ZnO/Graphene Nano-composite Materials:Synthesized,Photoluminescence And Electrical Performance

With the miniaturization of electronic equipment,the structure has become more compact.As a result,it is very effective to apply new functional material,such as two-dimensional Graphene,Graphene composite materials and zinc oxide(ZnO)composite materials to produce small,micro,and super-micro devices.Especially,it is shown that the ZnO/Graphene nano-composite materials perform very well in the fields of the UV detector,field effect transistor,photoelectric devices and dye-sensitised cells,field emission cathode areas,having a promising prospect for future application.Based on such background,the graphene films will be synthesized and directly grown on the substrate using chemical vapor deposition(CVD)and then the ZnO thin films will be deposited on Graphene films by magnetron sputtering method.In this process,the graphene films is used as the buffer layer between ZnO and substrate materials,so the ZnO/Graphene composite film materials will be obtained and their optical performance will be studied.Whereafter,the ZnO nanorod arrays will further grow on ZnO/Graphene composite film by hydrothermal method,and their field emission performances will be studied.Finally,on this basis,the improved field emission performance of composite material will further be studied by the doping of metal ion.Their measurement and characterization will be carried out respectively by the Raman spectra,scanning electron microscope,X-ray photoelectron spectroscopy,X-Ray Diffraction,Photoluminescence spectrum,Transmission electron microscope,and field emission tester.The main research contents are as follows:(1)Using orthogonal experiments,the Graphene films are prepared with copper(Cu)as catalytic substrate using chemical vapor deposition(CVD).The orthogonal polar difference analysis is employed on the Raman test results of as-prepared graphene film samples to ameliorate the preparation of process parameters.Finally,it is found that at the optimal process parameters of chemical vapor deposition(CH4 flows:10 sccm,CH4:H2:1/10,deposition temperature:1000 ?,reaction time:5 min),the controllable graphene films of the large area,high crystallization quality,low defect density and less layers are successfully prepared(chapter 3).(2)Using single factor experiments,ZnO and ZnO/Graphene composite films are deposited on Cu substrate using the magnetron sputtering method.By comparing the results and analysis of their structure,morphology,deposition rate,deposition mechanism and chemical bonding,it is proved that using Graphene as a buffer layer can improve the crystal quality of ZnO thin film.Finally,it is found that at the optimal parameters of magnetron sputtering process(substrate temperature:30 ?,power:350 W,working pressure:6.5 Pa,Ar:O2:40/10 sccm,annealing temperature:500 ?),the controllable ZnO/Graphene composite films of the higher crystallization quality are successfully prepared(chapter 4).(3)Using single factor experiments,ZnO nanorods arrays are synthesized on the ZnO/Graphene composite thin film by hydrothermal method,and their structure,morphology,optical and field emission performances are analyzed.Finally,it is found that at the optimal parameters of hydrothermal process(reaction temperature:100 ?,[OH-]/[Zn2+]:22,Zn2+concentration:0.02 mol/L,reaction time:180 min),the controllable and higher crystallization quality ZnO/Graphene nanorods arrays are successfully prepared.According to the XPS characterization analysis,the growth mechanism is studied and it is further identified that the field emission properties of ZnO nanorods arrays have improved in the case of Graphene as a buffer layer.The turn-on field is 1.93 V/?m and the field enhancement factor is 9540(chapter 5).(4)Using doping experiments,the Al doped,Cu doped and Ba doped ZnO nanorods array s are synthesized by introducing the concentrations of 0%?2%?4%?6%?8%using hydrothermal method,and their structure and morphology are characterized by XRD,EDS and SEM,XPS,PL.Finally,the field emission performances of Al:6%doped,Cu:4%doped and Ba:2%doped ZnO nanorods arrays are measured.The turn-on field and field enhancement factor of Al:6%doped ZnO nanorods arrays are 1.51 V/?m and 11264.The turn-on field and field enhancement factor of Cu:4%doped ZnO nanorods arrays are 1.80 V/?m and 10076.The turn-on field and field enhancement factor of Ba:2%doped ZnO nanorods arrays are 2.68 V/?m and 6973.It is found that the field emission performance of Al:6%doped ZnO nanorods arrays is higher than the sample with doped Cu and Ba.(chapter 6).