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Study On Optimization Of Graphene Transfer Process In Carbon-Based Devices

Posted on:2020-12-27Degree:MasterType:Thesis
Country:ChinaCandidate:J HuangFull Text:PDF
GTID:2381330623459784Subject:Optical engineering
Abstract/Summary:PDF Full Text Request
With the property of atomic thick layer,high mobility and thermal conductivity,graphene owns inherent advantages in electronic devices.Chemical vapor deposition?CVD?is the main method for the preparation of high-quality and large-area graphene films.The graphene films prepared by CVD have the characteristics of relatively large size and good film uniformity and continuity.However,the graphene prepared by the CVD method exists on the metal substrate,so it must be transferred to the target substrate by a suitable process to realize the application of graphene.The traditional wet transfer method may causes problems such as breakage,wrinkles and residual impurities on the surface of graphene.How to effectively transfer graphene which prepared by CVD method has become an urgent problem for researchers.In this paper,the CVD method and the transfer process of graphene were developed and optimized.The quality of graphene film was improved by the optimization of wet transfer process.Graphene field effect transistor?GFET?and graphene-silicon heterojunctions were made to verify the effect of process optimization on device performances.Finally,to combine the advantages of"ballistic transport"in the vacuum state nano-gap channel with the ultra-high mobility of graphene,a new type of graphene-based planar nano-gap channel transistor was made.The results show that better electrical performance can be achieved by this transistor.The main research contents and results of this paper are as follows:?1?The process optimization of the wet transfer process was systematically studied.The substrate was ultrasonically treated to increase the hydrophilicity and surface flatness,by this way,the wrinkles and cracks were reduced after evaporation of water molecules;the adsorption of water molecules,oxygen and polymer residues on the graphene surface are removed by thermal annealing and NaOH solution soaking;the results show that by using the optimized transfer process,the graphene prepared by CVD methods can be transferred to the target substrate with high quality;?2?The working mechanism of graphene field effect transistor?GFET?and graphene-silicon heterojunction photodetector were prepared and studied.The wet transfer optimization process was applied to the device fabrication process,and the results show that the carrier mobility of the GFET is nearly doubled after the ultrasonic treatment of the substrate combined with thermal annealing;after doping graphene by HNO3 vapor,the rectification characteristics and switching ratio of graphene-silicon heterojunction are improved,and the on/off current ratio has been improved by more than three times.?3?In order to solve the problem that the traditional GFET has low switching due to the inability to turn off the current,a new graphene-based planar vacuum nano-gap channel transistor is fabricated.The result shows that the transistor can switch from off-state to on-state and achieve an on/off current ratio of up to 102 with low operating voltage?<20V?and leakage current?<0.5nA?,which is two orders of magnitude higher than a back gate type GFET.
Keywords/Search Tags:Graphene, transfer process optimization, field effect transistor, heterojunction, vacuum nanogap
PDF Full Text Request
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