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The Deformation of Wrinkled Graphene Zheling Li, Ian A. Kinloch, Robert J Young, Konstantin S. Novoselov, George Anagnostopoulos, John Parthenios, Costas Galiotis, Konstantinos Papagelis, Ching-Yu Lu, and Liam Britnell ACS Nano, Just Accepted Manuscript • Publication Date (Web): 12 Mar 2015 Downloaded from http://pubs.acs.org on March 13, 2015
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Nano is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
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ACS Nano
The Deformation of Wrinkled Graphene Zheling Li1, Ian A. Kinloch1, Robert J. Young1*, Kostya S. Novoselov2, George Anagnostopoulos3, John Parthenios3, Costas Galiotis3,4, Konstantinos Papagelis3,5, Ching-Yu Lu6, Liam Britnell6 1
School of Materials and 2School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
3
Institute of Chemical Engineering Sciences, Foundation for Research and Technology – Hellas (FORTH/ ICE-HT), P.O. Box 1414, Patras 26504, Greece, 4
Department of Chemical Engineering and 5Department of Materials Science, University of Patras, Patras 26504, Greece 6
BGT Materials Ltd, Photon Science Institute, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
KEYWORDS: CVD graphene, wrinkles, deformation mechanics, Raman spectroscopy
ABSTRACT
The deformation of monolayer graphene, produced by chemical vapor deposition (CVD), on a polyester film substrate has been investigated through the use of Raman spectroscopy. It has been found that the microstructure of the CVD graphene consists of a hexagonal array of islands
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of flat monolayer graphene separated by wrinkled material. During deformation, it was found that the rate of shift of the Raman 2D band wavenumber per unit strain was less than 25% of that of flat flakes of mechanically-exfoliated graphene, whereas the rate of band broadening per unit strain was about 75% of that of the exfoliated material. This unusual deformation behavior has been modeled in terms of mechanically-isolated graphene islands separated by the graphene wrinkles, with the strain distribution in each graphene island determined using shear lag analysis. The effect of the size and position of the Raman laser beam spot has also been incorporated in the model. The predictions fit well with the behavior observed experimentally for the Raman band shifts and broadening of the wrinkled CVD graphene. The effect of wrinkles upon the efficiency of graphene to reinforce nanocomposites is also discussed.
Following its first isolation in 2004, graphene has shown huge potential in both fundamental studies1 and industrial applications.2 Currently one of the urgent targets is to grow large size, continuous and defect-free graphene. The chemical vapor deposition method (CVD) opens a route to achieve these targets at low cost.3 However, the grain boundaries formed after the graphene grains become stitched together4 affect its performance,5-7 for example, in applications such as transparent electrodes since these boundaries impede electrical transport.4, 8 Moreover, CVD grown graphene typically has to be transferred to other substrates for use,9, 10 during which wrinkles can be induced10, 11 as a result of the different thermal expansion of the substrates,12, 13 the replication of the substrate topography,14 and the transfer process itself.9 These wrinkles have been observed on graphene-based transparent electrodes,15, 16 and are thought to further alter its mechanical stretchability,17 electronic structure,18 and also local potential.19 It is also thought that the presence of wrinkles can affect the deformation of graphene in shear,20 the deformation of graphene oxide paper21 and the ability of graphene oxide to reinforce polymer matrices in
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ACS Nano
nanocomposites.22 Although wrinkling appears to be an inherent property of graphene due to its extremely low bending rigidity23 even when it is fully embedded into polymer matrices,24 there has as yet been no systematic experimental study of its effect upon the mechanical response of graphene. Raman spectroscopy is a versatile tool to study graphene,25-27 in particular, it can be useful in the study of number of layers,25, 28 stacking order28, 29 and doping etc.30, 31 It has also been used to monitor the deformation of graphene,32 and to demonstrate that continuum mechanics is still valid even for a one-atom thick material.24,
33-35
In many of the previous studies on large flat
graphene flakes, it was possible to assume uniformity of the graphene within the spatial resolution of the Raman laser spot (around 1-2 µm in diameter). However, when the graphene is
Article
The Deformation of Wrinkled Graphene Zheling Li, Ian A. Kinloch, Robert J Young, Konstantin S. Novoselov, George Anagnostopoulos, John Parthenios, Costas Galiotis, Konstantinos Papagelis, Ching-Yu Lu, and Liam Britnell ACS Nano, Just Accepted Manuscript • Publication Date (Web): 12 Mar 2015 Downloaded from http://pubs.acs.org on March 13, 2015
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Nano is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
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ACS Nano
The Deformation of Wrinkled Graphene Zheling Li1, Ian A. Kinloch1, Robert J. Young1*, Kostya S. Novoselov2, George Anagnostopoulos3, John Parthenios3, Costas Galiotis3,4, Konstantinos Papagelis3,5, Ching-Yu Lu6, Liam Britnell6 1
School of Materials and 2School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
3
Institute of Chemical Engineering Sciences, Foundation for Research and Technology – Hellas (FORTH/ ICE-HT), P.O. Box 1414, Patras 26504, Greece, 4
Department of Chemical Engineering and 5Department of Materials Science, University of Patras, Patras 26504, Greece 6
BGT Materials Ltd, Photon Science Institute, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
KEYWORDS: CVD graphene, wrinkles, deformation mechanics, Raman spectroscopy
ABSTRACT
The deformation of monolayer graphene, produced by chemical vapor deposition (CVD), on a polyester film substrate has been investigated through the use of Raman spectroscopy. It has been found that the microstructure of the CVD graphene consists of a hexagonal array of islands
ACS Paragon Plus Environment
1
ACS Nano
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
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of flat monolayer graphene separated by wrinkled material. During deformation, it was found that the rate of shift of the Raman 2D band wavenumber per unit strain was less than 25% of that of flat flakes of mechanically-exfoliated graphene, whereas the rate of band broadening per unit strain was about 75% of that of the exfoliated material. This unusual deformation behavior has been modeled in terms of mechanically-isolated graphene islands separated by the graphene wrinkles, with the strain distribution in each graphene island determined using shear lag analysis. The effect of the size and position of the Raman laser beam spot has also been incorporated in the model. The predictions fit well with the behavior observed experimentally for the Raman band shifts and broadening of the wrinkled CVD graphene. The effect of wrinkles upon the efficiency of graphene to reinforce nanocomposites is also discussed.
Following its first isolation in 2004, graphene has shown huge potential in both fundamental studies1 and industrial applications.2 Currently one of the urgent targets is to grow large size, continuous and defect-free graphene. The chemical vapor deposition method (CVD) opens a route to achieve these targets at low cost.3 However, the grain boundaries formed after the graphene grains become stitched together4 affect its performance,5-7 for example, in applications such as transparent electrodes since these boundaries impede electrical transport.4, 8 Moreover, CVD grown graphene typically has to be transferred to other substrates for use,9, 10 during which wrinkles can be induced10, 11 as a result of the different thermal expansion of the substrates,12, 13 the replication of the substrate topography,14 and the transfer process itself.9 These wrinkles have been observed on graphene-based transparent electrodes,15, 16 and are thought to further alter its mechanical stretchability,17 electronic structure,18 and also local potential.19 It is also thought that the presence of wrinkles can affect the deformation of graphene in shear,20 the deformation of graphene oxide paper21 and the ability of graphene oxide to reinforce polymer matrices in
ACS Paragon Plus Environment
2
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ACS Nano
nanocomposites.22 Although wrinkling appears to be an inherent property of graphene due to its extremely low bending rigidity23 even when it is fully embedded into polymer matrices,24 there has as yet been no systematic experimental study of its effect upon the mechanical response of graphene. Raman spectroscopy is a versatile tool to study graphene,25-27 in particular, it can be useful in the study of number of layers,25, 28 stacking order28, 29 and doping etc.30, 31 It has also been used to monitor the deformation of graphene,32 and to demonstrate that continuum mechanics is still valid even for a one-atom thick material.24,
33-35
In many of the previous studies on large flat
graphene flakes, it was possible to assume uniformity of the graphene within the spatial resolution of the Raman laser spot (around 1-2 µm in diameter). However, when the graphene is
