Effect of gap modes on graphene and multilayer graphene in tip-enhanced Raman spectroscopy.

The experimental system formed by an electrochemically etched Au tip and an Au substrate is studied in a tip-enhanced Raman spectroscopy (TERS) setup with side illumination. A resonant optical cavity is created allowing the interaction between localized surface plasmons (LSPs) from the tip and surface plasmon polaritons (SPPs) from the substrate, the so called 'gap modes'. We investigate the interaction between multilayer graphene and gap modes as well as localized emission of defects and inner unknown molecules enhanced by this coupling. The effect of this intense localized electromagnetic field is also studied on monolayer graphene deposited on SiO2. [ABSTRACT FROM AUTHOR]