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Study On Fabrications And Thermoelectric Properties Of Graphene/Lithium Tantalate Field Effect Transistor

Posted on:2022-09-23Degree:MasterType:Thesis
Country:ChinaCandidate:Q X JinFull Text:PDF
GTID:2491306332493364Subject:Materials Science and Engineering
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As a two-dimensional single-layer material composed of carbon atoms that are closely packed,graphene has many excellent properties in light transmission,electricity,and mechanical behavior,which shows a subversive material in the future.With the advantages of adjustable atomic-scale thickness from single layer to several layers and the tunable band structure,graphene has highly sensitive to the dielectric field when it is combined with dielectric materials.Therefore,it can be used as a key sensing functional materials for sensing.In the graphene/pyroelectric material structure,the surface of the pyroelectric material can produce a high polarization electric field under the thermal effect,which can play a great role on the carrier transport performance of graphene.Therefore,this structure is suitable for exploring new pyroelectric sensors.In this thesis,graphene/lithium tantalate field effect transistors were prepared and studied by combining graphene with ultra-thin lithium tantalate.The specific research content is as follows:(1)The preparation process and electrical transmission characteristics of back-gate graphene field-effect transistors are studied.The substrate is treated with oxygen plasma,the hydrophilicity of the SiO2 substrate is improved,the wet transfer process of graphene is optimized,and a back-gate graphene transistor is prepared.The transfer characteristic curve is bipolar,the Dirac voltage is 5 V,the hole carrier mobility ?p=1863 cm2Ě(VĚs)-1,and the electron carrier mobility ?n=1371 cm2Ě(VĚs)-1.(2)The preparation process of graphene/lithium tantalate field-effect transistors is achieved on the basis of silicon-based back-gate graphene transistors.The influence of positive and negative photoresist lift-off process is explored on lithium tantalate crystals.The negative photoresist exposure process is used to optimize the lift-off process by using its inverted trapezoidal structure,developing an excellent ohmic contact between graphene and electrods.Finally atomic layer deposition(ALD)is developed to prepare Al2O3 achieving a graphene/lithium tantalate field effect transistor pyroelectric detector.(3)The performance of the prepared graphene/lithium tantalate field effect transistor is studied.Using ALD technique to grow Al2O3 isolation layer on graphene,the hole mobility of the graphene channel is increased from 754 cm2Ě(VĚs)-1 to 1630 cm2Ě(VĚs)-1,the Dirac voltage is moved 45 V to the left.Meanwhile,temperature response of the device is analyzed showing that the resistance reaches the maximum value of 7900 ? when the temperature rises to 61.2?,At the same time,temperature resistivity TCR is about 3.2%?-1 during 30?and 61.2?,while temperature resistivity TCR is about-3.94%?-1 during 61.2? and 66?.
Keywords/Search Tags:Graphene, Graphene Field Effect Transistor, Lift-off, Photolithography, Temperature Coefficient of Resistance
PDF Full Text Request
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