1
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Xu W, Shu Y, Xu M, Xie J, Li Y, Dong H. Unexpected electro-catalytic activity of the CO reduction reaction on Cr-embedded poly-phthalocyanine realized by strain engineering: a computational study. Phys Chem Chem Phys 2023; 25:12872-12881. [PMID: 37165891 DOI: 10.1039/d3cp00861d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The electrochemical conversion of carbon monoxide (CO) into value-added products is highly promising for carbon utilization and CO removal. Based on previous theoretical studies, we computationally explored the effect of strain engineering on electrocatalysis of the CO reduction reaction (CORR) by two-dimensional (2D) transition metal embedded polyphthalocyanines (MPPcs). By calculating the adsorption energy of CO and the free energies of key intermediates on the MPPcs under uniaxial and biaxial strains, it was revealed that only CrPPc under biaxial strain has the potential to exhibit significant enhancement of the catalytic performance. The free energy diagrams of the CORR catalyzed by CrPPc were plotted under specific biaxial strains, where both the optimal reaction pathway and rate-determining step are found to be evidently changed. What's more, the 5% compressive strain imposed on CrPPc results in an ultra-low limiting potential (UL = -0.09 V) with high selectivity on CH4 as the final product, indicating unexpected electro-catalytic activity. Our study clearly elucidates that moderate strain could greatly enhance the electrocatalytic performance of 2D materials in the CORR.
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Affiliation(s)
- Wenzhen Xu
- School of Materials Engineering, Changshu Institute of Technology, Changshu, Jiangsu 215500, China.
- College of Materials Science and Engineering, Xi'an Shiyou University, Xi'an, Shaanxi 710065, China
| | - Yunpeng Shu
- School of Materials Engineering, Changshu Institute of Technology, Changshu, Jiangsu 215500, China.
| | - Mengmeng Xu
- School of Materials Engineering, Changshu Institute of Technology, Changshu, Jiangsu 215500, China.
| | - Juan Xie
- School of Materials Engineering, Changshu Institute of Technology, Changshu, Jiangsu 215500, China.
| | - Youyong Li
- Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, China.
| | - Huilong Dong
- School of Materials Engineering, Changshu Institute of Technology, Changshu, Jiangsu 215500, China.
- Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Nankai University, Tianjin 300071, China
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2
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Lee F, Tripathi M, Sanchez Salas R, Ogilvie SP, Amorim Graf A, Jurewicz I, Dalton AB. Localised strain and doping of 2D materials. NANOSCALE 2023; 15:7227-7248. [PMID: 37038962 DOI: 10.1039/d2nr07252a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
There is a growing interest in 2D materials-based devices as the replacement for established materials, such as silicon and metal oxides in microelectronics and sensing, respectively. However, the atomically thin nature of 2D materials makes them susceptible to slight variations caused by their immediate environment, inducing doping and strain, which can vary between, and even microscopically within, devices. One of the misapprehensions for using 2D materials is the consideration of unanimous intrinsic properties over different support surfaces. The interfacial interaction, intrinsic structural disorder and external strain modulate the properties of 2D materials and govern the device performance. The understanding, measurement and control of these factors are thus one of the significant challenges for the adoption of 2D materials in industrial electronics, sensing, and polymer composites. This topical review provides a comprehensive overview of the effect of strain-induced lattice deformation and its relationship with physical and electronic properties. Using the example of graphene and MoS2 (as the prototypical 2D semiconductor), we rationalise the importance of scanning probe techniques and Raman spectroscopy to elucidate strain and doping in 2D materials. These effects can be directly and accurately characterised through Raman shifts in a non-destructive manner. A generalised model has been presented that deconvolutes the intertwined relationship between strain and doping in graphene and MoS2 that could apply to other members of the 2D materials family. The emerging field of straintronics is presented, where the controlled application of strain over 2D materials induces tuneable physical and electronic properties. These perspectives highlight practical considerations for strain engineering and related microelectromechanical applications.
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Affiliation(s)
- Frank Lee
- University of Sussex, Brighton, BN1 9RH, UK.
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3
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Baimova JA, Shcherbinin SA. Metal/Graphene Composites: A Review on the Simulation of Fabrication and Study of Mechanical Properties. MATERIALS (BASEL, SWITZERLAND) 2022; 16:202. [PMID: 36614540 PMCID: PMC9822068 DOI: 10.3390/ma16010202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Revised: 12/19/2022] [Accepted: 12/20/2022] [Indexed: 06/17/2023]
Abstract
Although carbon materials, particularly graphene and carbon nanotubes, are widely used to reinforce metal matrix composites, understanding the fabrication process and connection between morphology and mechanical properties is still not understood well. This review discusses the relevant literature concerning the simulation of graphene/metal composites and their mechanical properties. This review demonstrates the promising role of simulation of composite fabrication and their properties. Further, results from the revised studies suggest that morphology and fabrication techniques play the most crucial roles in property improvements. The presented results can open up the way for developing new nanocomposites based on the combination of metal and graphene components. It is shown that computer simulation is a possible and practical way to understand the effect of the morphology of graphene reinforcement and strengthening mechanisms.
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Affiliation(s)
- Julia A. Baimova
- Institute for Metals Superplasticity Problems of the Russian Academy of Sciences, Ufa 450001, Russia
- Department of Physics and Technology of Nanomaterials, Bashkir State University, Ufa 450076, Russia
| | - Stepan A. Shcherbinin
- Departement of Theoretical and Applied Mechanics, Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya 29, St. Petersburg 195251, Russia
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4
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McClimon JB, Milne Z, Hasz K, Carpick RW. Linescan Lattice Microscopy: A Technique for the Accurate Measurement and Mapping of Lattice Spacing and Strain with Atomic Force Microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:8261-8269. [PMID: 34170699 DOI: 10.1021/acs.langmuir.1c01019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Lateral resolution and accuracy in scanning probe microscopies are limited by the nonideality of piezoelectric scanning elements due to phenomena including nonlinearity, hysteresis, and creep. By taking advantage of the well-established atomic-scale stick-slip phenomenon in contact-mode atomic force microscopy, we have developed a method for simultaneously indexing and measuring the spacing of surface atomic lattices using only Fourier analysis of unidirectional linescan data. The first step of the technique is to calibrate the X-piezo response using the stick-slip behavior itself. This permits lateral calibration to better than 1% error between 2.5 nm and 9 μm, without the use of calibration gratings. Lattice indexing and lattice constant determination are demonstrated in this way on the NaCl(001) crystal surface. After piezo calibration, lattice constant measurement on a natural bulk MoS2(0001) surface is demonstrated with better than 0.2% error. This is used to measure nonuniform thermal mismatch strain for chemical vapor deposition (CVD)-grown monolayer MoS2 as small as 0.5%. A spatial mapping technique for the lattice spacing is developed and demonstrated, with absolute accuracy better than 0.2% and relative accuracy better than 0.1%, within a map of 12.5 × 12.5 nm2 pixels using bulk highly oriented pyrolytic graphite (HOPG) and MoS2 as reference materials.
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Affiliation(s)
- J Brandon McClimon
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Zac Milne
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Kathryn Hasz
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Robert W Carpick
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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5
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Kondrashov I, Komlenok M, Pivovarov P, Savin S, Obraztsova E, Rybin M. Preparation of Copper Surface for the Synthesis of Single-Layer Graphene. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:1071. [PMID: 33921942 PMCID: PMC8143535 DOI: 10.3390/nano11051071] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Revised: 04/13/2021] [Accepted: 04/19/2021] [Indexed: 11/16/2022]
Abstract
Chemical vapor deposition synthesis of graphene on copper foil from methane is the most promising technology for industrial production. However, an important problem of the formation of the additional graphene layers during synthesis arises due to the strong roughness of the initial copper foil. In this paper, various approaches are demonstrated to form a smooth copper surface before graphene synthesis to reduce the amount of few layer graphene islands. Six methods of surface processing of copper foils are studied and the decrease of the roughness from 250 to as low as 80 nm is achieved. The correlation between foil roughness and the formation of the additional layer is demonstrated. Under optimized conditions of surface treatment, the content of the additional graphene layer drops from 9 to 2.1%. The quality and the number of layers of synthesized graphene are analyzed by Raman spectroscopy, scanning electron microscopy and measurements of charge mobility.
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Affiliation(s)
- Ivan Kondrashov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov St., 119991 Moscow, Russia; (M.K.); (P.P.); (E.O.)
| | - Maxim Komlenok
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov St., 119991 Moscow, Russia; (M.K.); (P.P.); (E.O.)
| | - Pavel Pivovarov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov St., 119991 Moscow, Russia; (M.K.); (P.P.); (E.O.)
| | - Sergey Savin
- MIREA—Russian Technological University, 78 Vernadsky Avenue, 119454 Moscow, Russia;
| | - Elena Obraztsova
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov St., 119991 Moscow, Russia; (M.K.); (P.P.); (E.O.)
- Moscow Institute of Physics and Technology, State University, 1 “A” Kerchenskaya St., 117303 Moscow, Russia
| | - Maxim Rybin
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov St., 119991 Moscow, Russia; (M.K.); (P.P.); (E.O.)
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6
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Deng B, Hou Y, Liu Y, Khodkov T, Goossens S, Tang J, Wang Y, Yan R, Du Y, Koppens FHL, Wei X, Zhang Z, Liu Z, Peng H. Growth of Ultraflat Graphene with Greatly Enhanced Mechanical Properties. NANO LETTERS 2020; 20:6798-6806. [PMID: 32787178 DOI: 10.1021/acs.nanolett.0c02785] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Graphene grown on Cu by chemical vapor deposition is rough due to the surface roughening of Cu for releasing interfacial thermal stress and/or graphene bending energy. The roughness degrades the electrical conductance and mechanical strength of graphene. Here, by using vicinal Cu(111) and flat Cu(111) as model substrates, we investigated the critical role of original surface topography on the surface deformation of Cu covered by graphene. We demonstrated that terrace steps on vicinal Cu(111) dominate the formation of step bunches (SBs). Atomically flat graphene with roughness down to 0.2 nm was grown on flat Cu(111) films. When SB-induced ripples were avoided, as-grown ultraflat graphene maintained its flat feature after transfer. The ultraflat graphene exhibited extraordinary mechanical properties with Young's modulus ≈ 940 GPa and strength ≈ 117 GPa, comparable to mechanical exfoliated ones. Molecular dynamics simulation revealed the mechanism of softened elastic response and weakened strength of graphene with rippled structures.
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Affiliation(s)
- Bing Deng
- Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Yuan Hou
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Ying Liu
- State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China
- Beijing Innovation Center for Engineering Science and Advanced Technology, Peking University, Beijing 100871, China
| | - Tymofiy Khodkov
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona 08860, Spain
| | - Stijin Goossens
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona 08860, Spain
| | - Jilin Tang
- Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Yani Wang
- Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Rui Yan
- Beijing Graphene Institute (BGI), Beijing 100094, China
| | - Yin Du
- Beijing Graphene Institute (BGI), Beijing 100094, China
| | - Frank H L Koppens
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona 08860, Spain
- ICREA Institució Catalana de Recerca i Estudis Avançats, Barcelona 08010, Spain
| | - Xiaoding Wei
- State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China
- Beijing Innovation Center for Engineering Science and Advanced Technology, Peking University, Beijing 100871, China
| | - Zhong Zhang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China
| | - Zhongfan Liu
- Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
- Beijing Graphene Institute (BGI), Beijing 100094, China
| | - Hailin Peng
- Center for Nanochemistry (CNC), Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences (BNLMS), College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
- Beijing Graphene Institute (BGI), Beijing 100094, China
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7
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Park J, Oh I, Jin MJ, Jo J, Choe D, Yun HD, Lee SW, Lee Z, Kwon SY, Jin H, Chung SB, Yoo JW. Observation of spin-polarized Anderson state around charge neutral point in graphene with Fe-clusters. Sci Rep 2020; 10:4784. [PMID: 32179819 PMCID: PMC7076017 DOI: 10.1038/s41598-020-61481-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Accepted: 02/17/2020] [Indexed: 11/09/2022] Open
Abstract
The pristine graphene described with massless Dirac fermion could bear topological insulator state and ferromagnetism via the band structure engineering with various adatoms and proximity effects from heterostructures. In particular, topological Anderson insulator state was theoretically predicted in tight-binding honeycomb lattice with Anderson disorder term. Here, we introduced physi-absorbed Fe-clusters/adatoms on graphene to impose exchange interaction and random lattice disorder, and we observed Anderson insulator state accompanying with Kondo effect and field-induced conducting state upon applying the magnetic field at around a charge neutral point. Furthermore, the emergence of the double peak of resistivity at ν = 0 state indicates spin-splitted edge state with high effective exchange field (>70 T). These phenomena suggest the appearance of topological Anderson insulator state triggered by the induced exchange field and disorder.
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Affiliation(s)
- Jungmin Park
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
- Center for Scientific Instrumentation, Division of Scientific Instrumentation & Management, Korea Basic Science Institute, Daejeon, 34133, Korea
| | - Inseon Oh
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Mi-Jin Jin
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Junhyeon Jo
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Daeseong Choe
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Hyung Duk Yun
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Suk Woo Lee
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
- Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Zonghoon Lee
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
- Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Soon-Yong Kwon
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Hosub Jin
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan, 44919, Korea
| | - Suk Bum Chung
- Department of Physics, University of Seoul, Seoul, 02504, Korea
| | - Jung-Woo Yoo
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea.
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8
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Belyaeva LA, Jiang L, Soleimani A, Methorst J, Risselada HJ, Schneider GF. Liquids relax and unify strain in graphene. Nat Commun 2020; 11:898. [PMID: 32060270 PMCID: PMC7021765 DOI: 10.1038/s41467-020-14637-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 01/17/2020] [Indexed: 12/05/2022] Open
Abstract
Solid substrates often induce non-uniform strain and doping in graphene monolayer, therefore altering the intrinsic properties of graphene, reducing its charge carrier mobilities and, consequently, the overall electrical performance. Here, we exploit confocal Raman spectroscopy to study graphene directly free-floating on the surface of water, and show that liquid supports relief the preexisting strain, have negligible doping effect and restore the uniformity of the properties throughout the graphene sheet. Such an effect originates from the structural adaptability and flexibility, lesser contamination and weaker intermolecular bonding of liquids compared to solid supports, independently of the chemical nature of the liquid. Moreover, we demonstrate that water provides a platform to study and distinguish chemical defects from substrate-induced defects, in the particular case of hydrogenated graphene. Liquid supports, thus, are advantageous over solid supports for a range of applications, particularly for monitoring changes in the graphene structure upon chemical modification. Here, the authors report water as a superior platform to suspend graphene compared to solid substrates that induce non-uniformity and do not provide structural flexibility. They utilize confocal Raman spectroscopy to study graphene floating freely on the surface of water to show that a liquid support relieves the pre-existing strain.
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Affiliation(s)
- Liubov A Belyaeva
- Faculty of Science, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| | - Lin Jiang
- Faculty of Science, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| | - Alireza Soleimani
- Institute of Theoretical Physics, Georg-August University Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Jeroen Methorst
- Faculty of Science, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| | - H Jelger Risselada
- Faculty of Science, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC, Leiden, The Netherlands.,Institute of Theoretical Physics, Georg-August University Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Grégory F Schneider
- Faculty of Science, Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC, Leiden, The Netherlands.
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9
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Zhang J, Lin L, Jia K, Sun L, Peng H, Liu Z. Controlled Growth of Single-Crystal Graphene Films. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1903266. [PMID: 31583792 DOI: 10.1002/adma.201903266] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 07/23/2019] [Indexed: 06/10/2023]
Abstract
Grain boundaries produced during material synthesis affect both the intrinsic properties of materials and their potential for high-end applications. This effect is commonly observed in graphene film grown using chemical vapor deposition and therefore caused intense interest in controlled growth of grain-boundary-free graphene single crystals in the past ten years. The main methods for enlarging graphene domain size and reducing graphene grain boundary density are classified into single-seed and multiseed approaches, wherein reduction of nucleation density and alignment of nucleation orientation are respectively realized in the nucleation stage. On this basis, detailed synthesis strategies, corresponding mechanisms, and key parameters in the representative methods of these two approaches are separately reviewed, with the aim of providing comprehensive knowledge and a snapshot of the latest status of controlled growth of single-crystal graphene films. Finally, perspectives on opportunities and challenges in synthesizing large-area single-crystal graphene films are discussed.
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Affiliation(s)
- Jincan Zhang
- Center for Nanochemistry, Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, P. R. China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, P. R. China
| | - Li Lin
- Center for Nanochemistry, Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, P. R. China
| | - Kaicheng Jia
- Center for Nanochemistry, Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, P. R. China
| | - Luzhao Sun
- Center for Nanochemistry, Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, P. R. China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, P. R. China
| | - Hailin Peng
- Center for Nanochemistry, Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, P. R. China
- Beijing Graphene Institute, Beijing, 100095, P. R. China
| | - Zhongfan Liu
- Center for Nanochemistry, Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, P. R. China
- Beijing Graphene Institute, Beijing, 100095, P. R. China
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10
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Wu Z, Zhang X, Das A, Liu J, Zou Z, Zhang Z, Xia Y, Zhao P, Wang H. Step-by-step monitoring of CVD-graphene during wet transfer by Raman spectroscopy. RSC Adv 2019; 9:41447-41452. [PMID: 35541595 PMCID: PMC9076457 DOI: 10.1039/c9ra09268d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 12/08/2019] [Indexed: 11/26/2022] Open
Abstract
Transfer acts as a crucial bridge between the chemical vapor deposition (CVD) synthesis of large-scale graphene and its applications, but the quality evolution of a graphene film during transfer remains unclear. Here we use scanning Raman spectroscopy to monitor as-grown graphene during each step of wet transfer including floating on etchant solution, loaded onto a target substrate, and with additional annealing. Results show that the etchant solution results in strong compressive strain and p-type doping to floating graphene, but both are significantly reduced after the sample is loaded and rinsed especially for the doping. An annealing treatment increases the compressive strain in graphene but hardly its doping level. Moreover, when a poly(methyl methacrylate) (PMMA) layer is used to assist the transfer, it does not only increase the p-type doping of floating graphene but also lowers the crystalline quality of annealed graphene. Therefore, to obtain graphene with better quality, besides the attempts of improving CVD synthesis for its larger domain sizes, universal and easy-to-use polymer-free transfer techniques must be developed as well. The quality evolution of as-grown graphene during wet transfer from Cu to SiO2/Si substrate is investigated by Raman spectroscopy and the relavant factors during this process are identified.![]()
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Affiliation(s)
- Zehao Wu
- Center for X-Mechanics and Institute of Applied Mechanics, Zhejiang University Hangzhou 310012 P. R. China
| | - Xuewei Zhang
- Center for X-Mechanics and Institute of Applied Mechanics, Zhejiang University Hangzhou 310012 P. R. China
| | - Atanu Das
- Center for X-Mechanics and Institute of Applied Mechanics, Zhejiang University Hangzhou 310012 P. R. China
| | - Jinglan Liu
- Center for X-Mechanics and Institute of Applied Mechanics, Zhejiang University Hangzhou 310012 P. R. China
| | - Zhenxing Zou
- Center for X-Mechanics and Institute of Applied Mechanics, Zhejiang University Hangzhou 310012 P. R. China
| | - Zilong Zhang
- Center for X-Mechanics and Institute of Applied Mechanics, Zhejiang University Hangzhou 310012 P. R. China
| | - Yang Xia
- Institute of Microelectronics, Chinese Academy of Sciences Beijing 100029 China
| | - Pei Zhao
- Center for X-Mechanics and Institute of Applied Mechanics, Zhejiang University Hangzhou 310012 P. R. China
| | - Hongtao Wang
- Center for X-Mechanics and Institute of Applied Mechanics, Zhejiang University Hangzhou 310012 P. R. China
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11
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Schmidt N, Li J, Gottardi S, Moreno-Lopez JC, Enache M, Monjas L, van der Vlag R, Havenith RWA, Hirsch AKH, Stöhr M. Comparing the Self-Assembly of Sexiphenyl-Dicarbonitrile on Graphite and Graphene on Cu(111). Chemistry 2019; 25:5065-5070. [PMID: 30657213 PMCID: PMC6519158 DOI: 10.1002/chem.201806312] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Indexed: 12/04/2022]
Abstract
A comparative study on the self‐assembly of sexiphenyl‐dicarbonitrile on highly oriented pyrolytic graphite and single‐layer graphene on Cu(111) is presented. Despite an overall low molecule–substrate interaction, the close‐packed structures exhibit a peculiar shift repeating every four to five molecules. This shift has hitherto not been reported for similar systems and is hence a unique feature induced by the graphitic substrates.
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Affiliation(s)
- Nico Schmidt
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands
| | - Jun Li
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands
| | - Stefano Gottardi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands
| | - Juan Carlos Moreno-Lopez
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.,Current affiliation: Faculty of Physics, University of Vienna, Strudlhofgasse 4, 1090, Vienna, Austria
| | - Mihaela Enache
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands
| | - Leticia Monjas
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 7, 9747, AG, Groningen, The Netherlands
| | - Ramon van der Vlag
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 7, 9747, AG, Groningen, The Netherlands
| | - Remco W A Havenith
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.,Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 7, 9747, AG, Groningen, The Netherlands.,Ghent Quantum Chemistry Group, Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281 (S3), 9000, Ghent, Belgium
| | - Anna K H Hirsch
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 7, 9747, AG, Groningen, The Netherlands.,Department of Drug Design and Optimization (DDOP), Helmholtz Institute for Pharmaceutical Research Saarland, 66123, Saarbrücken, Germany.,Department of Pharmacy, Saarland University, Campus Building E8.1, 66123, Saarbrücken, Germany
| | - Meike Stöhr
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands
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12
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Wang K, Ouyang W, Cao W, Ma M, Zheng Q. Robust superlubricity by strain engineering. NANOSCALE 2019; 11:2186-2193. [PMID: 30671572 DOI: 10.1039/c8nr07963c] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Structural superlubricity, a nearly frictionless state between two contact solid surfaces, has attracted rapidly increasing attention during the past few years. Yet a key problem that limits its promising applications is the high anisotropy of friction which always leads to its failure. Here we study the friction of a graphene flake sliding on top of a graphene substrate using molecular dynamics simulation. The results show that by applying strain on the substrate, biaxial stretching is better than uniaxial stretching in terms of reducing interlayer friction. Importantly, we find that robust superlubricity can be achieved via both biaxial and uniaxial stretching, namely for stretching above a critical strain which has been achieved experimentally, the friction is no longer dependent on the relative orientation mainly due to the complete lattice mismatch. The underlying mechanism is revealed to be the Moiré pattern formed. These findings provide a viable approach for the realization of robust superlubricity through strain engineering.
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Affiliation(s)
- Kunqi Wang
- State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China. and Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China.
| | - Wengen Ouyang
- Department of Physical Chemistry, School of Chemistry, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Wei Cao
- State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China. and Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China.
| | - Ming Ma
- State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China. and Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China.
| | - Quanshui Zheng
- Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China. and Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
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13
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Anagnostopoulos G, Sygellou L, Paterakis G, Polyzos I, Aggelopoulos CA, Galiotis C. Enhancing the adhesion of graphene to polymer substrates by controlled defect formation. NANOTECHNOLOGY 2019; 30:015704. [PMID: 30362463 DOI: 10.1088/1361-6528/aae683] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The mechanical integrity of composite materials depends primarily on the interface strength and the defect density of the reinforcement which is the provider of enhanced strength and stiffness. In the case of graphene/polymer nanocomposites which are characterized by an extremely large interface region, any defects in the inclusion (such as folds, cracks, holes, etc) will have a detrimental effect to the internal strain distribution and the resulting mechanical performance. This conventional wisdom, however, can be challenged if the defect size is reduced beyond the critical size for crack formation to the level of atomic vacancies. In that case, there should be no practical effect on crack propagation and depending on the nature of the vacancies the interface strength may in fact increase. In this work we employed argon ion (Ar+) bombardment and subsequent exposure to hydrogen (H2) to induce (as revealed by x-ray and ultraviolet photoelectron spectroscopy and Raman spectroscopy) passivated atomic single vacancies to CVD graphene. The modified graphene was subsequently transferred to PMMA bars and the morphology, wettability and the interface adhesion of the CVD graphene/PMMA system were investigated with atomic force microscopy technique and Raman analysis. The results obtained showed clearly an overall improved mechanical behavior of graphene/polymer interface, since an increase as well as a more uniform shift distribution with strain is observed. This paves the way for interface engineering in graphene/polymer systems which, in pristine condition, suffer from premature graphene slippage and subsequent failure.
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Affiliation(s)
- George Anagnostopoulos
- Institute of Chemical Engineering Sciences, Foundation for Research and Technology-Hellas (FORTH/ICE-HT), Patras 265 04, Greece
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14
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Anagnostopoulos G, Paterakis G, Polyzos I, Pappas PN, Kouroupis-Agalou K, Mirotta N, Scidà A, Palermo V, Parthenios J, Papagelis K, Galiotis C. Strain Engineering in Highly Wrinkled CVD Graphene/Epoxy Systems. ACS APPLIED MATERIALS & INTERFACES 2018; 10:43192-43202. [PMID: 30406999 DOI: 10.1021/acsami.8b14698] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Chemical vapor deposition (CVD) is regarded as a promising fabrication method for the automated, large-scale, production of graphene and other two-dimensional materials. However, its full commercial exploitation is limited by the presence of structural imperfections such as folds, wrinkles, and even cracks that downgrade its physical and mechanical properties. For example, as shown here by means of Raman spectroscopy, the stress transfer from an epoxy matrix to CVD graphene is on average 30% of that of exfoliated monolayer graphene of over 10 μm in dimensions. However, in terms of electrical response, the situation is reversed; the resistance has been found here to decrease by the imposition of mechanical deformation possibly due to the opening up of the structure and the associated increase of electron mobility. This finding paves the way for employing CVD graphene/epoxy composites or coatings as conductive "networks" or bridges in cases for which the conductivity needs to be increased or at least retained when the system is under deformation. The tuning/control of such systems and their operative limitations are discussed here.
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Affiliation(s)
- George Anagnostopoulos
- Institute of Chemical Engineering Sciences, Foundation for Research and Technology-Hellas (FORTH/ ICE-HT) , Patras 265 04 , Greece
| | - George Paterakis
- Institute of Chemical Engineering Sciences, Foundation for Research and Technology-Hellas (FORTH/ ICE-HT) , Patras 265 04 , Greece
| | - Ioannis Polyzos
- Institute of Chemical Engineering Sciences, Foundation for Research and Technology-Hellas (FORTH/ ICE-HT) , Patras 265 04 , Greece
| | - Panagiotis-Nektarios Pappas
- Institute of Chemical Engineering Sciences, Foundation for Research and Technology-Hellas (FORTH/ ICE-HT) , Patras 265 04 , Greece
| | - Kostantinos Kouroupis-Agalou
- ISOF-Istituto per la Sintesi Organica e la Fotoreattivita-Consiglio Nazionale delle Ricerche , via Gobetti 101 , 40129 Bologna , Italy
| | - Nicola Mirotta
- ISOF-Istituto per la Sintesi Organica e la Fotoreattivita-Consiglio Nazionale delle Ricerche , via Gobetti 101 , 40129 Bologna , Italy
| | - Alessandra Scidà
- ISOF-Istituto per la Sintesi Organica e la Fotoreattivita-Consiglio Nazionale delle Ricerche , via Gobetti 101 , 40129 Bologna , Italy
| | - Vincenzo Palermo
- ISOF-Istituto per la Sintesi Organica e la Fotoreattivita-Consiglio Nazionale delle Ricerche , via Gobetti 101 , 40129 Bologna , Italy
- Department of Industrial and Materials Science , Chalmers University of Technology , SE-412 96 Gothenburg , Sweden
| | - John Parthenios
- Institute of Chemical Engineering Sciences, Foundation for Research and Technology-Hellas (FORTH/ ICE-HT) , Patras 265 04 , Greece
| | - Konstantinos Papagelis
- Institute of Chemical Engineering Sciences, Foundation for Research and Technology-Hellas (FORTH/ ICE-HT) , Patras 265 04 , Greece
- Department of Solid State Physics, School of Physics , Aristotle University of Thessaloniki , Thessaloniki 54124 , Greece
| | - Costas Galiotis
- Institute of Chemical Engineering Sciences, Foundation for Research and Technology-Hellas (FORTH/ ICE-HT) , Patras 265 04 , Greece
- Department of Chemical Engineering , University of Patras , Patras 26504 , Greece
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15
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Romero-Muñiz C, Martín-Recio A, Pou P, Gómez-Rodríguez JM, Pérez R. Substrate-induced enhancement of the chemical reactivity in metal-supported graphene. Phys Chem Chem Phys 2018; 20:19492-19499. [PMID: 29998270 DOI: 10.1039/c8cp02827c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Graphene is commonly regarded as an inert material. However, it is well known that the presence of defects or substitutional hetero-atoms confers graphene promising catalytic properties. In this work, we use first-principles calculations to show that it is also possible to enhance the chemical reactivity of a graphene layer by simply growing it on an appropriate substrate. Our comprehensive study demonstrates that, in strongly interacting substrates like Rh(111), graphene adopts highly rippled structures that exhibit areas with distinctive chemical behaviors. According to the local coupling with the substrate, we find areas with markedly different adsorption, dissociation and diffusion pathways for both molecular and atomic oxygen, including a significant change in the nature of the adsorbed molecular and dissociated states, and a dramatic reduction (∼60%) of the O2 dissociation energy barrier with respect to free-standing graphene. Our results show that the graphene-metal interaction represents an additional and powerful handle to tailor the graphene chemical properties with potential applications to nano patterning, graphene functionalization and sensing devices.
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Affiliation(s)
- Carlos Romero-Muñiz
- Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain.
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16
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Li BW, Luo D, Zhu L, Zhang X, Jin S, Huang M, Ding F, Ruoff RS. Orientation-Dependent Strain Relaxation and Chemical Functionalization of Graphene on a Cu(111) Foil. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:1706504. [PMID: 29337385 DOI: 10.1002/adma.201706504] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 12/05/2017] [Indexed: 06/07/2023]
Abstract
Epitaxial graphene grown on single crystal Cu(111) foils by chemical vapor deposition is found to be free of wrinkles and under biaxial compressive strain. The compressive strain in the epitaxial regions (0.25-0.40%) is higher than regions where the graphene is not epitaxial with the underlying surface (0.20-0.25%). This orientation-dependent strain relaxation is through the loss of local adhesion and the generation of graphene wrinkles. Density functional theory calculations suggest a large frictional force between the epitaxial graphene and the Cu(111) substrate, and this is therefore an energy barrier to the formation of wrinkles in the graphene. Enhanced chemical reactivity is found in epitaxial graphene on Cu(111) foils as compared to graphene on polycrystalline Cu foils for certain chemical reactions. A higher compressive strain possibly favors lowering the formation energy and/or the energy gap between the initial and transition states, either of which can lead to an increase in chemical reactivity.
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Affiliation(s)
- Bao-Wen Li
- Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Da Luo
- Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Liyan Zhu
- Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Xu Zhang
- Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Sunghwan Jin
- Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Ming Huang
- Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Feng Ding
- Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Rodney S Ruoff
- Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
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17
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Weng S, Ning H, Fu T, Hu N, Zhao Y, Huang C, Peng X. Molecular dynamics study of strengthening mechanism of nanolaminated graphene/Cu composites under compression. Sci Rep 2018; 8:3089. [PMID: 29449626 PMCID: PMC5814566 DOI: 10.1038/s41598-018-21390-1] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 02/01/2018] [Indexed: 11/10/2022] Open
Abstract
Molecular dynamics simulations of nanolaminated graphene/Cu (NGCu) and pure Cu under compression are conducted to investigate the underlying strengthening mechanism of graphene and the effect of lamella thickness. It is found that the stress-strain curves of NGCu undergo 3 regimes i.e. the elastic regime I, plastic strengthening regime II and plastic flow regime III. Incorporating graphene monolayer is proved to simultaneously contribute to the strength and ductility of the composites and the lamella thickness has a great effect on the mechanical properties of NGCu composites. Different strengthening mechanisms play main role in different regimes, the transition of mechanisms is found to be related to the deformation behavior. Graphene affected zone is developed and integrated with rule of mixtures and confined layer slip model to describe the elastic properties of NGCu and the strengthening effect of the incorporated graphene.
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Affiliation(s)
- Shayuan Weng
- College of Aerospace Engineering, Chongqing University, Chongqing, 400044, P. R. China
| | - Huiming Ning
- College of Aerospace Engineering, Chongqing University, Chongqing, 400044, P. R. China.
| | - Tao Fu
- College of Aerospace Engineering, Chongqing University, Chongqing, 400044, P. R. China
| | - Ning Hu
- College of Aerospace Engineering, Chongqing University, Chongqing, 400044, P. R. China. .,Key Laboratory of Optoelectronic Technology & Systems, Education Ministry of China, Chongqing University, Chongqing, 400044, P.R. China.
| | - Yinbo Zhao
- College of Aerospace Engineering, Chongqing University, Chongqing, 400044, P. R. China
| | - Cheng Huang
- College of Aerospace Engineering, Chongqing University, Chongqing, 400044, P. R. China
| | - Xianghe Peng
- College of Aerospace Engineering, Chongqing University, Chongqing, 400044, P. R. China
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18
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Rojas WY, Winter AD, Grote J, Kim SS, Naik RR, Williams AD, Weiland C, Principe E, Fischer DA, Banerjee S, Prendergast D, Campo EM. Strain and Bond Length Dynamics upon Growth and Transfer of Graphene by NEXAFS Spectroscopy from First-Principles and Experiment. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:1783-1794. [PMID: 29286662 DOI: 10.1021/acs.langmuir.7b03260] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
As the quest toward novel materials proceeds, improved characterization technologies are needed. In particular, the atomic thickness in graphene and other 2D materials renders some conventional technologies obsolete. Characterization technologies at wafer level are needed with enough sensitivity to detect strain in order to inform fabrication. In this work, NEXAFS spectroscopy was combined with simulations to predict lattice parameters of graphene grown on copper and further transferred to a variety of substrates. The strains associated with the predicted lattice parameters are in agreement with experimental findings. The approach presented here holds promise to effectively measure strain in graphene and other 2D systems at wafer levels to inform manufacturing environments.
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Affiliation(s)
- W Y Rojas
- School of Electronic Engineering, Bangor University , Bangor LL57 1UT, United Kingdom
| | - A D Winter
- School of Electronic Engineering, Bangor University , Bangor LL57 1UT, United Kingdom
| | - J Grote
- Materials and Manufacturing Directorate, Air Force Research Laboratory , Wright-Patterson AFB, Ohio 45433, United States
| | - S S Kim
- Materials and Manufacturing Directorate, Air Force Research Laboratory , Wright-Patterson AFB, Ohio 45433, United States
| | - R R Naik
- Materials and Manufacturing Directorate, Air Force Research Laboratory , Wright-Patterson AFB, Ohio 45433, United States
| | - A D Williams
- Materials and Manufacturing Directorate, Air Force Research Laboratory , Wright-Patterson AFB, Ohio 45433, United States
| | - C Weiland
- Synchrotron Research, Inc. , Melbourne, Florida 32901, United States
| | - E Principe
- Synchrotron Research, Inc. , Melbourne, Florida 32901, United States
| | - D A Fischer
- National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States
| | - S Banerjee
- Departments of Chemistry and Materials Science and Engineering, Texas A&M University , College Station, Texas 77842-3012, United States
| | - D Prendergast
- The Molecular Foundry, Materials Science Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - E M Campo
- School of Electronic Engineering, Bangor University , Bangor LL57 1UT, United Kingdom
- Department of Physics and Astronomy, University of Texas at San Antonio , San Antonio, Texas 78249, United States
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19
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Ji HG, Maruyama M, Aji AS, Okada S, Matsuda K, Ago H. van der Waals interaction-induced photoluminescence weakening and multilayer growth in epitaxially aligned WS2. Phys Chem Chem Phys 2018; 20:29790-29797. [DOI: 10.1039/c8cp04418j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Influence of sapphire substrate on the epitaxial growth of WS2 was investigated in terms of the optical and electrical properties.
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Affiliation(s)
- Hyun Goo Ji
- Interdisciplinary Graduate School of Engineering Sciences
- Kyushu University
- Fukuoka 816-8580
- Japan
| | - Mina Maruyama
- Graduate School of Pure and Applied Sciences
- University of Tsukuba
- Ibaraki 305-8571
- Japan
| | - Adha Sukma Aji
- Interdisciplinary Graduate School of Engineering Sciences
- Kyushu University
- Fukuoka 816-8580
- Japan
| | - Susumu Okada
- Graduate School of Pure and Applied Sciences
- University of Tsukuba
- Ibaraki 305-8571
- Japan
| | - Kazunari Matsuda
- Institute of Advanced Energy
- Kyoto University
- Uji
- Kyoto, 611-0011
- Japan
| | - Hiroki Ago
- Interdisciplinary Graduate School of Engineering Sciences
- Kyushu University
- Fukuoka 816-8580
- Japan
- Global Innovation Center (GIC)
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20
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Chae S, Jin Choi W, Sang Chae S, Jang S, Chang H, Lee TI, Kim YS, Lee JO. Graphene as a thin-film catalyst booster: graphene-catalyst interface plays a critical role. NANOTECHNOLOGY 2017; 28:495708. [PMID: 29048327 DOI: 10.1088/1361-6528/aa94b0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Due to its extreme thinness, graphene can transmit some surface properties of its underlying substrate, a phenomenon referred to as graphene transparency. Here we demonstrate the application of the transparency of graphene as a protector of thin-film catalysts and a booster of their catalytic efficiency. The photocatalytic degradation of dye molecules by ZnO thin films was chosen as a model system. A ZnO thin film coated with monolayer graphene showed greater catalytic efficiency and long-term stability than did bare ZnO. Interestingly, we found the catalytic efficiency of the graphene-coated ZnO thin film to depend critically on the nature of the bottom ZnO layer; graphene transferred to a relatively rough, sputter-coated ZnO thin film showed rather poor catalytic degradation of the dye molecules while a smooth sol-gel-synthesized ZnO covered with monolayer graphene showed enhanced catalytic degradation. Based on a systematic investigation of the interface between graphene and ZnO thin films, we concluded the transparency of graphene to be critically dependent on its interface with a supporting substrate. Graphene supported on an atomically flat substrate was found to efficiently transmit the properties of the substrate, but graphene suspended on a substrate with a rough nanoscale topography was completely opaque to the substrate properties. Our experimental observations revealed the morphology of the substrate to be a key factor affecting the transparency of graphene, and should be taken into account in order to optimally apply graphene as a protector of catalytic thin films and a booster of their catalysis.
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Affiliation(s)
- Sieun Chae
- Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Republic of Korea. Program in Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 08826, Republic of Korea
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21
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Environment-insensitive and gate-controllable photocurrent enabled by bandgap engineering of MoS 2 junctions. Sci Rep 2017; 7:44768. [PMID: 28322299 PMCID: PMC5359557 DOI: 10.1038/srep44768] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 02/14/2017] [Indexed: 11/08/2022] Open
Abstract
Two-dimensional (2D) materials are composed of atomically thin crystals with an enormous surface-to-volume ratio, and their physical properties can be easily subjected to the change of the chemical environment. Encapsulation with other layered materials, such as hexagonal boron nitride, is a common practice; however, this approach often requires inextricable fabrication processes. Alternatively, it is intriguing to explore methods to control transport properties in the circumstance of no encapsulated layer. This is very challenging because of the ubiquitous presence of adsorbents, which can lead to charged-impurity scattering sites, charge traps, and recombination centers. Here, we show that the short-circuit photocurrent originated from the built-in electric field at the MoS2 junction is surprisingly insensitive to the gaseous environment over the range from a vacuum of 1 × 10−6 Torr to ambient condition. The environmental insensitivity of the short-circuit photocurrent is attributed to the characteristic of the diffusion current that is associated with the gradient of carrier density. Conversely, the photocurrent with bias exhibits typical persistent photoconductivity and greatly depends on the gaseous environment. The observation of environment-insensitive short-circuit photocurrent demonstrates an alternative method to design device structure for 2D-material-based optoelectronic applications.
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22
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Na SR, Wang X, Piner RD, Huang R, Willson CG, Liechti KM. Cracking of Polycrystalline Graphene on Copper under Tension. ACS NANO 2016; 10:9616-9625. [PMID: 27652909 DOI: 10.1021/acsnano.6b05101] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Roll-to-roll manufacturing of graphene is attractive because of its compatibility with flexible substrates and its promise of high-speed production. Several prototype roll-to-roll systems have been demonstrated, which produce large-scale graphene on polymer films for transparent conducting film applications.1-4 In spite of such progress, the quality of graphene may be influenced by the tensile forces that are applied during roll-to-roll transfer. To address this issue, we conducted in situ tensile experiments on copper foil coated with graphene grown by chemical vapor deposition, which were carried out in a scanning electron microscope. Channel cracks, which were perpendicular to the loading direction, initiated over the entire graphene monolayer at applied tensile strain levels that were about twice the yield strain of the (annealed) copper. The spacing between the channel cracks decreased with increasing applied strain, and new graphene wrinkles that were parallel to the loading direction appeared. These morphological features were confirmed in more detail by atomic force microscopy. Raman spectroscopy was used to determine the strain in the graphene, which was related to the degradation of the graphene/copper interface. The experimental data allowed the fracture toughness of graphene and interfacial properties of the graphene/copper interface to be extracted based on classical channel crack and shear-lag models. This study not only deepens our understanding of the mechanical and interfacial behavior of graphene on copper but also provides guidelines for the design of roll-to-roll processes for the dry transfer of graphene.
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Affiliation(s)
- Seung Ryul Na
- Department of Aerospace Engineering and Engineering Mechanics, Research Center for the Mechanics of Solids, Structures and Materials, and ‡The Materials Science and Engineering Program, The University of Texas at Austin , Austin, Texas 78712, United States
| | - Xiaohan Wang
- Department of Aerospace Engineering and Engineering Mechanics, Research Center for the Mechanics of Solids, Structures and Materials, and ‡The Materials Science and Engineering Program, The University of Texas at Austin , Austin, Texas 78712, United States
| | - Richard D Piner
- Department of Aerospace Engineering and Engineering Mechanics, Research Center for the Mechanics of Solids, Structures and Materials, and ‡The Materials Science and Engineering Program, The University of Texas at Austin , Austin, Texas 78712, United States
| | - Rui Huang
- Department of Aerospace Engineering and Engineering Mechanics, Research Center for the Mechanics of Solids, Structures and Materials, and ‡The Materials Science and Engineering Program, The University of Texas at Austin , Austin, Texas 78712, United States
| | - C Grant Willson
- Department of Aerospace Engineering and Engineering Mechanics, Research Center for the Mechanics of Solids, Structures and Materials, and ‡The Materials Science and Engineering Program, The University of Texas at Austin , Austin, Texas 78712, United States
| | - Kenneth M Liechti
- Department of Aerospace Engineering and Engineering Mechanics, Research Center for the Mechanics of Solids, Structures and Materials, and ‡The Materials Science and Engineering Program, The University of Texas at Austin , Austin, Texas 78712, United States
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23
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24
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Anagnostopoulos G, Pappas PN, Li Z, Kinloch IA, Young R, Novoselov KS, Lu CY, Pugno N, Parthenios J, Galiotis C, Papagelis K. Mechanical Stability of Flexible Graphene-Based Displays. ACS APPLIED MATERIALS & INTERFACES 2016; 8:22605-22614. [PMID: 27494211 PMCID: PMC5022774 DOI: 10.1021/acsami.6b05227] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 08/05/2016] [Indexed: 05/29/2023]
Abstract
The mechanical behavior of a prototype touch panel display, which consists of two layers of CVD graphene embedded into PET films, is investigated in tension and under contact-stress dynamic loading. In both cases, laser Raman spectroscopy was employed to assess the stress transfer efficiency of the embedded graphene layers. The tensile behavior was found to be governed by the "island-like" microstructure of the CVD graphene, and the stress transfer efficiency was dependent on the size of graphene "islands" but also on the yielding behavior of PET at relatively high strains. Finally, the fatigue tests, which simulate real operation conditions, showed that the maximum temperature gradient developed at the point of "finger" contact after 80 000 cycles does not exceed the glass transition temperature of the PET matrix. The effect of these results on future product development and the design of new graphene-based displays are discussed.
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Affiliation(s)
- George Anagnostopoulos
- Institute of Chemical
Engineering Sciences, Foundation for Research
and Technology − Hellas (FORTH/ICE-HT), Patras 265 04, Greece
| | - Panagiotis-Nektarios Pappas
- Institute of Chemical
Engineering Sciences, Foundation for Research
and Technology − Hellas (FORTH/ICE-HT), Patras 265 04, Greece
| | - Zheling Li
- School of Materials, School of Physics and Astronomy, and BGT Materials Limited, 2.312 Photon
Science Institute, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Ian A. Kinloch
- School of Materials, School of Physics and Astronomy, and BGT Materials Limited, 2.312 Photon
Science Institute, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Robert
J. Young
- School of Materials, School of Physics and Astronomy, and BGT Materials Limited, 2.312 Photon
Science Institute, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Kostya S. Novoselov
- School of Materials, School of Physics and Astronomy, and BGT Materials Limited, 2.312 Photon
Science Institute, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Ching Yu Lu
- School of Materials, School of Physics and Astronomy, and BGT Materials Limited, 2.312 Photon
Science Institute, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Nicola Pugno
- Laboratory of Bio-Inspired and Graphene
Nanomechanics, Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, I-38123 Trento, Italy
- Center for Materials and
Microsystems, Fondazione Bruno Kessler, I-38123 Trento, Italy
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - John Parthenios
- Institute of Chemical
Engineering Sciences, Foundation for Research
and Technology − Hellas (FORTH/ICE-HT), Patras 265 04, Greece
| | - Costas Galiotis
- Institute of Chemical
Engineering Sciences, Foundation for Research
and Technology − Hellas (FORTH/ICE-HT), Patras 265 04, Greece
- Department of Chemical Engineering,
and Department of Materials
Science, University of Patras, Patras 26504, Greece
| | - Konstantinos Papagelis
- Institute of Chemical
Engineering Sciences, Foundation for Research
and Technology − Hellas (FORTH/ICE-HT), Patras 265 04, Greece
- Department of Chemical Engineering,
and Department of Materials
Science, University of Patras, Patras 26504, Greece
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25
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Zaretski AV, Root SE, Savchenko A, Molokanova E, Printz AD, Jibril L, Arya G, Mercola M, Lipomi DJ. Metallic Nanoislands on Graphene as Highly Sensitive Transducers of Mechanical, Biological, and Optical Signals. NANO LETTERS 2016; 16:1375-80. [PMID: 26765039 PMCID: PMC4751512 DOI: 10.1021/acs.nanolett.5b04821] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 01/08/2016] [Indexed: 05/28/2023]
Abstract
This article describes an effect based on the wetting transparency of graphene; the morphology of a metallic film (≤20 nm) when deposited on graphene by evaporation depends strongly on the identity of the substrate supporting the graphene. This control permits the formation of a range of geometries, such as tightly packed nanospheres, nanocrystals, and island-like formations with controllable gaps down to 3 nm. These graphene-supported structures can be transferred to any surface and function as ultrasensitive mechanical signal transducers with high sensitivity and range (at least 4 orders of magnitude of strain) for applications in structural health monitoring, electronic skin, measurement of the contractions of cardiomyocytes, and substrates for surface-enhanced Raman scattering (SERS, including on the tips of optical fibers). These composite films can thus be treated as a platform technology for multimodal sensing. Moreover, they are low profile, mechanically robust, semitransparent and have the potential for reproducible manufacturing over large areas.
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Affiliation(s)
- Aliaksandr V. Zaretski
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0448, United States
| | - Samuel E. Root
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0448, United States
| | - Alex Savchenko
- Department of Bioengineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0412, United States
- Sanford Burnham Prebys Medical Discovery
Institute, 10901 North
Torrey Pines Road., La Jolla, California 92037, United States
| | | | - Adam D. Printz
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0448, United States
| | - Liban Jibril
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0448, United States
| | - Gaurav Arya
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0448, United States
| | - Mark Mercola
- Department of Bioengineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0412, United States
- Sanford Burnham Prebys Medical Discovery
Institute, 10901 North
Torrey Pines Road., La Jolla, California 92037, United States
| | - Darren J. Lipomi
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0448, United States
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26
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Bronsgeest MS, Bendiab N, Mathur S, Kimouche A, Johnson HT, Coraux J, Pochet P. Strain Relaxation in CVD Graphene: Wrinkling with Shear Lag. NANO LETTERS 2015; 15:5098-5104. [PMID: 26171667 DOI: 10.1021/acs.nanolett.5b01246] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We measure uniaxial strain fields in the vicinity of edges and wrinkles in graphene prepared by chemical vapor deposition (CVD), by combining microscopy techniques and local vibrational characterization. These strain fields have magnitudes of several tenths of a percent and extend across micrometer distances. The nonlinear shear-lag model remarkably captures these strain fields in terms of the graphene-substrate interaction and provides a complete understanding of strain-relieving wrinkles in graphene for any level of graphene-substrate coherency.
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Affiliation(s)
- Merijntje S Bronsgeest
- †Université Grenoble Alpes, F-38000, Grenoble, France
- ‡CEA, INAC-SP2M, F-38054, Grenoble, France
| | - Nedjma Bendiab
- †Université Grenoble Alpes, F-38000, Grenoble, France
- §CNRS, Inst NEEL, F-38042, Grenoble, France
| | - Shashank Mathur
- †Université Grenoble Alpes, F-38000, Grenoble, France
- ‡CEA, INAC-SP2M, F-38054, Grenoble, France
- §CNRS, Inst NEEL, F-38042, Grenoble, France
| | - Amina Kimouche
- †Université Grenoble Alpes, F-38000, Grenoble, France
- §CNRS, Inst NEEL, F-38042, Grenoble, France
| | - Harley T Johnson
- †Université Grenoble Alpes, F-38000, Grenoble, France
- ∥Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801, United States
| | - Johann Coraux
- †Université Grenoble Alpes, F-38000, Grenoble, France
- §CNRS, Inst NEEL, F-38042, Grenoble, France
| | - Pascal Pochet
- †Université Grenoble Alpes, F-38000, Grenoble, France
- ‡CEA, INAC-SP2M, F-38054, Grenoble, France
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27
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Tang X, Xie Z, Huang Q, Chen G, Hou M, Yi B. Mass-transport-controlled, large-area, uniform deposition of carbon nanofibers and their application in gas diffusion layers of fuel cells. NANOSCALE 2015; 7:7971-7979. [PMID: 25865711 DOI: 10.1039/c5nr00022j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The effect of mass transport on the growth characteristics of large-area vapor-grown carbon nanofibers (CNFs) was investigated by adjusting the substrate deposition angle (α). The catalyst precursor solution was coated onto one side of a 2D porous carbon paper substrate via a decal printing method. The results showed that the CNFs were grown on only one side of the substrate and α was found to significantly affect the growth uniformity. At α = 0°, the growth thickness, the density, the microstructure and the yield of the CNF film were uniform across the substrate surface, whereas the growth uniformity decreased with increasing α, suggesting that the large-area CNF deposition processes were mass-transport-controlled. Computational fluid dynamics simulations of the gas diffusion processes revealed the homogeneous distributions of the carbon-source-gas concentration, pressure, and velocity near the substrate surface at α = 0°, which were the important factors in achieving the mass-transport-limited uniform CNF growth. The homogeneity of the field distributions decreased with increasing α, in accordance with the variation in the growth uniformity with α. When used as a micro-porous layer, the uniform CNF film enabled higher proton exchange membrane fuel cell performance in comparison with commercial carbon black by virtue of its improved electronic and mass-transport properties confirmed by the electrochemical impedance spectroscopy results.
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Affiliation(s)
- Xian Tang
- State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China.
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28
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Na SR, Suk JW, Tao L, Akinwande D, Ruoff RS, Huang R, Liechti KM. Selective mechanical transfer of graphene from seed copper foil using rate effects. ACS NANO 2015; 9:1325-35. [PMID: 25646863 DOI: 10.1021/nn505178g] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
A very fast, dry transfer process based on mechanical delamination successfully effected the transfer of large-area, CVD grown graphene on copper foil to silicon. This has been achieved by bonding silicon backing layers to both sides of the graphene-coated copper foil with epoxy and applying a suitably high separation rate to the backing layers. At the highest separation rate considered (254.0 μm/s), monolayer graphene was completely transferred from the copper foil to the target silicon substrate. On the other hand, the lowest rate (25.4 μm/s) caused the epoxy to be completely separated from the graphene. Fracture mechanics analyses were used to determine the adhesion energy between graphene and its seed copper foil (6.0 J/m(2)) and between graphene and the epoxy (3.4 J/m(2)) at the respective loading rates. Control experiments for the epoxy/silicon interface established a rate dependent adhesion, which supports the hypothesis that the adhesion of the graphene/epoxy interface was higher than that of the graphene/copper interface at the higher separation rate, thereby providing a controllable mechanism for selective transfer of graphene in future nanofabrication systems such as roll-to-roll transfer.
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Affiliation(s)
- Seung Ryul Na
- Department of Aerospace Engineering and Engineering Mechanics, Research Center for the Mechanics of Solids, Structures and Materials, ‡Department of Mechanical Engineering and The Materials Science and Engineering Program, and §Department of Electrical and Computer Engineering, The University of Texas at Austin Austin, Texas 78712, United States
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29
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Chung TF, He R, Wu TL, Chen YP. Optical phonons in twisted bilayer graphene with gate-induced asymmetric doping. NANO LETTERS 2015; 15:1203-1210. [PMID: 25621859 DOI: 10.1021/nl504318a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Twisted bilayer graphene (tBLG) devices with ion gel gate dielectrics are studied using Raman spectroscopy in the twist angle regime where a resonantly enhanced G band can be observed. We observe prominent splitting and intensity quenching on the G Raman band when the carrier density is tuned away from charge neutrality. This G peak splitting is attributed to asymmetric charge doping in the two graphene layers, which reveals individual phonon self-energy renormalization of the two weakly coupled layers of graphene. We estimate the effective interlayer capacitance at low doping density of tBLG using an interlayer screening model. The anomalous intensity quenching of both G peaks is ascribed to the suppression of resonant interband transitions between the two saddle points (van Hove singularities) that are displaced in the momentum space by gate-tuning. In addition, we observe a softening (hardening) of the R Raman band, a superlattice-induced phonon mode in tBLG, in electron (hole) doping. Our results demonstrate that gate modulation can be used to control the optoelectronic and vibrational properties in tBLG devices.
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Affiliation(s)
- Ting-Fung Chung
- Department of Physics and Astronomy and ‡Birck Nanotechnology Center, Purdue University , West Lafayette, Indiana 47907, United States
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30
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Zhao L, He R, Zabet-Khosousi A, Kim KS, Schiros T, Roth M, Kim P, Flynn GW, Pinczuk A, Pasupathy AN. Dopant segregation in polycrystalline monolayer graphene. NANO LETTERS 2015; 15:1428-1436. [PMID: 25625227 DOI: 10.1021/nl504875x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Heterogeneity in dopant concentration has long been important to the electronic properties in chemically doped materials. In this work, we experimentally demonstrate that during the chemical vapor deposition process, in contrast to three-dimensional polycrystals, the substitutional nitrogen atoms avoid crystal grain boundaries and edges over micron length scales while distributing uniformly in the interior of each grain. This phenomenon is universally observed independent of the details of the growth procedure such as temperature, pressure, substrate, and growth precursor.
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Affiliation(s)
- Liuyan Zhao
- Department of Physics, Columbia University , New York, New York 10027, United States
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31
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Qi Y, Zhou X, Liu M, Li Q, Ma D, Zhang Y, Liu Z. Controllable synthesis of graphene using novel aromatic 1,3,5-triethynylbenzene molecules on Rh(111). RSC Adv 2015. [DOI: 10.1039/c5ra12848j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
1,3,5-Triethynylbenzene is selected as carbon precursor for graphene synthesis on Rh(111). The temperature-programmed annealing and direct annealing growth pathways are designed to synthesize high-quality graphene.
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Affiliation(s)
- Yue Qi
- Center for Nanochemistry
- Beijing Science and Engineering Center for Nanocarbons
- Beijing National Laboratory for Molecular Sciences
- College of Chemistry and Molecular Engineering
- Academy for Advanced Interdisciplinary Studies
| | - Xiebo Zhou
- Department of Materials Science and Engineering
- College of Engineering
- Peking University
- Beijing 100871
- China
| | - Mengxi Liu
- Center for Nanochemistry
- Beijing Science and Engineering Center for Nanocarbons
- Beijing National Laboratory for Molecular Sciences
- College of Chemistry and Molecular Engineering
- Academy for Advanced Interdisciplinary Studies
| | - Qiucheng Li
- Center for Nanochemistry
- Beijing Science and Engineering Center for Nanocarbons
- Beijing National Laboratory for Molecular Sciences
- College of Chemistry and Molecular Engineering
- Academy for Advanced Interdisciplinary Studies
| | - Donglin Ma
- Center for Nanochemistry
- Beijing Science and Engineering Center for Nanocarbons
- Beijing National Laboratory for Molecular Sciences
- College of Chemistry and Molecular Engineering
- Academy for Advanced Interdisciplinary Studies
| | - Yanfeng Zhang
- Center for Nanochemistry
- Beijing Science and Engineering Center for Nanocarbons
- Beijing National Laboratory for Molecular Sciences
- College of Chemistry and Molecular Engineering
- Academy for Advanced Interdisciplinary Studies
| | - Zhongfan Liu
- Center for Nanochemistry
- Beijing Science and Engineering Center for Nanocarbons
- Beijing National Laboratory for Molecular Sciences
- College of Chemistry and Molecular Engineering
- Academy for Advanced Interdisciplinary Studies
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32
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Sun XY, Wu R, Xia R, Xu YJ. Blister formation in graphene coating on the nanoparticle decorated copper surface. RSC Adv 2014. [DOI: 10.1039/c4ra08050e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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33
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Giant spin Hall effect in graphene grown by chemical vapour deposition. Nat Commun 2014; 5:4748. [PMID: 25175340 DOI: 10.1038/ncomms5748] [Citation(s) in RCA: 155] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 07/18/2014] [Indexed: 12/21/2022] Open
Abstract
Advances in large-area graphene synthesis via chemical vapour deposition on metals like copper were instrumental in the demonstration of graphene-based novel, wafer-scale electronic circuits and proof-of-concept applications such as flexible touch panels. Here, we show that graphene grown by chemical vapour deposition on copper is equally promising for spintronics applications. In contrast to natural graphene, our experiments demonstrate that chemically synthesized graphene has a strong spin-orbit coupling as high as 20 meV giving rise to a giant spin Hall effect. The exceptionally large spin Hall angle ~0.2 provides an important step towards graphene-based spintronics devices within existing complementary metal-oxide-semiconductor technology. Our microscopic model shows that unavoidable residual copper adatom clusters act as local spin-orbit scatterers and, in the resonant scattering limit, induce transverse spin currents with enhanced skew-scattering contribution. Our findings are confirmed independently by introducing metallic adatoms-copper, silver and gold on exfoliated graphene samples.
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34
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Eres G, Regmi M, Rouleau CM, Chen J, Ivanov IN, Puretzky AA, Geohegan DB. Cooperative island growth of large-area single-crystal graphene on copper using chemical vapor deposition. ACS NANO 2014; 8:5657-69. [PMID: 24833238 DOI: 10.1021/nn500209d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In this work we explore the kinetics of single-crystal graphene growth as a function of nucleation density. In addition to the standard methods for suppressing nucleation of graphene by pretreatment of Cu foils using oxidation, annealing, and reduction of the Cu foils prior to growth, we introduce a new method that further reduces the graphene nucleation density by interacting directly with the growth process at the onset of nucleation. The successive application of these two methods results in roughly 3 orders of magnitude reduction in graphene nucleation density. We use a kinetic model to show that at vanishingly low nucleation densities carbon incorporation occurs by a cooperative island growth mechanism that favors the formation of substrate-size single-crystal graphene. The model reveals that the cooperative growth of millimeter-size single-crystal graphene grains occurs by roughly 3 orders of magnitude increase in the reactive sticking probability of methane compared to that in random island nucleation.
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Affiliation(s)
- Gyula Eres
- Materials Science and Technology Division, and ‡Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States
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35
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He Y, Chen WF, Yu WB, Ouyang G, Yang GW. Anomalous interface adhesion of graphene membranes. Sci Rep 2014; 3:2660. [PMID: 24036502 PMCID: PMC3773622 DOI: 10.1038/srep02660] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 08/21/2013] [Indexed: 11/17/2022] Open
Abstract
In order to understand the anomalous interface adhesion properties between graphene membranes and their substrates, we have developed a theoretical method to calibrate the interface adhesion energy of monolayer and multilayer graphene on substrates based on the bond relaxation consideration. Four kinds of interfaces, including graphene/SiO2, graphene/Cu, graphene/Cu/Ni and Cu/graphene/Ni, were taken into account. It was found that the membrane thickness and the interface confinement condition determine the adhesion energy. The relationship between the critical interface separation and the graphene thickness showed that the interface separation in the self-equilibrium state drops with decreasing membrane thickness. The size-dependent Young's modulus of graphene membrane and the interfacial condition were responsible for the novel interface adhesion energy. The proposed theory was expected to be applied to the design of graphene-based devices.
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Affiliation(s)
- Y He
- Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of the Ministry of Education, Department of Physics, Hunan Normal University, Changsha 410081, Hunan, China
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36
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Liu L, Niu Z, Zhang L, Chen X. Structural diversity of bulky graphene materials. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2014; 10:2200-2214. [PMID: 24668900 DOI: 10.1002/smll.201400144] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 02/12/2014] [Indexed: 06/03/2023]
Abstract
The unique two-dimensional (2D) structure and chemical properties of graphene and its derivatives make it a distinctive nanoscale building block for constructing novel bulky architectures with different dimensions, such as 1D fibers, 2D films and 3D architectures. These bulky graphene materials, depending on the manner in which graphene sheets are assembled, show a variety of fascinating features that cannot be achieved from individual graphene sheet or conventional materials. Thus, over the past several years, considerable effort has been expended in fabricating various structures of bulky graphene materials and developing their corresponding applications. Here, we present a broad and comprehensive overview of the recent developments in expanding the structural diversity of bulky graphene materials and their applications in energy storage and conversion, composites, environmental remediation, etc. Finally, prospects and further developments in this exciting field of bulky graphene materials are also suggested.
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Affiliation(s)
- Lili Liu
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798
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37
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38
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Eco-friendly graphene synthesis on Cu foil electroplated by reusing Cu etchants. Sci Rep 2014; 4:4830. [PMID: 24777344 PMCID: PMC5381280 DOI: 10.1038/srep04830] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 04/09/2014] [Indexed: 11/21/2022] Open
Abstract
Graphene film grown by chemical vapor deposition using Cu substrate is promising for industrial applications. After etching the Cu substrate, which is essential step in graphene transfer process, the etchant solution must be chemically treated to prevent water pollution. Here we investigated that a method of reusing Cu etchant used to synthesize graphene, the synthesis of graphene on the resulting reused Cu films (R-G), and the application of R-G to organic light-emitting diodes (OLEDs) and organic photovoltaic cells (OPVs). The turn-on voltage of OLEDs based on the R-G electrode was 4.2 V, and the efficiencies of OPVs based on the R-G electrode were 5.9–5.95%, that are similar to or better than those of the indium-tin-oxide-based devices. These results suggest that the reusing of Cu foil by the electroplating method could reduce the cost of graphene synthesis, thus opening a wide range of applications in graphene electronics.
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39
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Hu B, Wei Z, Ago H, Jin Y, Xia M, Luo Z, Pan Q, Liu Y. Effects of substrate and transfer on CVD-grown graphene over sapphire-induced Cu films. Sci China Chem 2014. [DOI: 10.1007/s11426-014-5073-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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40
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Ni GX, Yang HZ, Ji W, Baeck SJ, Toh CT, Ahn JH, Pereira VM, Ozyilmaz B. Tuning optical conductivity of large-scale CVD graphene by strain engineering. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:1081-6. [PMID: 24327432 DOI: 10.1002/adma.201304156] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2013] [Revised: 09/10/2013] [Indexed: 05/06/2023]
Abstract
A controllable optical anisotropy in CVD graphene is shown. The transparency in the visible range of pre-strained CVD graphene exhibits a periodic modulation as a function of polarization direction. The strain sensitivity of the optical response of graphene demonstrated here can be effectively utilized towards novel ultra-thin optical devices and strain sensing applications.
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Affiliation(s)
- Guang-Xin Ni
- Department of Physics, 2 Science Drive 3, National University of Singapore, Singapore, 117542; Graphene Research Centre, 6 Science Drive 2, National University of Singapore, Singapore, 117546; NanoCore, 4 Engineering Drive 3, National University of Singapore, Singapore, 117576
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41
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Zhao Y, Liu X, Lei DY, Chai Y. Effects of surface roughness of Ag thin films on surface-enhanced Raman spectroscopy of graphene: spatial nonlocality and physisorption strain. NANOSCALE 2014; 6:1311-7. [PMID: 24336904 DOI: 10.1039/c3nr05303b] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Metallic nanostructures are widely used for surface-enhanced Raman spectroscopy (SERS). Nanoscale surface corrugation significantly affects the localized plasmon response and the subsequent Raman intensity of the molecules in close proximity to the nanostructures. Experimentally, the surface roughness of metal films can be controlled by adjusting the deposition conditions, and the resulting localized near-field properties can be probed by measuring the Raman spectrum of the conformally coated monolayer graphene. The well-known Raman characteristics of graphene and its atomic-level 2D nature make it an ideal test-bed for SERS measurements on corrugated metal films. In this work, we experimentally and theoretically study the effects of surface roughness of Ag thin films on the SERS of graphene. We find that the nonlocality effect of the metal dielectric response has to be taken into account for more accurate prediction of the SERS enhancement at large surface roughness. Our results also reveal that the effect of physisorption strain should be included to understand the Raman peak shift and spectral broadening. These observations are fundamentally important for understanding the SERS from metallic nanostructures with sub-nanoscale corrugation.
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Affiliation(s)
- Yuda Zhao
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, People's Republic of China.
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42
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Süle P, Szendrő M. The classical molecular dynamics simulation of graphene on Ru(0001) using a fitted Tersoff interface potential. SURF INTERFACE ANAL 2013. [DOI: 10.1002/sia.5344] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- P. Süle
- Research Centre for Natural Sciences; Institute for Technical Physics and Materials Science; Budapest Hungary
| | - M. Szendrő
- Department of Materials Physics; The University of Eötvös Lóránd; Budapest Hungary
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43
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On the growth mode of two-lobed curvilinear graphene domains at atmospheric pressure. Sci Rep 2013; 3:2571. [PMID: 23999168 PMCID: PMC3759841 DOI: 10.1038/srep02571] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 07/24/2013] [Indexed: 11/08/2022] Open
Abstract
We demonstrate the chemical vapor deposition (CVD) growth of 2-lobed symmetrical curvilinear graphene domains specifically on Cu{100} surface orientations at atmospheric pressure. We utilize electron backscattered diffraction, scanning electron microscopy and Raman spectroscopy to determine an as-yet unexplored growth mode producing such a shape and demonstrate how its growth and morphology are dependent on the underlying Cu crystal structure especially in the high CH4:H2 regime. We show that both monolayer and bilayer curvilinear domains are grown on Cu{100} surfaces; furthermore, we show that characteristic atmospheric pressure CVD hexagonal domains are grown on all other Cu facets with an isotropic growth rate which is more rapid than that on Cu{100}. These findings indicate that the Cu-graphene complex is predominant mechanistically at atmospheric pressure, which is an important step towards tailoring graphene properties via substrate engineering.
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44
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He R, Chung TF, Delaney C, Keiser C, Jauregui LA, Shand PM, Chancey CC, Wang Y, Bao J, Chen YP. Observation of low energy Raman modes in twisted bilayer graphene. NANO LETTERS 2013; 13:3594-601. [PMID: 23859121 DOI: 10.1021/nl4013387] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Two new Raman modes below 100 cm(-1) are observed in twisted bilayer graphene grown by chemical vapor deposition. The two modes are observed in a small range of twisting angle at which the intensity of the G Raman peak is strongly enhanced, indicating that these low energy modes and the G Raman mode share the same resonance enhancement mechanism, as a function of twisting angle. The ~94 cm(-1) mode (measured with a 532 nm laser excitation) is assigned to the fundamental layer breathing vibration (ZO' mode) mediated by the twisted bilayer graphene lattice, which lacks long-range translational symmetry. The dependence of this mode's frequency and line width on the rotational angle can be explained by the double resonance Raman process that is different from the previously identified Raman processes activated by twisted bilayer graphene superlattice. The dependence also reveals the strong impact of electronic-band overlaps of the two graphene layers. Another new mode at ~52 cm(-1), not observed previously in the bilayer graphene system, is tentatively attributed to a torsion mode in which the bottom and top graphene layers rotate out-of-phase in the plane.
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Affiliation(s)
- Rui He
- Department of Physics, University of Northern Iowa, Cedar Falls, Iowa 50614, United States.
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Ahn G, Kim HR, Ko TY, Choi K, Watanabe K, Taniguchi T, Hong BH, Ryu S. Optical probing of the electronic interaction between graphene and hexagonal boron nitride. ACS NANO 2013; 7:1533-1541. [PMID: 23301838 DOI: 10.1021/nn305306n] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Even weak van der Waals (vdW) adhesion between two-dimensional solids may perturb their various materials properties owing to their low dimensionality. Although the electronic structure of graphene has been predicted to be modified by the vdW interaction with other materials, its optical characterization has not been successful. In this report, we demonstrate that Raman spectroscopy can be utilized to detect a few percent decrease in the Fermi velocity (v(F)) of graphene caused by the vdW interaction with underlying hexagonal boron nitride (hBN). Our study also establishes Raman spectroscopic analysis which enables separation of the effects by the vdW interaction from those by mechanical strain or extra charge carriers. The analysis reveals that spectral features of graphene on hBN are mainly affected by change in v(F) and mechanical strain but not by charge doping, unlike graphene supported on SiO₂ substrates. Graphene on hBN was also found to be less susceptible to thermally induced hole doping.
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Affiliation(s)
- Gwanghyun Ahn
- Department of Applied Chemistry, Kyung Hee University, Yongin 446-701, Korea
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Hwang J, Kim M, Campbell D, Alsalman HA, Kwak JY, Shivaraman S, Woll AR, Singh AK, Hennig RG, Gorantla S, Rümmeli MH, Spencer MG. van der Waals epitaxial growth of graphene on sapphire by chemical vapor deposition without a metal catalyst. ACS NANO 2013; 7:385-395. [PMID: 23244231 DOI: 10.1021/nn305486x] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
van der Waals epitaxial growth of graphene on c-plane (0001) sapphire by CVD without a metal catalyst is presented. The effects of CH(4) partial pressure, growth temperature, and H(2)/CH(4) ratio were investigated and growth conditions optimized. The formation of monolayer graphene was shown by Raman spectroscopy, optical transmission, grazing incidence X-ray diffraction (GIXRD), and low voltage transmission electron microscopy (LVTEM). Electrical analysis revealed that a room temperature Hall mobility above 2000 cm(2)/V·s was achieved, and the mobility and carrier type were correlated to growth conditions. Both GIXRD and LVTEM studies confirm a dominant crystal orientation (principally graphene [10-10] || sapphire [11-20]) for about 80-90% of the material concomitant with epitaxial growth. The initial phase of the nucleation and the lateral growth from the nucleation seeds were observed using atomic force microscopy. The initial nuclei density was ~24 μm(-2), and a lateral growth rate of ~82 nm/min was determined. Density functional theory calculations reveal that the binding between graphene and sapphire is dominated by weak dispersion interactions and indicate that the epitaxial relation as observed by GIXRD is due to preferential binding of small molecules on sapphire during early stages of graphene formation.
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Affiliation(s)
- Jeonghyun Hwang
- School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA.
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Zhou H, Yu F, Tang D, Chen M, Yang H, Wang G, Guo Y, Sun L. Large physisorption strain and edge modification of Pd on monolayer graphene. NANOSCALE 2013; 5:124-127. [PMID: 23143014 DOI: 10.1039/c2nr32852f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Using Raman spectroscopic studies, we firstly report that Pd film deposition can induce a tensile strain at the interface between Pd and n-layer graphenes, which results in the splitting of the G peak and a red Raman shift of the 2D peak in monolayer graphene, and red Raman shifts of G and 2D peaks for other n-layer graphenes. In particular, this kind of tensile strain can be used as an effective way for edge modification or strain engineering in monolayer graphene.
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Affiliation(s)
- Haiqing Zhou
- National Centre for Nanoscience and Technology, Beijing 100190, China
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Bissett MA, Izumida W, Saito R, Ago H. Effect of domain boundaries on the Raman spectra of mechanically strained graphene. ACS NANO 2012; 6:10229-10238. [PMID: 23039066 DOI: 10.1021/nn304032f] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We investigate the effect of mechanical strain on graphene synthesized by chemical vapor deposition (CVD) transferred onto flexible polymer substrates by observing the change in the Raman spectrum and then compare this to the behavior of exfoliated graphene. Previous studies into the effect of strain on graphene have focused on mechanically exfoliated graphene, which consists of large single domains. However, for wide scale applications CVD produced films are more applicable, and these differ in morphology, instead consisting of a patchwork of smaller domains separated by domain boundaries. We find that under strain the Raman spectra of CVD graphene transferred onto a silicone elastomer exhibits unusual behavior, with the G and 2D band frequencies decreasing and increasing respectively with applied strain. This unusual Raman behavior is attributed to the presence of domain boundaries in polycrystalline graphene causing unexpected shifts in the electronic structure. This was confirmed by the lack of such behavior in mechanically exfoliated large domain graphene and also in large single-crystal graphene domains grown by CVD. Theoretical calculation of G band for a given large shear strain may explain the unexpected shifts while the shift of the Dirac points from the K point explain the conventional behavior of a 2D band under the strain.
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Affiliation(s)
- Mark A Bissett
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 816-8580, Japan
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Zhao S, Surwade SP, Li Z, Liu H. Photochemical oxidation of CVD-grown single layer graphene. NANOTECHNOLOGY 2012; 23:355703. [PMID: 22874100 DOI: 10.1088/0957-4484/23/35/355703] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
CVD-grown single layer graphene undergoes rapid photochemical oxidation in the presence of ultraviolet light and oxygen. The oxidation results in a homogeneous decay of the graphitic material; no nanoscale line cracks or pits were observed with an atomic force microscope. The conductivity of the graphene film decreases with an increasing degree of oxidation. It is crucial to understand and enhance the photochemical stability of graphene for its long term use as a transparent conducting material.
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Affiliation(s)
- Shichao Zhao
- College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou, People's Republic of China
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