Synthesis Of One-dimensional Germanium/Graphene Surface Plasmonic Nanostructure And Its Property Tailoring

With the continuous development of optical chip technology,It is an important means to enhance the interaction between light and matter on the nano scale to realize the effective manipulation of photons and the high-speed transmission and processing of optical information.Surface plasmon can break through the traditional optical diffraction limit,and has strong local field enhancement characteristics.It can realize the manipulation and processing of optical signals in nano scale,which makes it have broad application prospects in the fields of high-sensitivity biological detection,sensing and new light sources.However,at present,the research on plasmons is mostly based on precious metals such as gold,silver and so on,and the optical response is usually in the visible and near-infrared bands.For metal,once the type of material,structure and size are determined,its plasmonic wavelength is no longer adjustable,and the metal has high ohmic loss,which is very unfavorable to the propagation of plasmon.For semiconductor materials,they can be doped to achieve higher carrier concentration,so as to realize the tunability of plasmonic wavelength.As a two-dimensional semi metallic material,graphene has ultra-high carrier mobility and wide response band,and it can excite highly localized surface plasmons.At the same time,the Fermi level of graphene can be adjusted by chemical doping and bias voltage to realize the tunability of graphene plasmonic frequency.At present,graphene based plasmonic nanostructures are mostly integrated with other precious metal materials which prepared rely on transfer.However,the pollution and damage will be introduced in the process of transfer,which will directly affect the mobility of graphene carriers,and then affect its plasmonic lifetime.Moreover,photoresist is often used in the process of processing into devices,which will also affect the quality of devices.In view of the above problems,this paper takes graphene based plasmonic nanostructure as the research object,skillfully combines graphene and semiconductor and designs a new type of one-dimensional plasmonic nanostructure,and carries out the research on the preparation and performance regulation of high-quality graphene based plasmonic nanostructures,so as to provide a feasible idea for the development of graphene based plasmon nanostructures.The main research contents are as follows:(1)The preparation of one-dimensional germanium / graphene(Ge-Gr)plasmonic nanostructure.As a new semiconductor plasmon material,Ge has an adjustable mid infrared plasmon effect similar to graphene,and its loss is low.Through the ingenious combination of Ge and graphene,a new plasmonic nanostructure is constructed to enhance the coupling of the two plasmons.The specific work is to grow single crystal Ge nanowires(Ge NWs)in a high-temperature tubular furnace by chemical vapor deposition,and then prepare high-quality graphene on the surface of Ge NWs by changing gas carbon source and temperature in the same system.In this experiment,one-dimensional plasmonic nanostructures were directly constructed by two-step in-situ growth,which avoided the plasmon attenuation caused by the pollution of graphene caused by the transfer process.The morphology and crystal quality of graphene and NWs were characterized by Electron Microscopy,Raman spectroscopy,Atomic Force Microscopy and other testing techniques.The results show that the prepared Ge NWs has a single crystal structure,the external surface of Ge NWs is very smooth and pollution-free,and the graphene grown on the surface of Ge NWs has high crystallinity,which indicates that the controllable preparation of one-dimensional Ge-Gr plasmonic nanostructures has been realized.(2)Performance regulation of one-dimensional Ge-Gr plasmonic nanostructure.For the regulation of the properties of one-dimensional plasmonic nanostructures,the plasmon is regulated by the diameter and doping of Ge NWs.In the experiment,Ge NWs with different diameters were prepared by designing the size of catalyst particles and growth temperature,and Ge NWs with high carrier concentration were prepared by adjusting the amount of doping source.The finite difference time domain(FDTD)theory is used to simulate the plasmonic response of Ge NWs with different diameters and carrier concentrations.The near field optical imaging of the Ge NWs and the one-dimensional Ge-Gr plasmonic nanostructure was carried out to verify the plasmonic response by Scanning Near-field Optical Microscope(SNOM).The selectivity of CEMS(2-chloroethyl methyl sulfide)and PDMS(polymethyl methacrylate)was enhanced by Fourier Transform Infrared Spectrometer(FTIR).This study provides an effective way for in-situ fabrication of low-dimensional graphene based plasmonic nanostructures and a new idea for the development of on-chip integrated high-sensitivity graphene optoelectronic devices.