Preparation And Properties Of The Doped Graphene Based Photodetector

Graphene is a kind of two-dimensional material which composed of sp²-hybrided carbon packed into honeycomb lattice.Graphene has attracted much attention because of its unique physical properties such as ambipolar electric field effect,high mobility of charge carriers?200,000 cm²/V·s?,anomalous quantum Hall effect?QHE?and massless relativistic carriers.Since Novoselov and Geim found the graphene and prepared the first graphene field-effect transistor?GFET?in 2004.However,intrinsic graphene has a zero bandgap and is therefore a semi-metal,the energy band of graphene can be easily opened by the following methods,such as a biased voltage,surface adsorbed molecules,substituted atoms and quantum confinement effect which may lead to the Fermi Level shift relative to the Dirac point.In this thesis,we have studied the preparation,properties and application of melamine doped bilayer graphene and chlorine doped graphene quantum dots in photodetectors.The prepared doped graphene-based materials and devices were characterized by atomic force microscopy?AFM?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,scanning electron microscopy?EDS?,X-ray diffraction?XRD?,X-ray photoelectron spectroscopy,UV-Vis-NIR,PL-PLE,Raman spectroscopy,Keithley 2400 and field-effect test system.The specific research contents and conclusions are as follows:1.The liquid paraffin and chloroform as the carbon source and the chlorine source respectively,we use a facile co-combustion method?T-X-J method?,which combines the techniques of simple batch synthesis and heteroatom doping in one single step for the preparation of Cl-GQDs with the typical diameter of 3.3 nm,The doping concentration of chlorine in Cl-GQDs can be adjusted easily by varying the mass of chloroform in the source.The morphologies,optical and electrical properties of Cl-GQDs were characterized.Meanwhile,a nanocomposite of Cl-GQDs and ZnO QDs has been achieved by chemical route which was then used as the photo-active material.The vertical photodetectors based on Cl-GQDs have been fabricated and shows an excellent performance for light response from 365 to 650 nm,the responsivity and detectivity of photodetectors based on Cl-GQDs as high as 15.13 A/W and 1.3×10¹³ Jones were achieved at 2V bias voltage under the light of 650 nm respectively.And the chlorine-doped graphene quantum has better performance than the graphene quantum dot.2.The highly quality monolayer and bilayer graphene were prepared by CVD method.The controlled growth conditions of monolayer and bilayer graphene have been studied,and the photoelectric properties of bilayer graphene doped with melamine on the surface were further studied.Melamine doping bilayer graphene field-effect transistor UV detector was also prepared,the melamine surface doping of the graphene was further studied.The results of the photoelectric tests show that the graphene prepared by the traditional method exhibits strong p-type conductivity due to the remaining PMMA on the surface in the process of transfer,and the FETs results measured in the air indicate that the electrical conducting of bilayer graphene may be tuned from a strong p type to a weak p type after doping with melamine.The responsivity and detectivity of photodetectors based on melamine surface doping of the bilayer graphene as high as 96A/W and 10¹² Jones were achieved under the light of 365 nm respectively,which indicated the direction of graphene n-type doping and laid the foundation for the construction of graphene p-n junction photodetector.