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Author: Rümmeli, Mark × Type: article × Publisher: London : Nature Publishing Group × search.filters.applied.f.series: Scientific Reports, Volume 3 ×

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    CVD growth of large area smooth-edged graphene nanomesh by nanosphere lithography
    (London : Nature Publishing Group, 2013) Wang, Min; Fu, Lei; Gan, Lin; Zhang, Chaohua; Rümmeli, Mark; Bachmatiuk, Alicja; Fang, Ying; Liu, Zhongfan
    Current etching routes to process large graphene sheets into nanoscale graphene so as to open up a bandgap tend to produce structures with rough and disordered edges. This leads to detrimental electron scattering and reduces carrier mobility. In this work, we present a novel yet simple direct-growth strategy to yield graphene nanomesh (GNM) on a patterned Cu foil via nanosphere lithography. Raman spectroscopy and TEM characterizations show that the as-grown GNM has significantly smoother edges than post-growth etched GNM. More importantly, the transistors based on as-grown GNM with neck widths of 65-75 nm have a near 3-fold higher mobility than those derived from etched GNM with the similar neck widths.
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    High-mobility graphene on liquid p-block elements by ultra-low-loss CVD growth
    (London : Nature Publishing Group, 2013) Wang, Jiao; Zeng, Mengqi; Tan, Lifang; Dai, Boya; Deng, Yuan; Rümmeli, Mark; Xu, Haitao; Li, Zishen; Wang, Sheng; Peng, Lianmao; Eckert, Jürgen; Fu, Lei
    The high-quality and low-cost of the graphene preparation method decide whether graphene is put into the applications finally. Enormous efforts have been devoted to understand and optimize the CVD process of graphene over various d-block transition metals (e.g. Cu, Ni and Pt). Here we report the growth of uniform high-quality single-layer, single-crystalline graphene flakes and their continuous films over p-block elements (e.g. Ga) liquid films using ambient-pressure chemical vapor deposition. The graphene shows high crystalline quality with electron mobility reaching levels as high as 7400 cm2 V−1s−1 under ambient conditions. Our employed growth strategy is ultra-low-loss. Only trace amounts of Ga are consumed in the production and transfer of the graphene and expensive film deposition or vacuum systems are not needed. We believe that our research will open up new territory in the field of graphene growth and thus promote its practical application.
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    Microscopic insight into the bilateral formation of carbon spirals from a symmetric iron core
    (London : Nature Publishing Group, 2013) Shiozawa, Hidetsugu; Bachmatiuk, Alicja; Stangl, Andreas; Cox, David C.; Silva, S. Ravi P.; Rümmeli, Mark; Pichler, Thomas
    Mirrored carbon-spirals have been produced from pressured ferrocene via the bilateral extrusion of the spiral pairs from an iron core. A parametric plot of the surface geometry displays the fractal growth of the conical helix made with the logarithmic spiral. Electron microscopy studies show the core is a crystalline cementite which grows and transforms its shape from spherical to biconical as it extrudes two spiralling carbon arms. In a cross section along the arms we observe graphitic flakes arranged in a herringbone structure, normal to which defects propagate. Local-wave-pattern analysis reveals nanoscale defect patterns of two-fold symmetry around the core. The data suggest that the bilateral growth originates from a globular cementite crystal with molten surfaces and the nano-defects shape emerging hexagonal carbon into a fractal structure. Understanding and knowledge obtained provide a basis for the controlled production of advanced carbon materials with designed geometries.