1
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Ni J, Cao L, Zhong B, Li Q, Guo C, Song J, Liu Y, Lu M, Fan T. Characterizing Local Electronic States of Twin Boundaries in Copper. NANO LETTERS 2024; 24:5474-5480. [PMID: 38652833 DOI: 10.1021/acs.nanolett.4c00550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
Grain boundaries (GBs) and twin boundaries (TBs) in copper (Cu) are two major planar defects that influence electrical conductivity due to their complex electron transport characteristics, involving electron scattering and electron concentration. Understanding their local electronic states is crucial for the design of future conductor materials. In this study, we characterized electron behaviors at TBs and GBs within one Cu grain using atomic force microscopy. Our findings revealed that, compared with GBs, TBs exhibit better current transport capability (direct-current mode) and larger electromagnetic loss (high-frequency microwave mode). Both kelvin probe force microscopy and theoretical analysis suggested that TBs with smaller lattice disorder possess lower density of states at the Fermi level. The reduced density of states may result in decreased electron scattering and a lower electron concentration at TBs. The latter can be highlighted by the high-frequency skinning effect, manifested as larger electromagnetic loss and weaker high-frequency conductivity.
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Affiliation(s)
- Jiamiao Ni
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Lin Cao
- National Laboratory of Solid-State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, People's Republic of China
| | - Boan Zhong
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Quan Li
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Chongxiao Guo
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Jian Song
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Yue Liu
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Minghui Lu
- National Laboratory of Solid-State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, People's Republic of China
| | - Tongxiang Fan
- State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
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2
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Ijaz S, Raza E, Ahmad Z, Mehmood H, Zubair M, Mehmood MQ, Massoud Y. A numerical approach to optimize the performance of HTL-free carbon electrode-based perovskite solar cells using organic ETLs. Heliyon 2024; 10:e29091. [PMID: 38596139 PMCID: PMC11002682 DOI: 10.1016/j.heliyon.2024.e29091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 02/16/2024] [Accepted: 03/31/2024] [Indexed: 04/11/2024] Open
Abstract
Carbon electrode-based perovskite solar cells (c-PSCs) without a hole transport layer (HTL) have obtained a significant interest owing to their cost-effective, stable, and simplified structure. However, their application is limited by low efficiency and the prevalence of high-temperature processed electron transport layer (ETL), e.g. TiO2, which also has poor optoelectronic properties, including low conductivity and mobility. In this study, a series of organic materials, namely PCBM ((Park et al., 2023; Park et al., 2023) [6,6]-phenyl-C61-butyric acid methyl ester, C72H14O2), Alq3 (Al(C9H6NO)3), BCP (2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline, C26H20N2), C60, ICBA (indene-C60 bisadduct, C78H16) and PEIE (poly (ethylenimine) ethoxylated, (C37H24O6N2)n) have been numerically analyzed in SCAPS-1D solar simulator to explore alternative potential ETL materials for HTL-free c-PSCs. The presented device has FTO/ETL/CH3NH3PbI3/carbon structure, and its performance is optimized based on significant design parameters. The highest achieved PCEs for PCBM, Alq3, BCP, C60, ICBA, and PEIE-based devices are 22.85%, 19.08%, 20.99%, 25.51%, 23.91%, and 22.53%, respectively. These PCEs are obtained for optimum absorber thickness for each case, with an acceptor concentration of 1.0 × 1017 cm-3 and defect density of 2.5 × 1013 cm-3. The C60-based cell has been found to outperform with device parameters as Voc of 1.29 V, Jsc of 23.76 mA/cm2, and FF of 82.67%. As the design lacks stability when only organic materials are employed, each of the presented devices have been analyzed by applying BiI3, LiF, and ZnO as protective layers with the performances not compromised. We believe that our obtained results will be of great interest in developing stable and efficient HTL-free c-PSCs.
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Affiliation(s)
- Sumbel Ijaz
- Department of Electrical Engineering, Information Technology University of the Punjab (ITU), 54000 Lahore, Pakistan
| | - Ehsan Raza
- Qatar University Young Scientists Center (QUYSC), Qatar University, 2713, Doha, Qatar
| | - Zubair Ahmad
- Qatar University Young Scientists Center (QUYSC), Qatar University, 2713, Doha, Qatar
| | - Haris Mehmood
- Department of Electrical Engineering, Information Technology University of the Punjab (ITU), 54000 Lahore, Pakistan
| | - Muhammad Zubair
- Innovative Technologies Laboratories (ITL), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia
| | - Muhammad Qasim Mehmood
- Department of Electrical Engineering, Information Technology University of the Punjab (ITU), 54000 Lahore, Pakistan
| | - Yehia Massoud
- Innovative Technologies Laboratories (ITL), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia
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3
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Chen J, Zhou Y, Huang X, Yu C, Han D, Wang A, Zhu Y, Shi K, Kang Q, Li P, Jiang P, Qian X, Bao H, Li S, Wu G, Zhu X, Wang Q. Ladderphane copolymers for high-temperature capacitive energy storage. Nature 2023; 615:62-66. [PMID: 36859585 DOI: 10.1038/s41586-022-05671-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Accepted: 12/19/2022] [Indexed: 03/03/2023]
Abstract
For capacitive energy storage at elevated temperatures1-4, dielectric polymers are required to integrate low electrical conduction with high thermal conductivity. The coexistence of these seemingly contradictory properties remains a persistent challenge for existing polymers. We describe here a class of ladderphane copolymers exhibiting more than one order of magnitude lower electrical conductivity than the existing polymers at high electric fields and elevated temperatures. Consequently, the ladderphane copolymer possesses a discharged energy density of 5.34 J cm-3 with a charge-discharge efficiency of 90% at 200 °C, outperforming the existing dielectric polymers and composites. The ladderphane copolymers self-assemble into highly ordered arrays by π-π stacking interactions5,6, thus giving rise to an intrinsic through-plane thermal conductivity of 1.96 ± 0.06 W m-1 K-1. The high thermal conductivity of the copolymer film permits efficient Joule heat dissipation and, accordingly, excellent cyclic stability at elevated temperatures and high electric fields. The demonstration of the breakdown self-healing ability of the copolymer further suggests the promise of the ladderphane structures for high-energy-density polymer capacitors operating under extreme conditions.
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Affiliation(s)
- Jie Chen
- Shanghai Key Laboratory of Electrical Insulation and Thermal Ageing, Department of Polymer Science and Engineering, Frontiers Science Center for Transformative Molecules, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China
| | - Yao Zhou
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Xingyi Huang
- Shanghai Key Laboratory of Electrical Insulation and Thermal Ageing, Department of Polymer Science and Engineering, Frontiers Science Center for Transformative Molecules, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China.
| | - Chunyang Yu
- Shanghai Key Laboratory of Electrical Insulation and Thermal Ageing, Department of Polymer Science and Engineering, Frontiers Science Center for Transformative Molecules, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China
| | - Donglin Han
- School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Ao Wang
- University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai, China
| | - Yingke Zhu
- Shanghai Key Laboratory of Electrical Insulation and Thermal Ageing, Department of Polymer Science and Engineering, Frontiers Science Center for Transformative Molecules, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China
| | - Kunming Shi
- Shanghai Key Laboratory of Electrical Insulation and Thermal Ageing, Department of Polymer Science and Engineering, Frontiers Science Center for Transformative Molecules, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China
| | - Qi Kang
- Shanghai Key Laboratory of Electrical Insulation and Thermal Ageing, Department of Polymer Science and Engineering, Frontiers Science Center for Transformative Molecules, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China
| | - Pengli Li
- Shanghai Key Laboratory of Electrical Insulation and Thermal Ageing, Department of Polymer Science and Engineering, Frontiers Science Center for Transformative Molecules, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China
| | - Pingkai Jiang
- Shanghai Key Laboratory of Electrical Insulation and Thermal Ageing, Department of Polymer Science and Engineering, Frontiers Science Center for Transformative Molecules, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China
| | - Xiaoshi Qian
- School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Hua Bao
- University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai, China
| | - Shengtao Li
- State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an, China
| | - Guangning Wu
- Research Institute of Future Technology, School of Electrical Engineering, Southwest Jiaotong University, Chengdu, China
| | - Xinyuan Zhu
- Shanghai Key Laboratory of Electrical Insulation and Thermal Ageing, Department of Polymer Science and Engineering, Frontiers Science Center for Transformative Molecules, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China
| | - Qing Wang
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, USA.
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4
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Wang C, Wang Z, Mao S, Chen Z, Wang Y. Coordination environment of active sites and their effect on catalytic performance of heterogeneous catalysts. CHINESE JOURNAL OF CATALYSIS 2022. [DOI: 10.1016/s1872-2067(21)63924-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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5
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Smeu M, Leung K. Electron leakage through heterogeneous LiF on lithium-metal battery anodes. Phys Chem Chem Phys 2021; 23:3214-3218. [PMID: 33533339 DOI: 10.1039/d0cp06310j] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The solid-electrolyte interphase (SEI) that forms on lithium ion battery (LIB) anodes prevents degradation-causing transfer of electrons to the electrolyte. Grain boundaries (GBs) between different SEI components, like LiF, have been suggested to accelerate Li+ transport. However, using the non-equilibrium Green's function technique with density functional theory (NEGF-DFT), we find that GBs enhance electron tunneling in thin LiF films by 1-2 orders of magnitude, depending on the bias. Extrapolating to thicker films using the Wentzel-Kramers-Brillouin (WKB) method emphasizes that safer batteries require passivation of GBs in the SEI.
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Affiliation(s)
- Manuel Smeu
- Department of Physics, Binghamton University - SUNY, Binghamton, NY 13902, USA.
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6
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Dubrovin V, Popov AA, Avdoshenko SM. Valence electrons in lanthanide-based single-atom magnets: a paradigm shift in 4f-magnetism modeling and design. Inorg Chem Front 2021. [DOI: 10.1039/d0qi01148g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Impact of valence electrons on the magnetic properties of lanthanide-based monatomic magnetic systems on surfaces and in molecules. And FV-magnetism - as a crucial bit in the further understanding and design of a new generation of atomic magnets.
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7
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Accurate atomic electron affinities calculated by using anionic Gaussian basis sets. Theor Chem Acc 2020. [DOI: 10.1007/s00214-020-02629-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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8
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Wei J, Ogawa T, Feng B, Yokoi T, Ishikawa R, Kuwabara A, Matsunaga K, Shibata N, Ikuhara Y. Direct Measurement of Electronic Band Structures at Oxide Grain Boundaries. NANO LETTERS 2020; 20:2530-2536. [PMID: 32134272 DOI: 10.1021/acs.nanolett.9b05298] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Grain boundaries (GBs) modulate the macroscopic properties in polycrystalline materials because they have different atomic and electronic structures from the bulk. Despite the progress on the understanding of GB atomic structures, knowledge of the localized electronic band structures is still lacking. Here, we experimentally characterized the atomic structures and the band gaps of four typical GBs in α-Al2O3 by scanning transmission electron microscopy and valence electron energy-loss spectroscopy (EELS). It was found that the band gaps of the GBs are narrowed by 0.5-2.1 eV compared with that of 8.8 eV in the bulk. By combing core-loss EELS with first-principles calculations, we elucidated that the band gap reductions directly correlate with the decrease of the coordination numbers of Al and O ions at the GBs. These results provide in-depth understanding between the local atomic and electronic band structures for GBs and demonstrate a novel electronic-structure analysis for crystalline defects.
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Affiliation(s)
- Jiake Wei
- Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656, Japan
| | - Takafumi Ogawa
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587, Japan
| | - Bin Feng
- Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656, Japan
| | - Tatsuya Yokoi
- Department of Materials Physics, Nagoya University, Nagoya 464-8601, Japan
| | - Ryo Ishikawa
- Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656, Japan
- Japan Science and Technology Agency, PRESTO, Kawaguchi, Saitama 332-0012, Japan
| | - Akihide Kuwabara
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587, Japan
| | - Katsuyuki Matsunaga
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587, Japan
- Department of Materials Physics, Nagoya University, Nagoya 464-8601, Japan
| | - Naoya Shibata
- Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656, Japan
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587, Japan
| | - Yuichi Ikuhara
- Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656, Japan
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587, Japan
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9
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Yin D, Chen C, Saito M, Inoue K, Ikuhara Y. Ceramic phases with one-dimensional long-range order. NATURE MATERIALS 2019; 18:19-23. [PMID: 30542098 DOI: 10.1038/s41563-018-0240-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 11/01/2018] [Indexed: 06/09/2023]
Abstract
Solids are generally classified into three categories based on their atomic arrangement: crystalline, quasicrystalline and amorphous1-4. Here we report MgO and Nd2O3 ceramic phases with special atomic arrangements that should belong to a category of solids different from these three well known categories by combining state-of-the-art atomic-resolution scanning transmission electron microscopy and first-principles calculations. The reported solid structure exhibits a one-dimensional (1D) long-range order with a translational periodicity and is composed of structural units that individually have atomic arrangements similar to those observed in coincidence-site lattice configurations present at grain boundaries. Regardless of the insulating nature of the bulk MgO, the bandgap of which is measured to be 7.4 eV, the MgO 1D ordered structure is a wide-bandgap semiconductor with a bandgap of 3.2 eV owing to this special atomic arrangement. The discovery of 1D ordered structures suggests that the structural categories of solids could be more abundant, with physical properties distinct from their regular counterparts.
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Affiliation(s)
- Deqiang Yin
- Advanced Institute for Materials Research, Tohoku University, Aoba-ku, Sendai, Japan
- College of Aerospace Engineering, Chongqing University, Chongqing, China
| | - Chunlin Chen
- Advanced Institute for Materials Research, Tohoku University, Aoba-ku, Sendai, Japan.
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China.
| | - Mitsuhiro Saito
- Advanced Institute for Materials Research, Tohoku University, Aoba-ku, Sendai, Japan
- Institute of Engineering Innovation, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Kazutoshi Inoue
- Advanced Institute for Materials Research, Tohoku University, Aoba-ku, Sendai, Japan
| | - Yuichi Ikuhara
- Advanced Institute for Materials Research, Tohoku University, Aoba-ku, Sendai, Japan.
- Institute of Engineering Innovation, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, Atsuta, Nagoya, Japan.
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10
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Pacchioni G, Freund HJ. Controlling the charge state of supported nanoparticles in catalysis: lessons from model systems. Chem Soc Rev 2018; 47:8474-8502. [DOI: 10.1039/c8cs00152a] [Citation(s) in RCA: 110] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Model systems are very important to identify the working principles of real catalysts, and to develop concepts that can be used in the design of new catalytic materials.
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Affiliation(s)
| | - Hans-Joachim Freund
- Fritz-Haber-Institut der Max-Planck-Gesellschaft
- Department of Chemical Physics
- 14195 Berlin
- Germany
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11
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Haque F, Chenot S, Viñes F, Illas F, Stankic S, Jupille J. ZnO powders as multi-facet single crystals. Phys Chem Chem Phys 2017; 19:10622-10628. [PMID: 28397894 DOI: 10.1039/c7cp01635b] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Oxides are most commonly found in divided forms with properties difficult to control since their crystallographic orientations usually escape analysis. To overcome this an appropriate model system can be provided by ZnO smoke which, obtained by combustion of Zn in air, exhibits nanoparticles with well-defined surface facets. The present work focuses on the interaction of water with ZnO smokes by combining density functional theory based simulations and infrared spectroscopy measurements with applied pressures from 10-7 to 1 mbar. We demonstrate that the use of ultra-high vacuum allows the analysis of the very first stages of the adsorption, and report on water structures on ZnO(112[combining macron]0) for the first time. We further show that ZnO powders behave as multi-facet single crystals involving (101[combining macron]0), (112[combining macron]0), (0001), and (0001[combining macron]) surfaces with the polar orientations corresponding to 25% of the total surface area. A great deal of cross-agreements between experimental results and simulation provides a simple approach for the examination of hydroxylated/hydrated ZnO smokes and can be widely applied on other ZnO-related powders.
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Affiliation(s)
- Francia Haque
- Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75252 Paris Cedex 05, France.
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12
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Bean JJ, Saito M, Fukami S, Sato H, Ikeda S, Ohno H, Ikuhara Y, McKenna KP. Atomic structure and electronic properties of MgO grain boundaries in tunnelling magnetoresistive devices. Sci Rep 2017; 7:45594. [PMID: 28374755 PMCID: PMC5379487 DOI: 10.1038/srep45594] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 02/27/2017] [Indexed: 11/11/2022] Open
Abstract
Polycrystalline metal oxides find diverse applications in areas such as nanoelectronics, photovoltaics and catalysis. Although grain boundary defects are ubiquitous their structure and electronic properties are very poorly understood since it is extremely challenging to probe the structure of buried interfaces directly. In this paper we combine novel plan-view high-resolution transmission electron microscopy and first principles calculations to provide atomic level understanding of the structure and properties of grain boundaries in the barrier layer of a magnetic tunnel junction. We show that the highly [001] textured MgO films contain numerous tilt grain boundaries. First principles calculations reveal how these grain boundaries are associated with locally reduced band gaps (by up to 3 eV). Using a simple model we show how shunting a proportion of the tunnelling current through grain boundaries imposes limits on the maximum magnetoresistance that can be achieved in devices.
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Affiliation(s)
- Jonathan J. Bean
- Department of Physics, University of York, Heslington, York, North Yorkshire, YO10 5DD,UK
| | - Mitsuhiro Saito
- Institute of Engineering Innovation, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan
- Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Shunsuke Fukami
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
- Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
- Center for Innovative Integrated Electronic Systems, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
- Center for Spintronics Research Network, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Hideo Sato
- Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
- Center for Innovative Integrated Electronic Systems, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
- Center for Spintronics Research Network, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Shoji Ikeda
- Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
- Center for Innovative Integrated Electronic Systems, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
- Center for Spintronics Research Network, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Hideo Ohno
- Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
- Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
- Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
- Center for Innovative Integrated Electronic Systems, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai 980-0845, Japan
- Center for Spintronics Research Network, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Yuichi Ikuhara
- Institute of Engineering Innovation, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan
- Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Keith P. McKenna
- Department of Physics, University of York, Heslington, York, North Yorkshire, YO10 5DD,UK
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13
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Kubyshkina E, Unge M, Jonsson BLG. Communication: Band bending at the interface in polyethylene-MgO nanocomposite dielectric. J Chem Phys 2017; 146:051101. [DOI: 10.1063/1.4975318] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Elena Kubyshkina
- School of Electrical Engineering, Electromagnetic Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - Mikael Unge
- ABB Corporate Research, SE 72178 Västerås, Sweden
| | - B. L. G. Jonsson
- School of Electrical Engineering, Electromagnetic Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
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14
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Hoff B, Henry CR, Barth C. Charging C60 islands with the AFM tip. NANOSCALE 2016; 8:411-419. [PMID: 26617348 DOI: 10.1039/c5nr04541j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We show that electrons can be transferred on demand from an AFM tip into single bulk-like C60 islands, which are supported on the insulating NaCl(001) surface. We exemplify this by controlled charge-manipulation experiments conducted in ultrahigh vacuum by noncontact AFM (nc-AFM), electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KPFM). KPFM shows a homogeneous contrast at the islands, which is a signature for an equal distribution of the electrons in the T1u band. The charge dissipates during half a day due to an interaction of the charged C60 islands with defects in the near surface region of NaCl. Our results open the perspective in photo-voltaics to study charge attachment, stability and charge exchange with the environment of any C60 bulk-like system.
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Affiliation(s)
- Brice Hoff
- CNRS, Aix-Marseille University, CINaM UMR 7325, Campus de Luminy, Case 913, 13288 Marseille Cedex 09, France.
| | - Claude R Henry
- CNRS, Aix-Marseille University, CINaM UMR 7325, Campus de Luminy, Case 913, 13288 Marseille Cedex 09, France.
| | - Clemens Barth
- CNRS, Aix-Marseille University, CINaM UMR 7325, Campus de Luminy, Case 913, 13288 Marseille Cedex 09, France.
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15
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Nilius N. Exploring routes to tailor the physical and chemical properties of oxides via doping: an STM study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:303001. [PMID: 26151239 DOI: 10.1088/0953-8984/27/30/303001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Doping opens fascinating possibilities for tailoring the electronic, optical, magnetic, and chemical properties of oxides. The dopants perturb the intrinsic behavior of the material by generating charge centers for electron transfer into adsorbates, by inducing new energy levels for electronic and optical excitations, and by altering the surface morphology and hence the adsorption and reactivity pattern. Despite a vivid scientific interest, knowledge on doped oxides is limited when compared to semiconductors, which reflects the higher complexity and the insulating nature of many oxides. In fact, atomic-scale studies, aiming at a mechanistic understanding of dopant-related processes, are still scarce.In this article, we review our scanning tunneling microscopy (STM) experiments on thin, crystalline oxide films with a defined doping level. We demonstrate how the impurities alter the surface morphology and produce cationic/anionic vacancies in order to keep the system charge neutral. We discuss how individual dopants can be visualized in the lattice, even if they reside in subsurface layers. By means of STM-conductance and x-ray photoelectron spectroscopy, we determine the electronic impact of dopants, including the energies of their eigen states and local band-bending effects in the host oxide. Electronic transitions between dopant-induced gap states give rise to new optical modes, as detected with STM luminescence spectroscopy. From a chemical perspective, dopants are introduced to improve the redox potential of oxide materials. Electron transfer from Mo-donors, for example, alters the growth behavior of gold and activates O2 molecules on a wide-gap CaO surface. Such results demonstrate the enormous potential of doped oxides in heterogeneous catalysis. Our experiments address the issue of doping from a fundamental viewpoint, posing questions on the lattice position, charge state, and electron-transfer potential of the impurity ions. Whether doped oxides are suitable to catalyze surface reactions needs to be explored in more applied studies in the future.
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Affiliation(s)
- Niklas Nilius
- University of Oldenburg, Institute of Physics, Carl v. Ossietzky Str. 9-11, D-26111 Oldenburg, Germany
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16
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Abstract
Nonreducible oxides are characterized by large band gaps and are therefore unable to exchange electrons or to form bonds with surface species, explaining their chemical inertness. The insertion of aliovalent dopants alters this situation, as new electronic states become available in the gap that may be involved in charge-transfer processes. Consequently, the adsorption and reactivity pattern of doped oxides changes with respect to their nondoped counterparts. This Account describes scanning tunneling microscopy (STM) and photoelectron spectroscopy (XPS) experiments that demonstrate the impact of dopants on the physical and chemical properties of well-defined crystalline oxide films. For this purpose, MgO and CaO as archetypical rocksalt oxides have been loaded either with high-valence (Mo, Cr) or low-valence dopants (Li). While the former generate filled states in the oxide band gap and serve as electron donors, the latter produce valence-band holes and give rise to an acceptor response. The dopant-related electronic states and their polarization effect on the surrounding host material are explored with XPS and STM spectroscopy on nonlocal and local scales. Moreover, charge-compensating defects were found to develop in the oxide lattice, such as Ca and O vacancies in Mo- and Li-doped CaO films, respectively. These native defects are able to trap the excess charges of the impurities and therefore diminish the desired doping effect. If noncompensated dopants reside in the host lattice, electron exchange with surface species is observed. Mo ions in CaO, for example, were found to donate electrons to surface Au atoms. The anionic Au strongly binds to the CaO surface and nucleates in the form of monolayer islands, in contrast to the 3D growth prevailing on pristine oxides. Charge transfer is also revealed for surface O2 that traps one Mo electron by forming a superoxo-species. The activated oxygen is characterized by a reinforced binding to the surface, an elongated O-O bond length, and a reduced barrier for dissociation, and represents an important intermediate for oxidation reactions. The charge-transfer processes described here are quenched if Li is inserted into the oxide lattice, neutralizing the effect of the extra electrons. The specific behavior of doped oxides has been explored on a mechanistic level, i.e. on thin-film model systems at ultrahigh vacuum and low temperature. We believe, however, that our results are transferrable to realistic conditions and doping might thus develop into a powerful method to improve the performance of nonreducible oxides in surface-catalyzed reactions.
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Affiliation(s)
- Niklas Nilius
- Carl von Ossietzky University, Department of
Physics, 26111 Oldenburg, Germany
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17
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Wen-Jian Kuang, Qing Li, Jiang-Yong Pan, Xiang Liu, Dong-Ping Li, Jing Chen, Tolner H. Optical Properties of Ultraviolet Quantum Dot Light-Emitting Devices Using ZnO-Cores With a MgO-Shell. ACTA ACUST UNITED AC 2015. [DOI: 10.1109/jdt.2015.2397472] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Li J, Lv S, Chen C, Huang S, Wang Z. Interfacial defect complex at the MgO/SrTiO3heterojunction and its electronic impact. RSC Adv 2014. [DOI: 10.1039/c4ra08961h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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20
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Suich DE, Caplins BW, Shearer AJ, Harris CB. Femtosecond Trapping of Free Electrons in Ultrathin Films of NaCl on Ag(100). J Phys Chem Lett 2014; 5:3073-3077. [PMID: 26278263 DOI: 10.1021/jz501572z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report the excited-state electron dynamics for ultrathin films of NaCl on Ag(100). The first three image potential states (IPSs) were initially observed following excitation. The electrons in the spatially delocalized n = 1 IPS decayed on the ultrafast time scale into multiple spatially localized states lower in energy. The localized electronic states are proposed to correspond to electrons trapped at defects in the NaCl islands. Coverage and temperature dependence of the localized states support the assignment to surface trap states existing at the NaCl/vacuum interface. These results highlight the importance of electron trapping in ultrathin insulating layers.
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Affiliation(s)
- David E Suich
- Department of Chemistry, University of California at Berkeley, 419 Latimer Hall, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, California 94720, United States
| | - Benjamin W Caplins
- Department of Chemistry, University of California at Berkeley, 419 Latimer Hall, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, California 94720, United States
| | - Alex J Shearer
- Department of Chemistry, University of California at Berkeley, 419 Latimer Hall, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, California 94720, United States
| | - Charles B Harris
- Department of Chemistry, University of California at Berkeley, 419 Latimer Hall, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, California 94720, United States
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21
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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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22
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Polymorphism of dislocation core structures at the atomic scale. Nat Commun 2014; 5:3239. [DOI: 10.1038/ncomms4239] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 01/10/2014] [Indexed: 11/08/2022] Open
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23
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Marinopoulos AG. First-principles study of hydrogen configurations at the core of a high-angle grain boundary in cubic yttria-stabilized zirconia. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:025502. [PMID: 24305678 DOI: 10.1088/0953-8984/26/2/025502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Hydrogen is a common impurity in oxides and has been studied extensively by first-principles electronic structure methods. From the calculated charge-transition levels and their position with respect to the conduction-band edge, definitive conclusions can be drawn concerning the electrical activity of hydrogen either as an isolated defect or as part of a defect complex with intrinsic defects of the host lattice. For those oxides such as yttria-stabilized zirconia, which in many cases are used in polycrystalline or nanocrystalline forms, the interaction of hydrogen with grain boundaries needs to be better understood. Using both density-functional theory in the generalized-gradient approximation and a hybrid-functional approach, the present study reports on the types of isolated hydrogen configuration that can be stabilized at the core of the Σ5(310) tilt grain boundary, an interface whose atomistic structure has been determined in good detail by Z-contrast transmission electron microscopy. Initially, the present calculations elucidated the major relaxation modes that lead to low-energy structures for this boundary. Hydrogen exhibited dual behavior by binding to oxygen ions in bond-type OH(-) configurations in its positively charged state, H(+), whereas the negative H(-) species occupied preferably interstitial positions in the available empty space of the grain-boundary core regions. The neutral paramagnetic state, H(0), detected recently in muonium-based spectroscopic studies, was found to be stable in two different configurations: a deep-donor bond-type and a higher-energy quasiatomic interstitial. These configurations are characterized in terms of the trapping character of their excess electron, the spatial localization of the spin density and the resulting hyperfine parameters.
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Affiliation(s)
- A G Marinopoulos
- CEMDRX and Physics Department, University of Coimbra, Rua Larga 3004-516 Coimbra, Portugal
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24
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Yurdakal S, Augugliaro V, Sanz J, Soria J, Sobrados I, Torralvo MJ. The influence of the anatase nanoparticles boundaries on the titania activity performance. J Catal 2014. [DOI: 10.1016/j.jcat.2013.09.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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25
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Cui Y, Shao X, Prada S, Giordano L, Pacchioni G, Freund HJ, Nilius N. Surface defects and their impact on the electronic structure of Mo-doped CaO films: an STM and DFT study. Phys Chem Chem Phys 2014; 16:12764-72. [DOI: 10.1039/c4cp01565g] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Scanning tunneling microscopy and DFT calculations are used to probe the local electronic structure of a Mo-doped CaO film.
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Affiliation(s)
- Yi Cui
- Fritz-Haber-Institut der Max-Planck-Gesellschaft
- D-14195 Berlin, Germany
| | - Xiang Shao
- Fritz-Haber-Institut der Max-Planck-Gesellschaft
- D-14195 Berlin, Germany
| | - Stefano Prada
- Dipartimento di Scienza dei Materiali
- Università di Milano-Bicocca
- 20125 Milano, Italy
| | - Livia Giordano
- Dipartimento di Scienza dei Materiali
- Università di Milano-Bicocca
- 20125 Milano, Italy
| | - Gianfranco Pacchioni
- Dipartimento di Scienza dei Materiali
- Università di Milano-Bicocca
- 20125 Milano, Italy
| | | | - Niklas Nilius
- Fritz-Haber-Institut der Max-Planck-Gesellschaft
- D-14195 Berlin, Germany
- Institut für Physik
- Carl von Ossietzky Universität Oldenburg
- D-26111 Oldenburg, Germany
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26
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Lee W, Kahya O, Toh CT, Ozyilmaz B, Ahn JH. Flexible graphene-PZT ferroelectric nonvolatile memory. NANOTECHNOLOGY 2013; 24:475202. [PMID: 24192319 DOI: 10.1088/0957-4484/24/47/475202] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We report the fabrication of a flexible graphene-based nonvolatile memory device using Pb(Zr0.35,Ti0.65)O3 (PZT) as the ferroelectric material. The graphene and PZT ferroelectric layers were deposited using chemical vapor deposition and sol–gel methods, respectively. Such PZT films show a high remnant polarization (Pr) of 30 μC cm−2 and a coercive voltage (Vc) of 3.5 V under a voltage loop over ±11 V. The graphene–PZT ferroelectric nonvolatile memory on a plastic substrate displayed an on/off current ratio of 6.7, a memory window of 6 V and reliable operation. In addition, the device showed one order of magnitude lower operation voltage range than organic-based ferroelectric nonvolatile memory after removing the anti-ferroelectric behavior incorporating an electrolyte solution. The devices showed robust operation in bent states of bending radii up to 9 mm and in cycling tests of 200 times. The devices exhibited remarkable mechanical properties and were readily integrated with plastic substrates for the production of flexible circuits.
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27
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Uberuaga BP, Bai XM, Dholabhai PP, Moore N, Duffy DM. Point defect-grain boundary interactions in MgO: an atomistic study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:355001. [PMID: 23860398 DOI: 10.1088/0953-8984/25/35/355001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The way in which point defects interact with grain boundaries in oxides is important for understanding radiation damage evolution, sintering, and many other technologically important applications. Here, we examine how vacancies interact with three different grain boundaries in MgO, chosen as a model oxide ceramic. Further, we compare the vacancy interaction with both pristine (as constructed) and 'damaged' boundaries, in which excess interstitials are placed in the boundary plane to mimic the structure after a damage event. We find that the excess interstitials significantly change the interaction of the vacancies with the boundaries and that this change is sensitive to the atomic structure of the boundary. We further observe that complex electrostatic effects arise that can dominate the interaction. These results show that, as boundaries absorb defects, their interaction with other defects will change dramatically.
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Affiliation(s)
- Blas Pedro Uberuaga
- Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
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28
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Vingurt D, Fuks D, Landau MV, Vidruk R, Herskowitz M. Grain boundaries at the surface of consolidated MgO nanocrystals and acid–base functionality. Phys Chem Chem Phys 2013; 15:14783-96. [DOI: 10.1039/c3cp51086g] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Pacchioni G. Electronic interactions and charge transfers of metal atoms and clusters on oxide surfaces. Phys Chem Chem Phys 2013; 15:1737-57. [DOI: 10.1039/c2cp43731g] [Citation(s) in RCA: 175] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Pacchioni G, Freund H. Electron Transfer at Oxide Surfaces. The MgO Paradigm: from Defects to Ultrathin Films. Chem Rev 2012; 113:4035-72. [DOI: 10.1021/cr3002017] [Citation(s) in RCA: 241] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Gianfranco Pacchioni
- Dipartimento di Scienza dei
Materiali, Università di Milano-Bicocca, Via R. Cozzi, 53−20125,
Milano, Italy
| | - Hajo Freund
- Fritz-Haber-Insitut
der MPG,
Department of Chemical Physics, Faradayweg 4-6, 14195 Berlin, Germany
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32
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Liu K, Sakurai M, Aono M. Controlling semiconducting and insulating states of SnO2 reversibly by stress and voltage. ACS NANO 2012; 6:7209-7215. [PMID: 22783968 DOI: 10.1021/nn302312v] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
By applying mechanical stress (by bending a flexible substrate) and an appropriate voltage, the conductance of a single-crystal SnO(2) microrod on a flexible substrate can be tuned in a reversible and nonvolatile manner. The creation and elimination of lattice defects controlled by strain and electrical healing is the origin of this novel transition. A SnO(2) microrod changes continually from its normal semiconducting state to an insulating state by bending the flexible substrate. The insulating state is maintained even after straightening the substrate. Interestingly, by applying an appropriate voltage, the defects are electrically healed and the insulating state reverts to the original semiconducting state. The structural changes in the SnO(2) microrod observed in the Raman spectra are consistent with the nonvolatile property of the transport. This flexible SnO(2) device with the reversible and nonvolatile modification of electrical properties is expected to lead to a better understanding of the mechanism of defect creation and elimination and has potential application in novel flexible strain sensors and switches.
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Affiliation(s)
- Kewei Liu
- International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Tsukuba 305-0044, Japan.
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33
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Stavale F, Shao X, Nilius N, Freund HJ, Prada S, Giordano L, Pacchioni G. Donor Characteristics of Transition-Metal-Doped Oxides: Cr-Doped MgO versus Mo-Doped CaO. J Am Chem Soc 2012; 134:11380-3. [DOI: 10.1021/ja304497n] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Fernando Stavale
- Fritz-Haber-Institut der Max-Planck-Gesellschaft,
Faradayweg 4-6, D-14195 Berlin, Germany
| | - Xiang Shao
- Fritz-Haber-Institut der Max-Planck-Gesellschaft,
Faradayweg 4-6, D-14195 Berlin, Germany
| | - Niklas Nilius
- Fritz-Haber-Institut der Max-Planck-Gesellschaft,
Faradayweg 4-6, D-14195 Berlin, Germany
| | - Hans-Joachim Freund
- Fritz-Haber-Institut der Max-Planck-Gesellschaft,
Faradayweg 4-6, D-14195 Berlin, Germany
| | - Stefano Prada
- Dipartimento di Scienza dei
Materiali, Università di Milano-Bicocca, via Cozzi 53, 20125 Milano, Italy
| | - Livia Giordano
- Dipartimento di Scienza dei
Materiali, Università di Milano-Bicocca, via Cozzi 53, 20125 Milano, Italy
| | - Gianfranco Pacchioni
- Dipartimento di Scienza dei
Materiali, Università di Milano-Bicocca, via Cozzi 53, 20125 Milano, Italy
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34
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Nilius N, Kozlov SM, Jerratsch JF, Baron M, Shao X, Viñes F, Shaikhutdinov S, Neyman KM, Freund HJ. Formation of one-dimensional electronic states along the step edges of CeO₂(111). ACS NANO 2012; 6:1126-33. [PMID: 22206297 DOI: 10.1021/nn2036472] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Scanning tunneling microscopy (STM) combined with density functional theory (DFT) are used to analyze the structural and electronic properties of step edges on the surface of CeO(2)(111) films grown on Ru(0001). Depending on the preparation conditions, 211 or 110-oriented steps develop on the surface, which results in the formation of ceria ad-islands with hexagonal or triangular shapes. STM conductance spectroscopy reveals pronounced differences in the electronic properties of the step edges, as reflected in different onset positions of the ceria conduction band. The band shifts are related to the development of distinct edge electronic states that split-off from the ceria conduction band, as shown with DFT calculations. The separation of the edge states from the main band is governed by the atom-coordination and local charge-distribution along the edge, the latter giving rise to the development of electrostatic dipoles. We expect that the observed edge morphologies determine not only the electronic properties but also the adsorption behavior of step edges on the CeO(2)(111) surface.
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Affiliation(s)
- Niklas Nilius
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
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35
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Kubacka A, Fernández-García M, Colón G. Advanced Nanoarchitectures for Solar Photocatalytic Applications. Chem Rev 2011; 112:1555-614. [DOI: 10.1021/cr100454n] [Citation(s) in RCA: 1901] [Impact Index Per Article: 146.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Anna Kubacka
- Instituto de Catálisis y Petroleoquímica, CSIC, C/Marie Curie 2, 28049-Madrid, Spain
| | | | - Gerardo Colón
- Instituto de Ciencia de Materiales de Sevilla, Centro Mixto CSIC-Universidad de Sevilla, C/Américo Vespucio, 49, 41092-Sevilla, Spain
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36
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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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37
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Shao X, Prada S, Giordano L, Pacchioni G, Nilius N, Freund HJ. Einstellung der Gleichgewichtsform metallischer Nanopartikel durch Dotierung des Oxidträgers. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201105355] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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38
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Shao X, Prada S, Giordano L, Pacchioni G, Nilius N, Freund HJ. Tailoring the shape of metal ad-particles by doping the oxide support. Angew Chem Int Ed Engl 2011; 50:11525-7. [PMID: 21990148 DOI: 10.1002/anie.201105355] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Indexed: 11/06/2022]
Affiliation(s)
- Xiang Shao
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
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39
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Teixeira JM, Ventura J, Araujo JP, Sousa JB, Wisniowski P, Cardoso S, Freitas PP. Resonant tunneling through electronic trapping states in thin MgO magnetic junctions. PHYSICAL REVIEW LETTERS 2011; 106:196601. [PMID: 21668184 DOI: 10.1103/physrevlett.106.196601] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Indexed: 05/30/2023]
Abstract
We report an inelastic electron tunneling spectroscopy study on MgO magnetic junctions with thin barriers (0.85-1.35 nm). Inelastic electron tunneling spectroscopy reveals resonant electronic trapping within the barrier for voltages V>0.15 V. These trapping features are associated with defects in the barrier crystalline structure, as confirmed by high-resolution transmission electron microscopy. Such defects are responsible for resonant tunneling due to energy levels that are formed in the barrier. A model was applied to determine the average location and energy level of the traps, indicating that they are mostly located in the middle of the MgO barrier, in accordance with the high-resolution transmission electron microscopy data and trap-assisted tunneling conductance theory. Evidence of the influence of trapping on the voltage dependence of tunnel magnetoresistance is shown.
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Affiliation(s)
- J M Teixeira
- IFIMUP and IN-Institute of Nanoscience and Nanotechnology, and Departamento de Fisica, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal.
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40
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McKenna KP, Koller D, Sternig A, Siedl N, Govind N, Sushko PV, Diwald O. Optical properties of nanocrystal interfaces in compressed MgO nanopowders. ACS NANO 2011; 5:3003-9. [PMID: 21443262 PMCID: PMC3082970 DOI: 10.1021/nn200062d] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The optical properties and charge trapping phenomena observed on oxide nanocrystal ensembles can be strongly influenced by the presence of nanocrystal interfaces. MgO powders represent a convenient system to study these effects due to the well-defined shape and controllable size distributions of MgO nanocrystals. The spectroscopic properties of nanocrystal interfaces are investigated by monitoring the dependence of absorption characteristics on the concentration of the interfaces in the nanopowders. The presence of interfaces is found to affect the absorption spectra of nanopowders more significantly than changing the size of the constituent nanocrystals and, thus, leading to the variation of the relative abundance of light-absorbing surface structures. We find a strong absorption band in the 4.0-5.5 eV energy range, which was previously attributed to surface features of individual nanocrystals, such as corners and edges. These findings are supported by complementary first-principles calculations. The possibility to directly address such interfaces by tuning the energy of excitation may provide new means for functionalization and chemical activation of nanostructures and can help improve performance and reliability for many nanopowder applications.
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Affiliation(s)
- Keith P. McKenna
- WPI-AIMR, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980-8577, Japan
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
- Address correspondence to ;
| | - David Koller
- Institute of Materials Chemistry, Vienna University of Technology, Getreidemarkt 9, 1060 Wien, Austria
| | - Andreas Sternig
- Friedrich-Alexander Universitat, Erlangen-Nurnberg, Cauerstrasse 4, Erlangen D-91058, Germany
| | - Nicolas Siedl
- Institute of Materials Chemistry, Vienna University of Technology, Getreidemarkt 9, 1060 Wien, Austria
- Friedrich-Alexander Universitat, Erlangen-Nurnberg, Cauerstrasse 4, Erlangen D-91058, Germany
| | - Niranjan Govind
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Peter V. Sushko
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Oliver Diwald
- Institute of Materials Chemistry, Vienna University of Technology, Getreidemarkt 9, 1060 Wien, Austria
- Friedrich-Alexander Universitat, Erlangen-Nurnberg, Cauerstrasse 4, Erlangen D-91058, Germany
- Address correspondence to ;
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Sushko PV, Shluger AL, Toda Y, Hirano M, Hosono H. Models of stoichiometric and oxygen-deficient surfaces of subnanoporous 12CaO·7Al
2
O
3. Proc Math Phys Eng Sci 2011. [DOI: 10.1098/rspa.2010.0560] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Surface structures of stoichiometric and oxygen-deficient complex subnanoporous oxide 12CaO·7Al
2
O
3
(C12A7) are generated by simulating lattice rupture under the influence of an external strain. Extra-framework anions are found to serve as buffers, maintaining stability of the lattice cages in both elastic and inelastic stretching regimes. Modification of the local atomic structure in the near-surface region reduces the band gap in stoichiometric insulating C12A7. On the contrary, the band gap appears in the oxygen-deficient form of C12A7, which is metallic in the bulk. This is due to formation of the surface electron traps, which differ both in the type of the local atomic structure and stability of the electronic states. The implications of this electronic structure for the surface chemical and electron emission properties are discussed.
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Affiliation(s)
- Peter V. Sushko
- Department of Physics and Astronomy and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, UK
- WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan
| | - Alexander L. Shluger
- Department of Physics and Astronomy and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, UK
- WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan
| | - Yoshitake Toda
- Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8503, Japan
| | - Masahiro Hirano
- Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8503, Japan
| | - Hideo Hosono
- Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8503, Japan
- Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan
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42
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McKenna KP, Shluger AL. Electron and hole trapping in polycrystalline metal oxide materials. Proc Math Phys Eng Sci 2011. [DOI: 10.1098/rspa.2010.0518] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Electron and hole trapping by grain boundaries and dislocations in polycrystalline materials is important for wide ranging technological applications such as solar cells, microelectronics, photo-catalysts and rechargeable batteries. In this article, we first give an overview of the computational and methodological challenges involved in modelling such effects. This is followed by a discussion of two recent studies we have made on electron/hole trapping in wide gap insulators. The results suggest that such effects can be important for many applications which we discuss. These computationally demanding calculations have made extensive use of both the HPCx and HECToR services.
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Affiliation(s)
- Keith P. McKenna
- World Premier International Research Center, Advanced Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Alexander L. Shluger
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
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43
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Myrach P, Nilius N, Levchenko S, Gonchar A, Risse T, Dinse KP, Boatner L, Frandsen W, Horn R, Freund HJ, Schlögl R, Scheffler M. Temperature-Dependent Morphology, Magnetic and Optical Properties of Li-Doped MgO. ChemCatChem 2010. [DOI: 10.1002/cctc.201000083] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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44
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Stoneham M. The strange magnetism of oxides and carbons. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:074211. [PMID: 21386389 DOI: 10.1088/0953-8984/22/7/074211] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Magnetism is not usually expected in simple sp oxides like MgO or in carbons like graphite. Yet basic intrinsic defects in these systems can be magnetic in ways that seem to be shared by more complex oxides. A second puzzle comes from reports of possible room temperature ferromagnetism in simple oxides, where experiments are not always in agreement. This paper discusses what determines whether point defects like cation vacancies in oxides have magnetic or non-magnetic ground states. It also discusses the possible connections between point defect ground states and oxide ferromagnetism. The connectivity issue raises questions about possible diffuse states in nanocrystalline oxides, several possibilities being outlined. These ideas raise the further possibility that the magnetism might be written in these oxides at the nanoscale, perhaps using atomic force microscopy.
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Affiliation(s)
- Marshall Stoneham
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, WC1E 6BT, UK
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45
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Sternig A, Müller M, McCallum M, Bernardi J, Diwald O. BaO clusters on MgO nanocubes: a quantitative analysis of optical-powder properties. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2010; 6:582-8. [PMID: 20029851 DOI: 10.1002/smll.200901662] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Uniformly sized and shaped nanoparticles are well suited for the quantitative characterization of optical-powder properties. For the first time, quantum yields related to photoluminescence emissions that originate from the photoexcitation of MgO nanocube corners and edges are measured. In addition, the surfaces of these nanoparticles are doped with submonolayer barium, which oxidizes during adsorption onto the MgO nanocrystal surfaces and transforms in O(2) atmosphere into BaO. UV-Vis diffuse reflectance and photoluminescence spectroscopy is employed to explore whether 10(-3) monolayer equivalents of these dopants affect the MgO specific optical properties. Surface-admixed BaO produces additional absorption and photoluminescence emission features but does not significantly affect those specific to MgO nanocubes. On this basis the number of optically active sites that can be sampled inside a powder of alkaline earth oxide nanoparticles using a standard spectrometer system is estimated.
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Affiliation(s)
- Andreas Sternig
- Institute of Materials Chemistry, Vienna University of Technology, Veterinärplatz 1/GA, Vienna 1210, Austria
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46
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Caruana DJ, Holt KB. Astroelectrochemistry: the role of redox reactions in cosmic dust chemistry. Phys Chem Chem Phys 2010; 12:3072-9. [DOI: 10.1039/b917817a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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