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Synthesis, Characterization And Performance Research Of Graphene

Posted on:2015-01-24Degree:DoctorType:Dissertation
Country:ChinaCandidate:B HeFull Text:PDF
GTID:1221330467971182Subject:Chemistry
Abstract/Summary:PDF Full Text Request
Graphene is a novel material which attracts people’s attention currently. It has many notable properties including bipolar electrical characteristic, high carrier mobility, quantum hall effect in room temperature, controllable band gap, high transmittance, excellent mechanical and thermal properties, efficient hydrogen storage, peculiar magnetism and perfect interaction in charge. Due to its excellent peoperties, graphene is considered to be the next generation materials applied in microelectronic device, organic optoelectronic material, high efficiency hydrogen storage material, muti-functional composites and biomedical material. In order to achieve the application of graphene in relative area, it is important to research the preparation method of massive graphene with low cost. Meanwhile, the research on controllable preparation of graphene with large area and high quality is significant. Moreover, modification is an effective method to expand the application of graphene. In this paper, our works were mainly devided into three aspects as follows:1. Research on graphene preparation with oxidation-reduction method including thermal reduction and electrochemical reduction. In the research of thermal reduction method, modified Hummers method was employed to synthesis graphene oxide dispersing in water. Atomic force microscope was used to observe the surface topography and structure of monolayer and few layer graphene. Raman spectroscope and X-ray photoelectron spectroscope were used to detect the structure of reduced graphene after different thermal treatment conditions. It can be proved that increasing temperature is beneficial to restore the defect in graphene and promote the reduction. Organic ribbon mask method was employed to fabricate back-gate field-effect transistor based on the reduced graphene. The results indicated that the obtained graphene exhibited p-type electrical characteristic in air condition, which enhanced with the rising of temperature. The maximum hole mobility was6.2m2·V-1·s-1which was higher than that of devices based on the graphene reduced by hydrazine hydrate in solution. This research provided us a reliable proof of preparing graphene with thermal reduction of graphene oxide. In the research of electrochemical reduction method, scanning electron microscope was used to ensure the optimal reaction time and temperature of graphene growing on copper surface. Optical microscope, atomic force microscope and transmission electron microscope were employed to analysis the surface and internal structure of reduced graphene. Scanning electron microscope, Raman spectroscope, X-ray photoelectron spectroscope and X-ray diffracmeter were used to demonstrate the effect of temperature on the structure of graphene, therefore optimized the structure quality and electrical properties of graphene. The obtained graphene membrane exhibited high conductivity which was meaningful to the fabrication of large area conductive film based on graphene.2. Research on controllable synthesis of large area graphene with high quality. Polyethylene, Polystyrene and Polyethylene oxide were chosen to grow graphene films. Raman spectroscope and scanning electron microscope were used to analysis the impact on the quality of graphene by the structure of the polymer precursor, which broadened precursor domain of graphene. After that, large area graphene with fine lattice structure and different thickness was synthesized from high-oriented polyethylene. Optical microscope, atomic force microscope and scanning electron microscope were employed to characterize the surface morphology of graphene. The results of Raman spectroscopy and transmission electron microscopy indicated that the lattice structure of graphene derived from high-oriented polyethylene was better than that derived from disoriented polyethylene. The adjacent layers of graphene were well-ordered stacking which was uninfluenced by the number of layers. The test results of transmittance and resistance under various temperature indicated that the graphene membrane derived from high-oriented polyethylene possessed well optical and electrical properties which achieved the criterion of transprent electrode materials, and this method provided us an important way to grow high quality graphene controllably.3. Research on synthesis of large area of nitrogen-doped graphene. Large area of nitrogen-doped graphene with single-layer was obtained successfully from poly4-vinyl pyridine. Raman spectroscope and X-ray photoelectron spectroscope were used to ensure the optimal conditions for growing products, under which the nitrogen content was6.37%. The results of scanning electron microscopy, atomic force microscopy, Raman spectroscopy and transmission electron microscopy indicated that the graphene had a well surface topography and monolayer structure. The devices based on the obtained nitrogen-doped graphene exhibited excellent n-type electrical properties under air or under high vacuum conditions. The electron mobilities of the devices reached364.68m2·V’1·s-1under vacuum with high transmittance and still had a value of229.36m2·V-1·s-1in air after thermal treatment with the elevation of transmittance. The nitrogen-doped graphene we produced afforded a new method and the corresponding precursor to dope graphene.
Keywords/Search Tags:graphene oxide, copper foil, high-oriented polyethylene, nitrogen-doped graphene, field-effect transistor
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