Nanoscale electronic and optical investigations of functionalized graphene

A rigorous understanding of light-matter interactions at the nanometer scale is pivotal in the development of nanoscale device applications. Graphene and its functionalized derivatives, due to their unique properties, promise unexpected capabilities as a platform for such devices, which has led to significant interest in graphene-based nano-optical, optoelectronic, and photovoltaic applications. Here, we will describe our efforts to resolve and understand the structural, electronic and optical properties of these systems. We will present a UHV STM study of the structural and electronic properties of C60 molecules deposited on graphene that was grown epitaxially on SiC(0001), which serves as a model system for the study of molecule-surface interactions. Our results indicate reduced coupling of the molecules to the graphene and underlying substrate, compared to those on metallic substrates, suggesting a path for developing molecular-scale electronic and optically active ``devices'' that are not dominated by the substrate. We will also discuss our efforts to correlate these STM studies with the optical properties of the system using a UHV STM that incorporates confocal optical microscopy and spectroscopy at the tip-sample junction with integrated high-numerical aperture optics.