Article

Uniform hexagonal graphene flakes and films grown on liquid copper surface.

Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
Proceedings of the National Academy of Sciences (impact factor: 9.68). 04/2012; 109(21):7992-6. DOI:10.1073/pnas.1200339109 pp.7992-6
Source: PubMed

ABSTRACT Unresolved problems associated with the production of graphene materials include the need for greater control over layer number, crystallinity, size, edge structure and spatial orientation, and a better understanding of the underlying mechanisms. Here we report a chemical vapor deposition approach that allows the direct synthesis of uniform single-layered, large-size (up to 10,000 μm(2)), spatially self-aligned, and single-crystalline hexagonal graphene flakes (HGFs) and their continuous films on liquid Cu surfaces. Employing a liquid Cu surface completely eliminates the grain boundaries in solid polycrystalline Cu, resulting in a uniform nucleation distribution and low graphene nucleation density, but also enables self-assembly of HGFs into compact and ordered structures. These HGFs show an average two-dimensional resistivity of 609 ± 200 Ω and saturation current density of 0.96 ± 0.15 mA/μm, demonstrating their good conductivity and capability for carrying high current density.

0 0
 · 
0 Bookmarks
 · 
48 Views
  • Article: Effect of Domain Boundaries on the Raman Spectra of Mechanically Strained Graphene.
    Mark A Bissett, Wataru Izumida, Riichiro Saito, Hiroki Ago
    [show abstract] [hide abstract]
    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.
    ACS Nano 10/2012; 6(11):10229. · 10.77 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.

Keywords

average two-dimensional resistivity
 
chemical vapor deposition approach
 
compact
 
edge structure
 
enables self-assembly
 
grain boundaries
 
greater control
 
large-size
 
low graphene nucleation density
 
single-crystalline hexagonal graphene flakes
 
spatial orientation
 
spatially self-aligned
 
structures
 
underlying mechanisms
 
uniform nucleation distribution
 
uniform single-layered