Surface-Enhanced Raman Spectroscopy of Graphene

Abstract

Surface-enhanced Raman scattering (SERS) exploits surface plasmons induced by the incident field in metallic nanostructures to significantly increase the Raman intensity. Graphene provides the ideal prototype two-dimensional (2d) test material to investigate SERS. Its Raman spectrum is well-known, graphene samples are entirely reproducible, height controllable down to the atomic scale, and can be made virtually defect-free. We report SERS from graphene, by depositing arrays of Au particles of well-defined dimensions on a graphene/SiO(2) (300 nm)/Si system. We detect significant enhancements at 633 nm. To elucidate the physics of SERS, we develop a quantitative analytical and numerical theory. The 2d nature of graphene allows for a closed-form description of the Raman enhancement, in agreement with experiments. We show that this scales with the nanoparticle cross section, the fourth power of the Mie enhancement, and is inversely proportional to the tenth power of the separation between graphene and the center of the nanoparticle. One important consequence is that metallic nanodisks are an ideal embodiment for SERS in 2d.

Dipole-dipole interaction between a quantum dot and a graphene nanodisk

“…Graphene has also been recognized as a useful optical material for novel photonic and optoelectronic applications. [20][21][22][23][24][25] For these reasons, the study of plasmonics in graphene has received significant attention both experimentally and theoretically. 21,22,[26][27][28][29] Recently, experimental research on graphene has been extended to the fabrication and study of QD-graphene nanostructures.…”

“…[20][21][22][23][24][25] For these reasons, the study of plasmonics in graphene has received significant attention both experimentally and theoretically. 21,22,[26][27][28][29] Recently, experimental research on graphene has been extended to the fabrication and study of QD-graphene nanostructures. [30][31][32][33][34] For example, a CdS QD-graphene hybrid system has been synthesized by Cao et al, 30 in which a picosecond ultrafast electron transfer process from the excited QD to the graphene matrix was observed using time-resolved fluorescence spectroscopy.…”

“…Metal nanoparticlegraphene hybrid systems have also been fabricated by several groups. 21,[35][36][37] Here, we study a QD-graphene hybrid system, where energy transfer occurs due to the interaction between optical excitations in the QD and graphene nanodisk. The optical excitations in the QD are excitons, which are electron-hole pairs, while those in the graphene nanodisk are surface plasmon polaritons, which are created due to the collective oscillations of conduction-band electrons.…”

Surface Plasmon Polariton Graphene Photodetectors

“…LSPRs originate from the resonant coherent oscillation of the metal's conduction electrons in response to the incident radiation. The resulting enhanced near-fields surrounding the nanostructures promote light absorption in the materials around them [44]. We previously reported a ×20 enhancement in photoresponse [9] when radiation is focused close to the nanostructures.…”

“…The dielectric functions of Au [62] and graphene [63] are treated through a Drude-Lorentz model, as explained in Ref. [44] and in Methods. Inserting Au's dielectric function in Eqs.1,2, with ǫ d =1 for air, yields λ 0 =645nm for the vacuum wavelength of the SPPs on the Au/air interface.…”