  Graphene covered metal nanoparticles constitute a novel type of hybrid
materials, which provide 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 is 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 to 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.
