Evidence of plasmonic coupling in gallium nanoparticles/graphene/SiC

Graphene is emerging as a promising material for plasmonics applications due to its strong light-matter interactions, most of which are theoretically predicted but not yet experimentally realized. Therefore, the integration of plasmonic nanoparticles to create metal nanoparticle/graphene composites enables numerous phenomena important for a range of applications from photonics to catalysis. For these applications it is important to articulate the coupling of photon-based excitations such as the interaction between plasmons in each of the material components, as well as their charge-based interactions dependent upon the energy alignment at the metal/graphene interface. These coupled phenomena underpin an active application area in graphene-based composites due to nanoparticle-dependent surface-enhanced Raman scattering (SERS) of graphene phonon modes. This study reveals the coupling of a graphene/SiC support with Ga-nanoparticle-localized surface plasmon resonance, which is of particular interest due to its ability to be tuned across the UV into the near-IR region. This work is the first demonstration of the evolving plasmon resonance on graphene during the synthesis of surface-supported metal nanoparticles, thus providing evidence for the theoretically predicted screening revealed by a damped resonance with little energy shift. Therefore, the role of the graphene/substrate heterojunction in tailoring the plasmon resonance for nanoplasmonic applications is shown. Additionally, the coupled phenomena between the graphene-Ga plasmon properties, charge transfer, and SERS of graphene vibrational modes are explored.