Why Multilayer Graphene on 4 H − SiC ( 000 1 ¯ ) Behaves Like a Single Sheet of Graphene
The Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA.Physical Review Letters (Impact Factor: 7.51). 03/2008; 100(12):125504. DOI: 10.1103/PhysRevLett.100.125504
We show experimentally that multilayer graphene grown on the carbon terminated SiC(0001[over ]) surface contains rotational stacking faults related to the epitaxial condition at the graphene-SiC interface. Via first-principles calculation, we demonstrate that such faults produce an electronic structure indistinguishable from an isolated single graphene sheet in the vicinity of the Dirac point. This explains prior experimental results that showed single-layer electronic properties, even for epitaxial graphene films tens of layers thick.
- "This kind of information is of great interest because one can expect that at a certain rotational misorientation, MLG has charge transfer properties similar to SLG with massless fermions . The SLG-like behavior has been demonstrated for the rotationally faulted MLG grown on C-terminated face of SiC   where up to 8 adjacent graphene layers were rotated by a certain angle relatively to each other . For epitaxial graphene on C-face of SiC, the graphite-like (Bernal or ABstacking ng is not usual. "
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- "The increased interlayer spacing between graphene planes brings about weakening of the interlayer interactions which further induces electronic decoupling of the layers, as is also the case of non-Bernal stacked, multi-layer graphene grown on the C-face of SiC   . The appearance of Dirac-like electronic states in multilayer C-face, rotationally faulted graphene, is the origin of enhanced transport properties, which are comparable to those of the single layer graphene   . "
ABSTRACT: Production of graphene-based structures and composites can be achieved in a number of ways using predominantly chemical-vapor-deposition-based approaches and solution chemistry methods. The present work investigates the feasibility of infrared lasers in the controlled graphitization of micron-sized SiC particles. It is demonstrated that laser-mediated SiC decomposition can result in a manifold of graphene structures depending on the irradiation conditions. In particular, graphene formation, at nearly ambient conditions, can take place in various forms resulting in SiC particles covered by few-layer epitaxially grown films, and particles with a progressively increasing thickness of the graphitized layer, reaching eventually to free-standing 3D graphene froths at higher irradiation doses. Electron microscopies are used to determine the graphene layer features while Raman scattering identifies high-quality, strain-free graphene. Implications of graphene-coated particles and 3D porous graphene scaffolds to a variety of applications are briefly discussed. The present findings testify the potential of lasers toward the tailor-made preparation of high-quality graphene-based structures. The scalability and adaptability of lasers further support their prospect to develop reliable, reproducible, eco-friendly and cost-effective laser-assisted graphene production technologies.
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- "Despite significant progress in technological advancement in graphene growth on SiC substrates there are still some barriers to overcome such as instability of silicon sublimation, carbon surface diffusion, polycrystalline nature of graphene layer and influence of step edges, among others   . The growth of graphene on SiC by Si sublimation is a bottom-up process, in which carbon atoms are supplied from the substrate . "
ABSTRACT: The initial stage of the growth of graphene on SiC with the underlying mechanism of carbon layer early stage formation on the single crystal silicon carbide surface was studied using silicon sublimation technique. The obtained buffer layer is organized in a form of carbon regions with 10% of sp3 defects separated 10–15 Å. Raman spectroscopy was used to assess the degree of the buffer layer’s disorder. The intensity of I(D) and I(GB) buffer peaks was found to be proportional to the number of defects. Although the layer is not fully saturated with carbon atoms, it remains impenetrable. However, sublimation from the steps side walls which are not covered by the buffer layer is possible. It was observed that in the vicinity of the macro-step edges the sublimation is more effective, which leads to the production of additional free C atoms, filling the buffer layer structure, subsequently decreasing sp3 hybridization, to about 1–2%. This healing process which also continues during the graphene layer growth is reflected in a decrease in D line intensity and finally in formation of the well-organized buffer layer.
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