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Palinkas A.,Institute of Technical Physics and Materials Science | Palinkas A.,Korea Hungary Joint Laboratory for Nanosciences KHJLN | Sule P.,Institute of Technical Physics and Materials Science | Szendro M.,Institute of Technical Physics and Materials Science | And 7 more authors.
Carbon | Year: 2016

Graphene-metal nanoparticle hybrid materials potentially display not only the unique properties of metal nanoparticles and those of graphene, but also additional novel properties due to the interaction between graphene and nanoparticles. This study shows that gold nanoislands can be used to tailor the local electronic properties of graphene. Graphene on crystalline gold nanoislands exhibits moiré superlattices, which generate secondary Dirac points in the local density of states. Conversely, the graphene covered gold regions undergo a polycrystalline → Au (111) phase transition upon annealing. Moreover, the nanoscale coexistence of moiré superlattices with different moiré periodicities has also been revealed. Several of these moiré periodicities are anomalously large, which cannot be explained by the standard lattice mismatch between the graphene and the topmost Au (111) layers. Density functional theory and molecular dynamics simulations show for the first time that in such cases the graphene and the interfacial metallic layer is strained, leading to distorted lattice constants, and consequently to reduced misfit. Room temperature charge localization induced by a large wavelength moiré pattern is also observed by scanning tunneling spectroscopy. These findings can open a route towards the strain engineering of graphene/metal interfaces with various moiré superlattices and tailored electronic properties for nanoscale information coding. © 2016 Elsevier Ltd Source


Osvath Z.,Institute of Technical Physics and Materials Science | Osvath Z.,Korea Hungary Joint Laboratory for Nanosciences KHJLN | Deak A.,Institute of Technical Physics and Materials Science | Kertesz K.,Institute of Technical Physics and Materials Science | And 8 more authors.
Nanoscale | Year: 2015

Graphene covered metal nanoparticles constitute a novel type of hybrid material, which provides a unique platform to study plasmonic effects, surface-enhanced Raman scattering (SERS), and metal-graphene interactions at the nanoscale. Such a hybrid material is fabricated by transferring graphene grown by chemical vapor deposition onto closely spaced gold nanoparticles produced on a silica wafer. The morphology and physical properties of nanoparticle-supported graphene are investigated by atomic force microscopy, optical reflectance spectroscopy, scanning tunneling microscopy and spectroscopy (STM/STS), and confocal Raman spectroscopy. This study shows that the graphene Raman peaks are enhanced by a factor which depends on the excitation wavelength, in accordance with the surface plasmon resonance of the gold nanoparticles, and also on the graphene-nanoparticle distance which is tuned by annealing at moderate temperatures. The observed SERS activity is correlated with the nanoscale corrugation of graphene. STM and STS measurements show that the local density of electronic states in graphene is modulated by the underlying gold nanoparticles. This journal is © The Royal Society of Chemistry 2015. Source


Osvath Z.,Institute of Technical Physics and Materials Science | Osvath Z.,Korea Hungary Joint Laboratory for Nanosciences KHJLN | Gergely-Fulop E.,Institute of Technical Physics and Materials Science | Nagy N.,Institute of Technical Physics and Materials Science | And 9 more authors.
Nanoscale | Year: 2014

The electronic properties of graphene can be significantly influenced by mechanical strain. One practical approach to induce strain in graphene is to transfer atomically thin membranes onto pre-patterned substrates with specific corrugations. The possibility of using nanoparticles to impart extrinsic rippling to graphene has not been fully explored yet. Here we study the structure and elastic properties of graphene grown by chemical vapour deposition and transferred onto a continuous layer of SiO2 nanoparticles with diameters of around 25 nm, prepared on a Si substrate by the Langmuir-Blodgett technique. We show that the corrugation of the transferred graphene, and thus the membrane strain, can be modified by annealing at moderate temperatures. The membrane parts bridging the nanoparticles are suspended and can be reversibly lifted by the attractive forces between an atomic force microscope tip and graphene. This allows the dynamic control of the local morphology of graphene nanomembranes. © 2014 the Partner Organisations. Source


Osvath Z.,Institute of Technical Physics and Materials Science | Osvath Z.,Korea Hungary Joint Laboratory for Nanosciences KHJLN | Vertesy Z.,Institute of Technical Physics and Materials Science | Vertesy Z.,Korea Hungary Joint Laboratory for Nanosciences KHJLN | And 7 more authors.
Thin Solid Films | Year: 2014

Graphitic nanodisks of typically 20-50 nm in thickness, produced by the so-called Kvaerner Carbon Black and Hydrogen Process were dispersed on gold substrate and investigated by atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and confocal Raman spectroscopy. The roughness of the gold surface was drastically changed by annealing at 400 °C. AFM measurements show that this change in the surface roughness induces changes also in the topography of the nanodisks, as they closely follow the corrugation of the gold substrate. This leads to strained nanodisks, which is confirmed also by confocal Raman microscopy. We found that the FE-SEM contrast obtained from the disks depends on the working distance used during the image acquisition by In-lens detection, a phenomenon which we explain by the decrease in the amount of electrons reaching the detector due to diffraction. This process may affect the image contrast in the case of other layered materials, like hexagonal boron nitride, and other planar hybrid nanostructures, too. © 2014 Elsevier B.V. All rights reserved. Source

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