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Study On Graphene Field-Effect Transistor And Graphene/Tungsten Disulfide Gas-sensing Characteristics

Posted on:2022-02-07Degree:MasterType:Thesis
Country:ChinaCandidate:Z X LiFull Text:PDF
GTID:2481306506961739Subject:Mechanical engineering
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Graphene and related two-dimensional materials offer prospects of unprecedented advances in device performance at the atomic limit,and a synergistic combination of graphene with silicon chips promises a heterogeneous platform to deliver massively enhanced potential based on silicon technology.In this work,mechanically exfoliated monolayer graphene was transferred to the patterned substrate to fabricate the GFET.We studied the electrical performance of GFET under different structural substrates.The electrical characteristics of the device after breakdown were also discussed.In addition,a graphene/WS2 gas sensor was constructed as well as the adsorption mechanism of the material was revealed,and hence the detection of NH3 by the device was realized.Two different GFETs have been fabricated by micro-nano processing technology.After the electrical performance of GFETs was measured,we found that the output curves of the two GFETs passed through the origin of the coordinate and hence reflected a superior linear relationship.Compared with suspended GFET,thin-gate GFET is easier to realize electrical regulation under small voltages.The gate voltage range of the thin-gate GFET is only-4-4 V.Owing to charge pinning effect and test environment,the electron-hole asymmetry of the transfer curve of the thin-gate GFET is obvious,leading to the charge-neutral point to shift positively.The scattering of impurities on the surface of graphene and substrate is the main reason for the low carrier mobility.At room temperature,the carrier mobility of the suspended GFET and thin-gate GFET is about 3043.8 cm2 V-1 s-1 and 539.8 cm2 V-1 s-1,respectively.Under the high electric field,SiO2 is broken down to form point defects.Point defects will increase immensely and contact one another,forming conductive channels that penetrate the oxide layer eventually.The graphene directly contacts with Si and forms Schottky contacts.The device is a Schottky-like diode after breakdown.The electrical properties of the device after breakdown have changed.The output characteristic curve is shifted along the ordinate,and the transfer characteristic curve appears unipolar.This research can provide a basis for judging channel material contamination or device failure.The gas sensor was fabricated with graphene/WS2 composite material,and the device can detect NH3 at 30C and 60C.The increase of temperature accelerates the movement of gas molecules,resulting in a shortening desorption time of NH3.Most NH3 stayed on the graphene/WS2 by physical adsorbed.In addition,high temperature can improve the contact between the part of the graphene and electrodes,as well as reduce the overall resistance of the device.At 30C and 60?,the responsiveness of the gas sensor to 100 ppm NH3 is 2.42%and 1.73%,respectively.The results are consistent with the prediction that the graphene/WS2composite material can achieve the detection of NH3.This research offers us more freedom in the construction of graphene gas sensors and their applications.
Keywords/Search Tags:graphene, field-effect transistor, electrical breakdown, Schottky-like diode, gas sensor
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