ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
In this work, carbon nanotube samples were produced by aerosol chemical vapour deposition from a solution of ferrocene in benzylamine. The multi-walled nanotubes produced by this method were investigated by TEM, SEM/EDS, scanning tunneling microscopy (STM) and tunneling spectroscopy (STS). The dl/dV curves obtained from the STS measurements showed asymmetric density of states (DOS) in nanotubes, with higher DOS above the Fermi energy. These STS measurements and the EDS analysis indicate successful doping with nitrogen originating from the decomposition of benzylamine.