| Graphene,a new type of two-dimensional nanomaterial,is composed of single-atom thick sheet carbon atoms,densely arranged into a honeycomb crystal structure.Graphene has excellent carrier mobility and high aspect ratio,making it one of the best choice for field emission materials.Graphene is a good field emission material.Although chemical vapor deposition?CVD?is used to prepare graphene cathode,it can form prominent and sharp edges,but most of them are also smooth.The good chemical stability of zinc oxide and the formation of different crystal structures can make zinc oxide a good choice for field emission materials.Considering the combination of graphene and zinc oxide will better improve the performance of cathodic field emission,the field emission properties of graphene/zinc oxide composite cathodes are studied.The main contents of this paper are as follows:First,the large area single layer graphene thin films were prepared by CVD method.The field emission properties of graphene cathodes were studied,and the effect of deposition parameters on the field emission properties was also discussed.The results show that the quality of the graphene film is better when the growth temperature is1030?,and it has a higher emission current density.The growth time of 5 min graphene films have better field emission properties,field enhancement factor can reach 1316.6,the reason is that with the growth time of the graphene surface area will be expanded and clustered into flat sheet,and the shortest time of 5 min due to not formed graphene sheet continuous,will produce a bulge and tip,lead to better performance emission.Then we transfer graphene to indium tin oxide?ITO?,prepare graphene/PEDOT:PSS modified organic light-emitting diodes?OLED?,and PEDOT:PSS as hole modification layer OLED devices.Then the graphene/zinc oxide composite films were synthesized by sol-gel and hydrothermal method on the basis of CVD and wet method.By changing the concentration of reactants,reaction time and reaction temperature to synthesize the composite films with different morphologies.The results indicate that the reaction concentration of 10 mM,the reaction time is 4 h and the reaction temperature is 95degrees centigrade making better field emission properties.Turn-on field of 3.25 V/m has a higher current density,which can reach 1.5 mA/cm2.The field enhancement factor can maximally up to 4735.02 and the field emission current density and the field enhancement factor have been greatly improved compared with the pure graphene cathode.Finally,by changing the different substrates?the zinc oxide nanorods were grown on the copper foil substrate and on the ITO?and comparing the morphology of the films on different substrates,it further shows that the combination of graphene with zinc oxide in SiO2/Si substrate is better and is more conducive to the study on the field emission cathode.Based on the analysis above,this paper first uses CVD to prepare graphene films and studies the field emission properties of pure graphene,then adopts wet transfer method for transferring grapheme to SiO2/Si,with the combination of spin coating ZnO seed solution and hydrothermal method to synthesize the zinc oxide nanorods to prepare graphene/zinc oxide composite films.At last,the paper studies the field emission properties of composite cathode. |
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