Research On Propagation Surface Plasmon Polaritons Of Ag Nanowire-MoS₂(Graphene) Hybrid Structure

Surface plasmas can limit light to subwavelength space size,and have large bandwidth to process and transmit information.Therefore,they are of great significance for the development of micro-nano optoelectronic integration.It is well known that optical waveguide is the basic device of optoelectronic integration.Among them,metal silver nanowire(Ag NWs)can use their surface plasmon polaritons(SPPs)to coupling the external light into the nanowires and tightly bound to the metal surface for propagation.At the same time,the plasma waveguide has attracted more and more attention because its SPPS has the characteristics of easy excitation and low loss.In recent years,two-dimensional materials have attracted wide attention due to their excellent photoelectric properties.The composite of precious metal SPPs with two-dimensional materials has brought many new phenomena and achievements in different fields of optoelectronics,such as surface-enhanced Raman scattering biosensor solar cells and photocatalysis.Among them,graphene has a unique electronic structure,its Fermi level can be changed with the bias voltage.Monolayer molybdenum disulfide has a natural direct band gap,which makes up for the deficiency of graphene and shows great advantages in nanophotonic circuits.Therefore,the composite structure of Ag and monolayer molybdenum disulfide(graphene)will be designed in this paper.It is attempted to adjust the propagation performance of Ag SPPs by means of applied electric field,morphology and thickness design by taking advantage of the excellent photoelectric properties of two-dimensional materials and their dielectric constant.The main contents include:(1)Preparation and characterization of Ag NWs and two-dimensional molybdenum disulfide.Ag NWs with smooth surface and good morphology was prepared by polyol reduction method.Then,on the basis of polyol reduction method,using dilute nitric acid to treat the inner lining of autoclave and seed method to prepare nanowires with larger diameter,whose diameter can be adjusted from 100 nm to 1000 nm.In addition,high quality and good reproducible triangular monolayer molybdenum disulfide with side length up to 30?m was prepared by CVD method at atmospheric pressure and 300 Torr pressure.(2)Research on SPPs propagation of Ag/monolayer molybdenum disulfide hybrid structure.The excitation efficiency and propagation efficiency of Ag nanowires on silica and molybdenum disulfide/silica substrates were compared and studied by using near field excitation method of fiber taper under optical microscope.Finite element analysis was used to model and analyze the structure,and the SPPs electric field distributions at the ends of the two substrates at the same wavelength were compared.The electric field distribution of SPPs in H₀,H₁,H₂mode of Ag NW and the relationship between the transmission length and the diameter of Ag NW were analyzed.The experimental results show that regardless of the diameter of Ag NW,with the help of Mo S₂,the SPPs propagation length of Ag NWs can be increased.(3)Study on SPPs propagation of Ag/graphene hybrid structure.A silicon dioxide film was coated on the Ag nanowires by STOBE method.The SPPs propagation behavior of the silica coated Ag nanowires and the bare Ag nanowires on the silica substrate was compared by the near field excitation of the optical fiber taper.We found that Ag nanowires coated with silica were more likely to excite SPPs.Then,the electric field distribution of surface plasmon H₀,H₁and H₂on silica,molybdenum disulfide/silica and graphene/silica substrates and the relationship between the propagation length and the diameter of Ag nanowires were analyzed.Finally,a graphene-based device structure was designed,and the regulation effect of different bias voltages on SPPs transmission of Ag nanowires was verified through experiments.