Subscriber access provided by The Libraries of the | University of North Dakota
Article
Requirement on Aromatic Precursor for Graphene Formation Kati Gharagozloo-Hubmann, Niclas Sven Mueller, Michael Giersig, Christian Lotze, Katharina J Franke, and Stephanie Reich J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.6b01781 • Publication Date (Web): 15 Apr 2016 Downloaded from http://pubs.acs.org on April 17, 2016
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.
The Journal of Physical Chemistry C 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.
Page 1 of 14
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
The Journal of Physical Chemistry
Requirement on Aromatic Precursor for Graphene Formation K. Gharagozloo-Hubmann,1* N. S. Müller,1 M. Giersig,1 C. Lotze,1 K. J. Franke1 and S. Reich1 1
Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
ABSTRACT We studied graphene growth from solid, aromatic precursors at low temperature (~400°C) on a metal surface via high vacuum (6 •10-6 mbar) chemical vapor deposition. A set of conjugated and condensed aromatic precursor molecules, i.e., structural isomers of terphenyl and anthracene are compared. While para-terphenyl (p-terphenyl) and meta-terphenyl (m-terphenyl) were found to be excellent precursors for the formation of graphene, no graphene was obtained from orthoterphenyl (o-terphenyl) or anthracene. We propose a reaction mechanism that explains the differing growth products. The key requirement for the synthesis of graphene is a three-dimensional nature and suitable molecular structure of the precursor. Its incorporation into a flat aromatic system on a metal surface has to provide sufficient energy gain for the polymerization to occur.
INTRODUCTION Graphene, an isolated layer from graphite, is a prominent example of an organic material with enormous potential for versatile applications. The properties of graphene can be widely tuned through nanostructuring, e.g., the electrical and optical properties of the nanometer-wide graphene stripes depend on the width of the structures (bandwidth) and the configurations of the edge atoms1,2. After its discovery in 20043, many studies focused on the production of graphene. Top-down as well as bottom-up - paths were studied extensively. Bottom-up methods are promising for large area graphene growth and the industrial production4,5 of graphene. Chemical vapor deposition (CVD) is frequently employed for the bottom-up synthesis of graphene islands and continuous films from molecular building blocks on transition metal surfaces.4,6,7 Common molecular building blocks for graphene synthesis are the gases methane6, ethene8 and ethyne9. CVD typically uses gaseous feedstock, since gas flow- and pressure are widely controllable. Many studies dealt with the influence of these process parameters on the graphene layers. The influence of pressure on the shape and the size of graphene was discussed10,11 and substrate effects were investigated.12 A major drawback of employed gaseous precursors is the high temperature (over 850°C) that is required for the CVD process. This leads to a long process time and eventually sublimation of metal atoms from the surface of the catalyst.
ACS Paragon Plus Environment
The Journal of Physical Chemistry
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
Page 2 of 14
Liquid and solid precursor molecules were originally rarely used for graphene synthesis, although their adsorption is energetically favored on a metal substrate13. First attempts to synthesize graphene from solid precursors were published by Sun et al.14. They used polymer films such as poly methyl methacrylate (PMMA) and styrene. However, the temperature for the conversion of the PMMA film to graphene (800°C) was comparable to the temperature for CVD from gas molecules. First, the decomposition of the polymer into unsaturated hydrocarbon molecules occurred, which starts at 300°C for PMMA15,16. The subsequent growth process was therefore similar to conventional CVD with gaseous precursors. Another approach is the use of halogen-substituted aromatic precursors. They are excellent building blocks for self-assembled layers. Their polymerization into graphene sub-structures at low temperature (
