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The Modification Research Of Field Emission Properties Of ZnO And CuO Nanoarray Structures

Posted on:2018-07-11Degree:MasterType:Thesis
Country:ChinaCandidate:X F SuFull Text:PDF
GTID:2371330515995564Subject:Condensed matter physics
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The research on cold cathode emitters is still at the forefront of micro-nanotechnologies due to their field electron emission at room temperature without heating,can be highly integrated,no preheating delay,high emission current density at low electric fields and at room temperature along with high emission stability and repeatability.According to the Fowler–Nordheim?F–N?theory,the field emission of a material is dependent on its work function and field enhancement factor.The lower the work function of the material,the field emission efficiency is higher.Secondly,the field-enhancement factor,which is the ratio of the local field to the applied field,depends solely on the shape and morphology of an emitter.In recent years,it is understood that the preparation of low-function,adjustable geometric shape and stable performance of metal oxide nanostructured materials and its field emission modification research will become an important topic in the application of nanomaterials physics and devices.The structure of ZnO and CuO nanometer structure arrays have the advantages of low work function,strong oxidation resistance,high temperature resistance,stable structure of morphology and simple preparation process,they are the potential candidate materials for field electron emitters.However,it is necessary to further reduce the turn-on field?or threshold field?of the emitter and increase its emission current density.Based on the review and analysis of the existing work,this dissertation puts forward new ideas and new ways to solve the above problems,and as the subject of"The modification research of field emission properties of ZnO and CuO nanoarray structures"to systematically summarize research works of the author during the period of study for a master's degree.Mainly related to the following two aspects of the research content and results:1.First,vertical and uniform zinc oxide?ZnO?nanorod arrays?NRAs?with sharp tips were fabricated on Zn substrate by a straightforward hydrothermal method without the assistance of the seed layer,template or surfactant.Whereafter the as-synthesized ZnO NRAs were successfully doped by oxygen vacancy in sodium borohydride?NaBH4?solution,aiming to generate a donor energy level below the conduction band.The liquid reduction method compared with other methods,the experimental equipment requirements are low,the process is simple and the security is high.More importantly,the concentration of doped oxygen vacancy can be effectively controlled by adjusting the temperature of the reduction process,and ultimately achieve the purpose of controllable tailoring the band structure of ZnO NRAs.When the liquid phase reduction temperature is 90°C,the doped ZnO NRAs present a lower turn-on field of 0.67 V/?m,higher field enhancement factor of 64601and good field emission stability.2.The uniform and vertical CuO nanosheets were prepared on the Cu foil by a simple and low temperature solvothermal method.Then,the CuO nanosheets were covered with GO by spin coating,and a large number of GO sharp protrusions were formed on the GO film surface.Due to the presence of GO,this composite structure has better electrical conductivity compared to pure CuO nanosheets.A host of effective field emission sites greatly improve the field emission performance of GO/CuO composite structures.The composite structures have a lower turn-on field of 1.7V/?m,a larger field enhancement factor of 2880.Its repeatability and long-term stability are also better.
Keywords/Search Tags:field electron emission, ZnO nanorods arrays, oxygen vacancy doping, CuO nanosheets, graphene oxide
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