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Research On Graphene-based FETs And Heterojunction Devices

Posted on:2021-04-23Degree:MasterType:Thesis
Country:ChinaCandidate:Z Y XingFull Text:PDF
GTID:2381330623968387Subject:Engineering
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In the past ten years,two-dimensional materials have attracted widespread attention as the most promising electronic materials in the post-silicon era.Among them,graphene has ultra-high carrier mobility,which makes it stand out from many two-dimensional materials to replace traditional silicon in future integrated circuits.In addition,graphene can be prepared over a large area by chemical vapor deposition,which is another great advantage.However,because graphene grows on the surface of copper foil and cannot be directly grown on the target substrate,it needs further transfer to be applied,and the transfer process can easily cause unnecessary doping,destruction and pollution of graphene.Focus on solving one of the problems.In addition,the surface of graphene exposed to the external environment easily adsorbs molecules such as water and oxygen in the air,causing doping,and easily affecting the characteristics of the graphene transistor.Besides,graphene itself lacks a band gap,which results in the extremely low switching ratio of traditional graphene field effect transistors,which severely limits its practical application potential,especially for logic circuits.In view of the above problems,we first explored the growth of graphene.After research,we found that the surface oxide of copper and the growth airflow ratio have an effect on the growth of graphene.The copper surface was treated with APS for 30s to remove copper oxides,and the airflow ratio was Ar:H2:CH4=50:90:30.A continuous and complete single-layer graphene film could be grown.Provide support for subsequent device exploration.Then,in view of the common impurities,damage,and wrinkles of graphene transfer,this article explores from three aspects:target substrate,graphene/Cu,and corrosive fluid.It was found that improving the hydrophilicity of the substrate by isopropanol can significantly reduce the damage and wrinkles during the transfer,and avoid damage to the substrate.Acid-base transfer can remove Fe ions and various metals and metal oxide particles on the graphene surface,and the transfer effect It is even better than APS transfer.At the same time,RIE is also performed to remove the back graphene and high temperature annealing to decompose PMMA impurities and many other improvements.The Hall test has a low sheet resistance of 856?/?9?and a high carrier mobility of 1349 cm2/?VĚs?.Subsequently,research on graphite-related devices was conducted,and it was found that RIE patterned graphene at low power of 20 W can avoid photoresist residues.IGZO is more effective in isolating the device from air than PEI passivation layer,because IGZO grown under high vacuum does not affect graphene Causing contamination.Subsequently comparing GFETs prepared with different transfer methods,it was confirmed that the acid-base-assisted transfer GFET Dirac point was very close to the intrinsic graphene Dirac point at 1.98 V,and the carrier mobility was1305.01 cm2/?VĚs?.IGZO/graphene heterojunction field effect transistor is prepared.IGZO not only serves as a passivation layer but also acts as a conductive channel.The final device switching ratio can reach 7.81Î104.
Keywords/Search Tags:graphene, acid-base assisted transfer, graphene transistor, heterojunction, ON/OFF current ratio
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