3. SCIENCE ADVANCES 2021; 7:7/3/eabd4449. [PMID: 33523903 PMCID: PMC7810381 DOI: 10.1126/sciadv.abd4449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Accepted: 11/24/2020] [Indexed: 06/12/2023]
Abstract
A line defect with metallic characteristics has been found in optically transparent BaSnO3 perovskite thin films. The distinct atomic structure of the defect core, composed of Sn and O atoms, was visualized by atomic-resolution scanning transmission electron microscopy (STEM). When doped with La, dopants that replace Ba atoms preferentially segregate to specific crystallographic sites adjacent to the line defect. The electronic structure of the line defect probed in STEM with electron energy-loss spectroscopy was supported by ab initio theory, which indicates the presence of Fermi level-crossing electronic bands that originate from defect core atoms. These metallic line defects also act as electron sinks attracting additional negative charges in these wide-bandgap BaSnO3 films.
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Affiliation(s)
- Hwanhui Yun
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Mehmet Topsakal
- Nuclear Science and Technology Department, Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Abhinav Prakash
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Bharat Jalan
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jong Seok Jeong
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
- Analytical Sciences Center, LG Chem Ltd., Daejeon, Republic of Korea
| | - Turan Birol
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - K Andre Mkhoyan
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA.
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Affiliation(s)
- Yuichi Ikuhara
- Institute of Engineering Innovation, The University of Tokyo, Japan
- Nanostructure Research Laboratory, Japan Fine Ceramics Center, Japan
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7
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Comparative Study on AC Susceptibility of YBa2Cu3O7−δ Added with BaZrO3 Nanoparticles Prepared via Solid-State and Co-Precipitation Method. CRYSTALS 2019. [DOI: 10.3390/cryst9120655] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Polycrystalline samples of YBa2Cu3O7−δ (Y-123) added with x mol% of BaZrO3 (BZO) nanoparticles (x = 0.0, 2.0, 5.0, and 7.0) were synthesized using co-precipitation (COP) and solid-state (SS) method. X-ray diffraction (XRD) patterns showed the formation of Y-123 and Y-211 as the major and minor phases, respectively. The samples prepared using COP method showed higher weight percentage of Y-123 phase (≤98%) compared to the SS samples (≤93%). A peak corresponding to BZO was also found in the samples added with BZO nanoparticles. The increasing intensity of the BZO peak as the BZO amount increased showed the increasing amount of the unreacted nanoparticles in the samples. Refinement of unit cell lattice parameters indicated that all the samples have an orthorhombic crystal structure and there is no orthorhombic-tetragonal phase transformation. As observed using scanning electron microscopy (SEM), all the samples showed randomly distributed grains with irregular shape. The average grain size for the pure sample prepared using COP method is smaller (0.30 µm) compared with that of the pure SS sample (1.24 µm). Addition of 7.0 mol% BZO led to an increase of average grain size to 0.50 μm and 2.71 μm for the COP and SS samples, respectively, indicating grain growth. AC susceptibility (ACS) measurement showed a decrease in the onset critical temperature, Tc-onset with BZO addition. Comparatively, Tc-onset for the COP samples is higher than that of the SS samples. The value of Josephson’s current, Io increased up to 2.0 mol% BZO addition, above which the Io decreased more drastically for the SS samples. The value of Io is 53.95 μA and 32.08 μA for the 2.0 mol% BZO added SS and COP samples, respectively. The decrease of Io is attributed to the distribution of BZO particles at the grain boundaries as also reflected in the drastic decrease of phase lock-in temperature, Tcj. As a result of smaller average grain size, the presence of more grain boundaries containing insulating BZO particles led to lower Io in the COP samples.
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Fête A, Senatore C. Strong improvement of the transport characteristics of YBa 2Cu 3O 7-x grain boundaries using ionic liquid gating. Sci Rep 2018; 8:17703. [PMID: 30531930 PMCID: PMC6286366 DOI: 10.1038/s41598-018-36166-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 11/13/2018] [Indexed: 11/18/2022] Open
Abstract
For more than 30 years, the remarkable superconducting properties of REBa2Cu3O7-x (RE = rare earth) compounds have triggered research studies across the world. Accordingly, significant progresses have been made both from a basic understanding and a fabrication processes perspective. Yet, today, the major technological bottleneck towards the spread of their practical uses remains the exponential decay of their critical current with grain misorientation in polycrystalline samples. In this work, we used an ionic liquid to apply extremely high transverse electric fields to YBa2Cu3O7-x thin films containing a single well-defined low-angle grain boundary. Our study shows that this technique is very effective to tune the IV characteristics of these weak-links. In-magnetic field measurements allow us to discuss the type of the vortices present at the grain boundary and to unveil a large variation of the local depairing current density with gating. Comparing our results with the ones obtained on chemically-doped grain boundaries, we discuss routes to evaluate the role of local strain in the loss of transparency at cuprates low-angle grain boundaries. In short, this study offers a new opportunity to discuss scenarios leading to the reduced transport capabilities of grain boundaries in cuprates.
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Affiliation(s)
- A Fête
- Department of Quantum Matter Physics (DQMP), University of Geneva, Geneva, Switzerland.
| | - C Senatore
- Department of Quantum Matter Physics (DQMP), University of Geneva, Geneva, Switzerland
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Superdislocations and point defects in pyrochlore Yb 2Ti 2O 7 single crystals and implication on magnetic ground states. Sci Rep 2018; 8:17202. [PMID: 30464180 PMCID: PMC6249211 DOI: 10.1038/s41598-018-35283-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 10/24/2018] [Indexed: 11/08/2022] Open
Abstract
This study reports atomic-scale characterization of structural defects in Yb2Ti2O7, a pyrochlore oxide whose subtle magnetic interactions is prone to small perturbations. Due to discrepancies in the reported magnetic ground states, it has become a pressing issue to determine the nature of defects in this system. In the present study, we use atomic resolution scanning transmission electron microscopy techniques to identify the type of defects in the ytterbium titanate single crystals grown by the conventional optical floating zone (FZ) method. In addition to the known point defects of substitution Yb on Ti B-sites, extended defects such as dissociated superdislocations and anti-phase boundaries were discovered for the first time in this material. Such defects were prevalently observed in the FZ grown single crystals (of a darker color), in contrast to the stoichiometric white polycrystalline powders or high quality colorless single crystals grown by the traveling solvent floating zone technique. The lattice strains from these extended defects result in distortions of Yb-tetrahedron. A change of Ti valance was not detected at the defects. Our findings provide new insights into understanding the nature of defects that are of great importance for the physical property studies of geometrically frustrated compounds. Furthermore, this work sheds light on the complicated core structure of superdislocations that have large Burgers vectors in oxides with complex unit cells.
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Effect of Ag incorporation on structural and opto-electric properties of pyrolized CdO thin films. INTERNATIONAL NANO LETTERS 2018. [DOI: 10.1007/s40089-018-0251-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Yamashita S, Kikkawa J, Yanagisawa K, Nagai T, Ishizuka K, Kimoto K. Atomic number dependence of Z contrast in scanning transmission electron microscopy. Sci Rep 2018; 8:12325. [PMID: 30120323 PMCID: PMC6098135 DOI: 10.1038/s41598-018-30941-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 08/08/2018] [Indexed: 11/12/2022] Open
Abstract
Annular dark-field (ADF) imaging by scanning transmission electron microscopy (STEM) is a common technique for material characterization with high spatial resolution. It has been reported that ADF signal is proportional to the nth power of the atomic number Z, i.e., the Z contrast in textbooks and papers. Here we first demonstrate the deviation from the power-law model by quantitative experiments of a few 2D materials (graphene, MoS2 and WS2 monolayers). Then we elucidate ADF signal of single atoms using simulations to clarify the cause of the deviation. Two major causes of the deviation from the power-law model will be pointed out. The present study provides a practical guideline for the usage of the conventional power-law model for ADF imaging.
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Affiliation(s)
- Shunsuke Yamashita
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
| | - Jun Kikkawa
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
| | - Keiichi Yanagisawa
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
| | - Takuro Nagai
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
| | - Kazuo Ishizuka
- HREM Research Inc., 14-48 Matsukazedai, Higashimatsuyama, Saitama, 355-0055, Japan
| | - Koji Kimoto
- National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan.
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Feng B, Lugg NR, Kumamoto A, Ikuhara Y, Shibata N. Direct Observation of Oxygen Vacancy Distribution across Yttria-Stabilized Zirconia Grain Boundaries. ACS NANO 2017; 11:11376-11382. [PMID: 29028310 DOI: 10.1021/acsnano.7b05943] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Crystalline interfaces in materials often govern the macroscopic functional properties owing to their complex structure and chemical inhomogeneity. For ionic crystals, however, such understanding has been precluded by the debatable local anion distribution across crystal interfaces. In this study, using yttria-stabilized zirconia as a model material, the oxygen vacancy distribution across individual grain boundaries was directly quantified by atomic-resolution scanning transmission electron microscopy with ultrahigh-sensitive energy-dispersive X-ray spectroscopy. Combined with dynamical scattering calculations, we unambiguously show that the relative oxygen concentrations increase in four high-angle grain boundaries, indicating that the oxygen vacancies are actually depleted near the grain boundary cores. These results experimentally evidence that the long-range electric interaction is the dominant factor to determine the local point defect distribution at ionic crystal interfaces.
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Affiliation(s)
- Bin Feng
- Institute of Engineering Innovation, The University of Tokyo , 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Nathan R Lugg
- Institute of Engineering Innovation, The University of Tokyo , 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Akihito Kumamoto
- Institute of Engineering Innovation, The University of Tokyo , 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Yuichi Ikuhara
- Institute of Engineering Innovation, The University of Tokyo , 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan
- Nanostructures Research Laboratory, Japan Fine Ceramics Center , 2-4-1 Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587, Japan
| | - Naoya Shibata
- Institute of Engineering Innovation, The University of Tokyo , 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan
- Nanostructures Research Laboratory, Japan Fine Ceramics Center , 2-4-1 Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587, Japan
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13
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The impact of STEM aberration correction on materials science. Ultramicroscopy 2017; 180:22-33. [DOI: 10.1016/j.ultramic.2017.03.020] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 03/04/2017] [Accepted: 03/16/2017] [Indexed: 11/22/2022]
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14
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Baumans XDA, Lombardo J, Brisbois J, Shaw G, Zharinov VS, He G, Yu H, Yuan J, Zhu B, Jin K, Kramer RBG, de Vondel JV, Silhanek AV. Healing Effect of Controlled Anti-Electromigration on Conventional and High-T c Superconducting Nanowires. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2017; 13:1700384. [PMID: 28544388 DOI: 10.1002/smll.201700384] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 04/04/2017] [Indexed: 06/07/2023]
Abstract
The electromigration process has the potential capability to move atoms one by one when properly controlled. It is therefore an appealing tool to tune the cross section of monoatomic compounds with ultimate resolution or, in the case of polyatomic compounds, to change the stoichiometry with the same atomic precision. As demonstrated here, a combination of electromigration and anti-electromigration can be used to reversibly displace atoms with a high degree of control. This enables a fine adjustment of the superconducting properties of Al weak links, whereas in Nb the diffusion of atoms leads to a more irreversible process. In a superconductor with a complex unit cell (La2-x Cex CuO4 ), the electromigration process acts selectively on the oxygen atoms with no apparent modification of the structure. This allows to adjust the doping of this compound and switch from a superconducting to an insulating state in a nearly reversible fashion. In addition, the conditions needed to replace feedback controlled electromigration by a simpler technique of electropulsing are discussed. These findings have a direct practical application as a method to explore the dependence of the characteristic parameters on the exact oxygen content and pave the way for a reversible control of local properties of nanowires.
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Affiliation(s)
- Xavier D A Baumans
- Experimental Physics of Nanostructured Materials, Q-MAT, CESAM, Université de Liège, B-4000, Sart Tilman, Belgium
| | - Joseph Lombardo
- Experimental Physics of Nanostructured Materials, Q-MAT, CESAM, Université de Liège, B-4000, Sart Tilman, Belgium
| | - Jérémy Brisbois
- Experimental Physics of Nanostructured Materials, Q-MAT, CESAM, Université de Liège, B-4000, Sart Tilman, Belgium
| | - Gorky Shaw
- Experimental Physics of Nanostructured Materials, Q-MAT, CESAM, Université de Liège, B-4000, Sart Tilman, Belgium
| | - Vyacheslav S Zharinov
- INPAC - Institute for Nanoscale Physics and Chemistry, Department of Physics and Astronomy, KU Leuven, B-3001, Leuven, Belgium
| | - Ge He
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Heshan Yu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Jie Yuan
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Beiyi Zhu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Kui Jin
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Roman B G Kramer
- Université Grenoble Alpes, Institut NEEL, F-38000, Grenoble, France
- CNRS, Institut NEEL, F-38000, Grenoble, France
| | - Joris Van de Vondel
- INPAC - Institute for Nanoscale Physics and Chemistry, Department of Physics and Astronomy, KU Leuven, B-3001, Leuven, Belgium
| | - Alejandro V Silhanek
- Experimental Physics of Nanostructured Materials, Q-MAT, CESAM, Université de Liège, B-4000, Sart Tilman, Belgium
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15
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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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16
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Horide T, Kametani F, Yoshioka S, Kitamura T, Matsumoto K. Structural Evolution Induced by Interfacial Lattice Mismatch in Self-Organized YBa 2Cu 3O 7-δ Nanocomposite Film. ACS NANO 2017; 11:1780-1788. [PMID: 28094494 DOI: 10.1021/acsnano.6b07716] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Intriguing properties of self-organized nanocomposites of perovskite oxides are usually derived from the complex interface of constituent material phases. A sophisticated control of such a system is required for a broad range of energy and device applications, which demand a comprehensive understanding of the interface at the atomic scale. Here, we visualized and theoretically modeled the highly elastically strained nanorod, the interface region with misfit dislocations and heterointerface distortion, and the matrix with strain-induced oxygen vacancies in the self-organized YBa2Cu3O7-δ nanocomposite films with Ba perovskite nanorods. Large misfit strain was elastically accommodated in the nanocomposites, but since the elastic strain was mainly accommodated by the nanorods, the concentration of strain-induced oxygen vacancies was small enough for the matrix to keep high critical temperature (>85 K). The interfacial bonding distorted the atomic structure of YBa2Cu3O7-δ, but the thickness of distortion was limited to a few unit cells (less than the coherence length) due to the electron screening. The effect of volume fraction on elastic strain and the electron screening are crucial for strong vortex pinning without significant degradation of both the elementary pinning force and critical temperature in the nanocomposites. Thus, we comprehensively clarified the self-organized nanocomposite structure for on-demand control of superconductivity and oxide functionality in the nanocomposite engineering of perovskite oxides.
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Affiliation(s)
- Tomoya Horide
- Department of Materials Science and Engineering, Kyushu Institute of Technology , 1-1 Sensui-cho, Tobata-ku, Kitakyushu 804-8550, Japan
| | - Fumitake Kametani
- The Applied Superconductivity Center, National High Magnetic Field Laboratory, Florida State University , 2031 E. Paul Dirac Dr #240, Tallahassee, Florida 32310, United States
| | - Satoru Yoshioka
- Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Takanori Kitamura
- Department of Materials Science and Engineering, Kyushu Institute of Technology , 1-1 Sensui-cho, Tobata-ku, Kitakyushu 804-8550, Japan
| | - Kaname Matsumoto
- Department of Materials Science and Engineering, Kyushu Institute of Technology , 1-1 Sensui-cho, Tobata-ku, Kitakyushu 804-8550, Japan
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17
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Nanostructural characterization of artificial pinning centers in PLD-processed REBa 2Cu 3O 7-δ films. Ultramicroscopy 2016; 176:151-160. [PMID: 27908633 DOI: 10.1016/j.ultramic.2016.11.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 11/05/2016] [Accepted: 11/13/2016] [Indexed: 11/20/2022]
Abstract
In the context of high temperature superconductors, pulsed laser deposition derived GdBa2Cu3O7-δ sample with BaHfO3 nanoparticles has been reported to achieve high current density and good IC-B-θ characteristics at high temperatures. Herein, we have carried out a thorough nanostrucural characterization of BaHfO3 nanoparticles embedded in GdBCO matrix using scanning transmission electron microscopy, with an emphasis on the dispersion behavior, morphologies and nanostrain, to understand the role of BaHfO3 nanoparticles.
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18
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Katsukura H, Miyata T, Tomita K, Mizoguchi T. Effect of the van der Waals interaction on the electron energy-loss near edge structure theoretical calculation. Ultramicroscopy 2016; 178:88-95. [PMID: 27477916 DOI: 10.1016/j.ultramic.2016.07.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 07/07/2016] [Accepted: 07/18/2016] [Indexed: 11/28/2022]
Abstract
The effect of the van der Waals (vdW) interaction on the simulation of the electron energy-loss near edge structure (ELNES) by a first-principles band-structure calculation is reported. The effect of the vdW interaction is considered by the Tkatchenko-Scheffler scheme, and the change of the spectrum profile and the energy shift are discussed. We perform calculations on systems in the solid, liquid and gaseous states. The transition energy shifts to lower energy by approximately 0.1eV in the condensed (solid and liquid) systems by introducing the vdW effect into the calculation, whereas the energy shift in the gaseous models is negligible owing to the long intermolecular distance. We reveal that the vdW interaction exhibits a larger effect on the excited state than the ground state owing to the presence of an excited electron in the unoccupied band. Moreover, the vdW effect is found to depend on the local electron density and the molecular coordination. In addition, this study suggests that the detection of the vdW interactions exhibited within materials is possible by a very stable and high resolution observation.
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Affiliation(s)
- Hirotaka Katsukura
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505, Japan
| | - Tomohiro Miyata
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505, Japan
| | - Kota Tomita
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505, Japan
| | - Teruyasu Mizoguchi
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505, Japan.
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19
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Atomically ordered solute segregation behaviour in an oxide grain boundary. Nat Commun 2016; 7:11079. [PMID: 27004614 PMCID: PMC4814580 DOI: 10.1038/ncomms11079] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 02/19/2016] [Indexed: 11/09/2022] Open
Abstract
Grain boundary segregation is a critical issue in materials science because it determines the properties of individual grain boundaries and thus governs the macroscopic properties of materials. Recent progress in electron microscopy has greatly improved our understanding of grain boundary segregation phenomena down to atomistic dimensions, but solute segregation is still extremely challenging to experimentally identify at the atomic scale. Here, we report direct observations of atomic-scale yttrium solute segregation behaviours in an yttria-stabilized-zirconia grain boundary using atomic-resolution energy-dispersive X-ray spectroscopy analysis. We found that yttrium solute atoms preferentially segregate to specific atomic sites at the core of the grain boundary, forming a unique chemically-ordered structure across the grain boundary. Solute segregation is challenging to experimentally identify at the atomic scale. Here, the authors report the direct observation of atomic site-dependent solute segregation behaviour in an yttria-stabilized zirconia grain boundary by atomic-resolution energy-dispersive X-ray spectroscopy.
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20
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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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21
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Stehr JE, Dobrovolsky A, Sukrittanon S, Kuang Y, Tu CW, Chen WM, Buyanova IA. Optimizing GaNP coaxial nanowires for efficient light emission by controlling formation of surface and interfacial defects. NANO LETTERS 2015; 15:242-247. [PMID: 25426571 DOI: 10.1021/nl503454s] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report on identification and control of important nonradiative recombination centers in GaNP coaxial nanowires (NWs) grown on Si substrates in an effort to significantly increase light emitting efficiency of these novel nanostructures promising for a wide variety of optoelectronic and photonic applications. A point defect complex, labeled as DD1 and consisting of a P atom with a neighboring partner aligned along a crystallographic ⟨ 111 ⟩ axis, is identified by optically detected magnetic resonance as a dominant nonradiative recombination center that resides mainly on the surface of the NWs and partly at the heterointerfaces. The formation of DD1 is found to be promoted by the presence of nitrogen and can be suppressed by reducing the strain between the core and shell layers, as well as by protecting the optically active shell by an outer passivating shell. Growth modes employed during the NW growth are shown to play a role. On the basis of these results, we identify the GaP/GaN(y)P(1-y)/GaN(x)P(1-x) (x < y) core/shell/shell NW structure, where the GaN(y)P(1-y) inner shell with the highest nitrogen content serves as an active light-emitting layer, as the optimized and promising design for efficient light emitters based on GaNP NWs.
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Affiliation(s)
- Jan E Stehr
- Department of Physics, Chemistry and Biology, Linköping University , 581 83 Linköping, Sweden
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22
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23
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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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24
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Stevens A, Yang H, Carin L, Arslan I, Browning ND. The potential for Bayesian compressive sensing to significantly reduce electron dose in high-resolution STEM images. Microscopy (Oxf) 2013; 63:41-51. [PMID: 24151325 DOI: 10.1093/jmicro/dft042] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The use of high-resolution imaging methods in scanning transmission electron microscopy (STEM) is limited in many cases by the sensitivity of the sample to the beam and the onset of electron beam damage (for example, in the study of organic systems, in tomography and during in situ experiments). To demonstrate that alternative strategies for image acquisition can help alleviate this beam damage issue, here we apply compressive sensing via Bayesian dictionary learning to high-resolution STEM images. These computational algorithms have been applied to a set of images with a reduced number of sampled pixels in the image. For a reduction in the number of pixels down to 5% of the original image, the algorithms can recover the original image from the reduced data set. We show that this approach is valid for both atomic-resolution images and nanometer-resolution studies, such as those that might be used in tomography datasets, by applying the method to images of strontium titanate and zeolites. As STEM images are acquired pixel by pixel while the beam is scanned over the surface of the sample, these postacquisition manipulations of the images can, in principle, be directly implemented as a low-dose acquisition method with no change in the electron optics or the alignment of the microscope itself.
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Affiliation(s)
- Andrew Stevens
- National Security Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
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25
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Van Tendeloo G, Bals S, Van Aert S, Verbeeck J, Van Dyck D. Advanced electron microscopy for advanced materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2012; 24:5655-5675. [PMID: 22907862 DOI: 10.1002/adma.201202107] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Indexed: 06/01/2023]
Abstract
The idea of this Review is to introduce newly developed possibilities of advanced electron microscopy to the materials science community. Over the last decade, electron microscopy has evolved into a full analytical tool, able to provide atomic scale information on the position, nature, and even the valency atoms. This information is classically obtained in two dimensions (2D), but can now also be obtained in 3D. We show examples of applications in the field of nanoparticles and interfaces.
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26
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Klie RF, Qiao Q, Paulauskas T, Gulec A, Rebola A, Öğüt S, Prange MP, Idrobo JC, Pantelides ST, Kolesnik S, Dabrowski B, Ozdemir M, Boyraz C, Mazumdar D, Gupta A. Observations of Co4+ in a higher spin state and the increase in the Seebeck coefficient of thermoelectric Ca3Co4O9. PHYSICAL REVIEW LETTERS 2012; 108:196601. [PMID: 23003068 DOI: 10.1103/physrevlett.108.196601] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Indexed: 06/01/2023]
Abstract
Ca3Co4O9 has a unique structure that leads to exceptionally high thermoelectric transport. Here we report the achievement of a 27% increase in the room-temperature in-plane Seebeck coefficient of Ca3Co4O9 thin films. We combine aberration-corrected Z-contrast imaging, atomic-column resolved electron energy-loss spectroscopy, and density-functional calculations to show that the increase is caused by stacking faults with Co4+-ions in a higher spin state compared to that of bulk Ca3Co4O9. The higher Seebeck coefficient makes the Ca3Co4O9 system suitable for many high temperature waste-heat-recovery applications.
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Affiliation(s)
- R F Klie
- Department of Physics, University of Illinois at Chicago, Chicago, Illinois, USA
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27
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Llordés A, Palau A, Gázquez J, Coll M, Vlad R, Pomar A, Arbiol J, Guzmán R, Ye S, Rouco V, Sandiumenge F, Ricart S, Puig T, Varela M, Chateigner D, Vanacken J, Gutiérrez J, Moshchalkov V, Deutscher G, Magen C, Obradors X. Nanoscale strain-induced pair suppression as a vortex-pinning mechanism in high-temperature superconductors. NATURE MATERIALS 2012; 11:329-336. [PMID: 22327747 DOI: 10.1038/nmat3247] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Accepted: 01/11/2012] [Indexed: 05/31/2023]
Abstract
Boosting large-scale superconductor applications require nanostructured conductors with artificial pinning centres immobilizing quantized vortices at high temperature and magnetic fields. Here we demonstrate a highly effective mechanism of artificial pinning centres in solution-derived high-temperature superconductor nanocomposites through generation of nanostrained regions where Cooper pair formation is suppressed. The nanostrained regions identified from transmission electron microscopy devise a very high concentration of partial dislocations associated with intergrowths generated between the randomly oriented nanodots and the epitaxial YBa(2)Cu(3)O(7) matrix. Consequently, an outstanding vortex-pinning enhancement correlated to the nanostrain is demonstrated for four types of randomly oriented nanodot, and a unique evolution towards an isotropic vortex-pinning behaviour, even in the effective anisotropy, is achieved as the nanostrain turns isotropic. We suggest a new vortex-pinning mechanism based on the bond-contraction pairing model, where pair formation is quenched under tensile strain, forming new and effective core-pinning regions.
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Affiliation(s)
- A Llordés
- Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
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28
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Appavoo K, Lei DY, Sonnefraud Y, Wang B, Pantelides ST, Maier SA, Haglund RF. Role of defects in the phase transition of VO2 nanoparticles probed by plasmon resonance spectroscopy. NANO LETTERS 2012; 12:780-786. [PMID: 22273268 DOI: 10.1021/nl203782y] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Defects are known to affect nanoscale phase transitions, but their specific role in the metal-to-insulator transition in VO(2) has remained elusive. By combining plasmon resonance nanospectroscopy with density functional calculations, we correlate decreased phase-transition energy with oxygen vacancies created by strain at grain boundaries. By measuring the degree of metallization in the lithographically defined VO(2) nanoparticles, we find that hysteresis width narrows with increasing size, thus illustrating the potential for domain boundary engineering in phase-changing nanostructures.
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Affiliation(s)
- Kannatassen Appavoo
- Interdisciplinary Program in Materials Science, Vanderbilt University, Nashville, Tennessee 37235-0106, USA.
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29
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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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30
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Atom-resolved imaging of ordered defect superstructures at individual grain boundaries. Nature 2011; 479:380-3. [DOI: 10.1038/nature10593] [Citation(s) in RCA: 196] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 09/21/2011] [Indexed: 11/08/2022]
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31
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Cantoni C, Gao Y, Wee SH, Specht ED, Gazquez J, Meng J, Pennycook SJ, Goyal A. Strain-driven oxygen deficiency in self-assembled, nanostructured, composite oxide films. ACS NANO 2011; 5:4783-9. [PMID: 21604819 DOI: 10.1021/nn2007628] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Oxide self-assembly is a promising bottom-up approach for fabricating new composite materials at the nanometer length scale. Tailoring the properties of such systems for a wide range of electronic applications depends on the fundamental understanding of the interfaces between the constituent phases. We show that the nanoscale strain modulation in self-assembled systems made of high-T(c) superconducting films containing nanocolumns of BaZrO(3) strongly affects the oxygen composition of the superconductor. Our findings explain the observed reduction of the superconducting critical temperature.
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Affiliation(s)
- Claudia Cantoni
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6116, Unites States.
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32
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Kim HS, Bi L, Paik H, Yang DJ, Park YC, Dionne GF, Ross CA. Self-assembled single-phase perovskite nanocomposite thin films. NANO LETTERS 2010; 10:597-602. [PMID: 20039695 DOI: 10.1021/nl903611t] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Thin films of perovskite-structured oxides with general formula ABO(3) have great potential in electronic devices because of their unique properties, which include the high dielectric constant of titanates, (1) high-T(C) superconductivity in cuprates, (2) and colossal magnetoresistance in manganites. (3) These properties are intimately dependent on, and can therefore be tailored by, the microstructure, orientation, and strain state of the film. Here, we demonstrate the growth of cubic Sr(Ti,Fe)O(3) (STF) films with an unusual self-assembled nanocomposite microstructure consisting of (100) and (110)-oriented crystals, both of which grow epitaxially with respect to the Si substrate and which are therefore homoepitaxial with each other. These structures differ from previously reported self-assembled oxide nanocomposites, which consist either of two different materials (4-7) or of single-phase distorted-cubic materials that exhibit two or more variants. (8-12) Moreover, an epitaxial nanocomposite SrTiO(3) overlayer can be grown on the STF, extending the range of compositions over which this microstructure can be formed. This offers the potential for the implementation of self-organized optical/ferromagnetic or ferromagnetic/ferroelectric hybrid nanostructures integrated on technologically important Si substrates with applications in magnetooptical or spintronic devices.
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Affiliation(s)
- Hyun-Suk Kim
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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33
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Rulis P, Lupini A, Pennycook S, Ching W. Spectroscopic imaging of electron energy loss spectra using ab initio data and function field visualization. Ultramicroscopy 2009; 109:1472-8. [DOI: 10.1016/j.ultramic.2009.08.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Revised: 07/28/2009] [Accepted: 08/18/2009] [Indexed: 11/26/2022]
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34
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van der Laan DC, Haugan TJ, Barnes PN. Effect of a compressive uniaxial strain on the critical current density of grain boundaries in superconducting YBa2Cu3O7-delta films. PHYSICAL REVIEW LETTERS 2009; 103:027005. [PMID: 19659238 DOI: 10.1103/physrevlett.103.027005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Indexed: 05/28/2023]
Abstract
The mechanism by which grain boundaries impede current flow in high-temperature superconductors has resisted explanation for over two decades. We provide evidence that the strain fields around grain boundary dislocations in YBa2Cu3O7-delta thin films substantially suppress the local critical current density Jc. The removal of strain from the superconducting grain boundary channels by the application of compressive strain causes a remarkable increase in Jc. Contrary to previous understanding, the strain-free Jc of the grain boundary channels is comparable to the intrinsic Jc of the grains themselves.
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Affiliation(s)
- D C van der Laan
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
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35
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Inada H, Wu L, Wall J, Su D, Zhu Y. Performance and image analysis of the aberration-corrected Hitachi HD-2700C STEM. JOURNAL OF ELECTRON MICROSCOPY 2009; 58:111-122. [PMID: 19254916 DOI: 10.1093/jmicro/dfp011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We report the performance of the first aberration-corrected scanning transmission electron microscope (STEM) manufactured by Hitachi. We describe its unique features and versatile capabilities in atomic-scale characterization and its applications in materials research. We also discuss contrast variation of the STEM images obtained from different annular dark-field (ADF) detectors of the instrument, and the increased complexity in contrast interpretation and quantification due to the increased convergent angles of the electron probe associated with the aberration corrector. We demonstrate that the intensity of atomic columns in an ADF image depends strongly on a variety of imaging parameters, sample thickness, as well as the nuclear charge and the deviation from their periodic position of the atoms we are probing. Image simulations are often required to correctly interpret the atomic structure of an ADF-STEM image.
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Affiliation(s)
- Hiromi Inada
- Brookhaven National Laboratory, Upton, NY 11973, USA
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36
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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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Klie RF, Walkosz W, Yang G, Zhao Y. Aberration-corrected Z-contrast imaging of SrTiO3 dislocation cores. JOURNAL OF ELECTRON MICROSCOPY 2009; 58:185-191. [PMID: 19074689 DOI: 10.1093/jmicro/dfn026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Many fundamental problems in materials science, physics, and particular nanotechnology rely on the direct determination and characterization of atomic arrangements and electronic environments of individual interfaces or defects. In this paper, we will show how aberration-corrected Z-contrast imaging in combination with electron energy-loss spectroscopy can be used to directly measure the local atomic and electronic structures of dislocation cores in low-angle SrTiO3 [001] tilt grain boundaries. In particular, we will study two types of dislocation cores in a 3 degrees tilt grain boundary, a pure edge dislocation, and a dissociated dislocation core. While it is energetically favorable for an edge dislocation to dissociate into two partial dislocations in such a low-angle grain boundary, we can find pure edge dislocations that show a higher O vacancy concentration than the dissociated cores. We suggest that the increased oxygen vacancy concentration might help stabilizing the pure edge dislocations in 3 degrees tilt grain boundaries of SrTiO3.
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Affiliation(s)
- R F Klie
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA.
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Tanaka I, Mizoguchi T. First-principles calculations of x-ray absorption near edge structure and energy loss near edge structure: present and future. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:104201. [PMID: 21817421 DOI: 10.1088/0953-8984/21/10/104201] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Computational methods for theoretical x-ray absorption near edge structure (XANES) and energy loss near edge structure (ELNES) are classified into a few groups. Depending on the absorption (or excitation) edge, required accuracy and desired information, one needs to select the most suitable method. In this paper, after providing a map of available computational methods, some examples of first-principles calculations of XANES/ELNES for selected wide gap materials are given together with references. For ZnO, for example, experimental spectra at three edges, Zn K, L(3), and O K, including their orientation dependence, are well reproduced by the supercell calculations with a core hole. Good agreement between theoretical and experimental spectra of ZnO alloys can also be seen. Theoretical fingerprints are satisfactorily obtained in this way. However, there are remaining issues beyond 'good agreements' which need to be solved in the future.
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Affiliation(s)
- Isao Tanaka
- Department of Materials Science and Engineering, Kyoto University, Sakyo, Kyoto 606-8501, Japan. Nanostructures Research Laboratory, Japan Fine Ceramics Center, Atsuta, Nagoya 456-8587, Japan
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Mizoguchi T, Tanaka I, Gao SP, Pickard CJ. First-principles calculation of spectral features, chemical shift and absolute threshold of ELNES and XANES using a plane wave pseudopotential method. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:104204. [PMID: 21817424 DOI: 10.1088/0953-8984/21/10/104204] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Spectral features, chemical shifts, and absolute thresholds of electron energy loss near-edge structure (ELNES) and x-ray absorption near-edge structure (XANES) for selected compounds, i.e. TiO(2) (rutile), TiO(2) (anatase), SrTiO(3), Ti(2)O(3), Al(2)O(3), AlN and β-Ga(2)O(3), were calculated by a plane wave pseudopotential method. Experimental ELNES/XANES of those compounds were well reproduced when an excited pseudopotential, which includes a core hole, was used. In addition to the spectral features, it was found that chemical shifts among different compounds were also reproduced by correcting the contribution of the excited pseudopotentials to the energy of the core orbital.
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Affiliation(s)
- Teruyasu Mizoguchi
- Institute of Engineering Innovation, University of Tokyo, 2-11-16, Yayoi, Bunkyo, Tokyo 113-8656, Japan
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Acha C, Rozenberg MJ. Non-volatile resistive switching in the dielectric superconductor YBa(2)Cu(3)O(7-δ). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:045702. [PMID: 21715820 DOI: 10.1088/0953-8984/21/4/045702] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report on the reversible, non-volatile and polarity-dependent resistive switching between superconductor and insulator states at the interfaces of an Au/YBa(2)Cu(3)O(7-δ) (YBCO)/Au system. We show that, upon application of electric pulses, the superconducting state of YBCO in regions near the electrodes can be reversibly removed and restored. In addition, four-wire measurements reveal that pulsing also induces significant non-volatile changes in the bulk resistance. We argue that our observations are compatible with a scenario where the switching effect is due to migration of oxygen ions along grain boundaries that control the inter-grain superconducting coupling.
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Affiliation(s)
- C Acha
- Departamento de Física, FCEyN, Universidad de Buenos Aires, Ciudad Universitaria, (C1428EHA) Buenos Aires, Argentina
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Abstract
The technological advances predicted (or, perhaps, demanded) for the twenty-first century are intimately linked to the crystallochemically controlled synthesis of high-performance functional materials. To answer the new hendiatris of ‘smaller, faster, better’, the manufacture of these materials as nanoparticles has become a scientific
noblesse oblige
. Direct incorporation into the next generation of electronic devices will necessitate anisotropic forms of these materials, be they nanowires, nanotapes or nanotubes. Chemists have recently discovered that, in addition to the classical methods of anisotropic growth, new routes allow more complex materials to be synthesized in these morphologies. This review describes, using a series of examples, how the morphology of functional materials can be controlled using templated growth mediated by a biopolymer. By involving a biopolymer in the synthetic protocol, anisotropic nanoparticles and assemblages of even quite complex materials can be generated in syntheses that are simple, elegant and highly specific.
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Affiliation(s)
- Simon R Hall
- School of Chemistry, University of BristolBristol BS81TS, UK
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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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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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Zhu Y, Wall J. Chapter 12 Aberration-Corrected Electron Microscopes at Brookhaven Microscopes at Brookhaven National Laboratory. ADVANCES IN IMAGING AND ELECTRON PHYSICS 2008. [DOI: 10.1016/s1076-5670(08)01012-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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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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Mizoguchi T, Tatsumi K, Tanaka I. Peak assignments of ELNES and XANES using overlap population diagrams. Ultramicroscopy 2006; 106:1120-8. [PMID: 16870343 DOI: 10.1016/j.ultramic.2006.04.027] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Revised: 12/15/2005] [Accepted: 04/06/2006] [Indexed: 10/24/2022]
Abstract
The usefulness of overlap population (OP) diagrams for peak assignments of an electron energy loss near-edge structure (ELNES) and an X-ray absorption near-edge structure (XANES) is demonstrated. Mg-K, L(2,3), and O-K edges of MgO are taken as examples. Theoretical calculations are performed using a first-principles orthogonalized linear combination of atomic orbitals (OLCAO) method. A core-hole is included explicitly, and a large supercell is used to minimize artificial interactions among the core-holes in adjacent cells. All experimental spectra are quantitatively reproduced by the calculations. The OP diagrams for a selected pair of atomic orbitals are computed in order to provide proper assignments for each peak in ELNES and XANES. They are interpreted in terms of interactions among Mg-Mg and Mg-O bonds. Results are found to be consistent to our previous conclusion, which was obtained using a cluster method [T. Mizoguchi, et al., Phys. Rev. B 61 (2000) 2180]. The powerful combination of the OP diagram and a high-energy resolution ELNES to obtain fine electronic structures is also demonstrated.
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Affiliation(s)
- Teruyasu Mizoguchi
- National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, One Cyclotron Road, MS 72-105, Berkeley, CA 94720, USA.
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Sato Y, Buban JP, Mizoguchi T, Shibata N, Yodogawa M, Yamamoto T, Ikuhara Y. Role of Pr segregation in acceptor-state formation at ZnO grain boundaries. PHYSICAL REVIEW LETTERS 2006; 97:106802. [PMID: 17025842 DOI: 10.1103/physrevlett.97.106802] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2006] [Indexed: 05/12/2023]
Abstract
The role of Pr doping on double Schottky barrier formations at ZnO single grain boundaries was investigated by the combination of current-voltage measurements, atomic-resolution Z-contrast scanning transmission electron microscopy, and first-principles calculations. Although Pr segregated to the specific atomic site along the boundaries, it was found not to be the direct cause of nonlinear current-voltage properties. Instead, under appropriate annealing conditions, Pr enhances formations of acceptor-type native defects that are essential for the creation of double Schottky barriers in ZnO.
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Affiliation(s)
- Yukio Sato
- Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
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Dark C, Kilburn MR, Hammerl G, Schneider C, Mannhart J, Grovenor CRM. NanoSIMS analysis of Ca doping at a grain boundary in a superconducting YBCO Ca-123/123 bicrystal. ACTA ACUST UNITED AC 2006. [DOI: 10.1088/1742-6596/43/1/068] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Browning ND, Arslan I, Erni R, Idrobo JC, Ziegler A, Bradley J, Dai Z, Stach EA, Bleloch A. Monochromators and Aberration Correctors: Taking EELS to New Levels of Energy and Spatial Resolution. ACTA ACUST UNITED AC 2006. [DOI: 10.1088/1742-6596/26/1/014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Tomita T, Schilling JS, Chen L, Veal BW, Claus H. Enhancement of the critical current density of YBa2Cu3Ox superconductors under hydrostatic pressure. PHYSICAL REVIEW LETTERS 2006; 96:077001. [PMID: 16606126 DOI: 10.1103/physrevlett.96.077001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2005] [Indexed: 05/08/2023]
Abstract
The dependence of the critical current density Jc on hydrostatic pressure to 0.6 GPa is determined for a single 25 degrees [001]-tilt grain boundary in a bicrystalline ring of nearly optimally doped melt-textured YBa2Cu3Ox. Jc is found to increase rapidly under pressure at +20%/GPa. A new diagnostic method is introduced (pressure-induced Jc relaxation) which reveals a sizable concentration of vacant oxygen sites in the grain boundary region. Completely filling such sites with oxygen anions should lead to significant enhancements in Jc.
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Affiliation(s)
- T Tomita
- Department of Physics, Washington University, CB 1105, One Brookings Drive, St. Louis, Missouri 63130, USA
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