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Fabrication And Study On Functional Graphene And Tungsten Disulfide Field-effect Transistors

Posted on:2020-10-23Degree:MasterType:Thesis
Country:ChinaCandidate:R RongFull Text:PDF
GTID:2381330620951196Subject:Chemical Engineering and Technology
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Considerable interest has been recently given to the two-dimensional materials such as graphene and transition metal dichalcogenides?TMDCs?due to their unique electrical properties.Graphene exhibits ultrahigh carrier mobility,but the absence of a band gap seriously limits its application,controllable the bandgap of semimetal graphene is still need to be addressed to fully utilize this material.For TMDCs such as tungsten disulfide,in order to better apply them to field-effect transistor devices,p-n diodes and optoelectronic devices,it is particularly important to modulate the electrical properties by adjusting the charge transfer density of transition metal sulfides.In the current research work,a lot of effort has been devoted to exploring and improving their electrical performance.Doping is an effective method for regulating the electrical properties of two-dimensional materials,making them better applied to electronic devices.Methods for improving the performance of 2D materials by physical and chemical doping have been reported.However,it is still challenging to achieve reversible regulation of the electrical properties of 2D materials.In addition,the performance of 2D materials field effect transistor device is greatly affected by various factors such as material,environment and interface,to further enhance the applicability of 2D materials,modulating their electrical properties is essential.Therefore,based on previous research,this paper is devoted to modulate the electrical properties of 2D materials by doping,the doping effects were systematically evaluated by X-ray photoelectron spectroscopy?XPS?,atomic force microscopy?AFM?,Raman spectroscopy and electrical measurement results.The effects of the interface between the electrodes and the 2D materials were studied.The specific research contents are as follows.?1?Nitrogen-doped graphene was synthesized through a modified chemical vapor deposition?CVD?process.Combined with the Raman results,we demonstrate reversible regulation of N-doping graphene with sequential chemical treatment by adsorption and desorption of titanium?IV?bis?ammoniumlactato?dihydroxide?Ti complex?.The substitution doping nitrogen effectively affected the electrical structure of graphene and successfully became the absorbed centers of Ti complex.?2?Molybdenum disulfide and tungsten disulfide devices with different metal electrodes were obtained through physical construction methods.Comparison of electrical properties of the devices,the principle of metal-semiconductor contact surface energy band is analyzed to explain the reasons for the different conductivity of devices under different metal electrodes.Lower work function metals like indium has smaller schottky barrier heights at the metal-to-2D materials interface result in better carrier injection and hence better conductivity.Metals with higher work functions are more favorable for hole transport of 2D materials.?3?We explore how titanium?IV?bis?ammoniumlactato?dihydroxide can be used as a tunable and controllable surface dopant for WS2.After doping,the electrical properties of WS2 are changed from n-type conduction to p-type conduction.Combined with the XPS,Raman and AFM results,we have proved that titanium?IV?bis?ammoniumlactato?dihydroxide is a p-type dopant for tungsten disulfide.The effects of different metal electrodes on the electrical properties of the functionalized devices were investigated,it was once again proved that the metal electrodes with higher work functions are more conducive to the hole transport of the devices.
Keywords/Search Tags:Field-effect transistor, Transition metal dichalcogenides, Doping, Graphene
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