Electromagnetic Field Distribution In Metal Nanoparticle Dimer On Graphene

In recent years,due to its excellent optical and electrical properties,graphene has attracted considerable interest.And graphene plasmonics has also developed rapidly.In the ongoing search for new and better plasmonic materials,graphene has emerged to be a very promising candidate for mid-infrared and infrared applications.In addition,the study of surface plasmon of metal nanoparticles is also a hot topic in the world.Thus,the overlap field of graphene plasmonics and metal plasmonics have been an important subregion in the photonics research.Not only does graphene possess intrinsic plasmons that are tunable and adjustable,but a combination of graphene with noble-metal nanostructures promises a variety of exciting applications for conventional plasmonics.The versatility of graphene means that graphene-based plasmonics may enable the manufacture of novel optical devices working in different frequency ranges,from visible to the infrared.Graphene has Raman signal,and the enhancement of electromagnetic field generated by plasmon is also the main reason for surface enhanced Raman scattering.Therefore,the study of the surface enhanced Raman scattering(SERS)of the hybrid system of graphene and metal nanoparticles has also become an important application field in the study of the hybrid system.This paper is mainly based on the hybrid system of metal nanoparticles and graphene.By changing the excitation wavelength of the system,the redistribution of the electric field in the hybrid system is studied from the visible to infrared wavelengths.First,the electromagnetic field distribution of Ag nanoparticle monomer and Ag nanoparticle dimmer on monolayer graphene was studied by finite difference time domain method.Because of the dielectric properties of graphene in the visible region and the semimetal properties in the infrared region,the electromagnetic field(EM)redistribution occurs in the infrared region.When the infrared laser is excited,the enhancement of the strongest electric field in the infrared region is mainly distributed in the gap between the silver nanoparticles and the monolayer graphene,and the light energy is also restricted to the surface of the monolayer graphene.Secondly,we use the surface charge distribution of hybrid system and surface enhanced Raman spectroscopy(SERS)to confirm this phenomenon.In addition,the distribution of the electric field of the hybrid system formed by the dielectric nanoparticles and the monolayer graphene at the infrared wavelength indicates that the redistribution of the electric field is due to the coupling of the mirror charge of the surface of the dielectric nanoparticles on the surface of the monolayer graphene surface excited by the light and the surface of the graphene.In addition,we also studied the electric field redistribution of two and multilayer graphene hybrid systems,but the two and multilayered graphene did not show the excellent performance of the monolayer graphene in the hybrid system.Therefore,further research on two-and multilayer graphene will be carried out in the future work.Our work extends the knowledge of single-layer graphene plasma,which is widely used in graphene related research.