Study On Preparation Of High Quality Graphene By Microwave Plasma Chemical Vapor Deposition

Graphene, a sp² hybridized carbon sheet with a honeycomb structure, has numerous physical and structural properties because of its unique single atomic layer of carbon atoms in a hexagonal lattice structure. Microwave Plasma Chemical Vapor Deposition?MPCVD? is superior to the others from the advantage to achieve deposition at low reaction temperature? short time and different substrate by use of reactive species generated in the plasma. But it still exist some problems for large-scale deposition of graphene using MPCVD, such as the uniformity of graphene and the difficulty to control layer number. Aiming at above-mentioned practical problems, we need to go on seeking more excellent graphene deposition parameters. In this research,graphene film synthesis was carried out in a self-made 10 kW stainless steel ring-cavity MPCVD system with methane as the main source of carbon, hydrogen and argon gas as auxiliary gas and Cu? Ni and Si as substrates. And the samples were characterized by optical microscopy, Raman spectroscopy?Raman?, scanning electron microscope?SEM?, transmission electron microscopy?TEM? and energy dispersive spectrum?EDS? in order to analyze the influences of different process parameters on the deposition quality of graphene and the corresponding mechanism to obtain graphene synthesis technology of high quality and controllable layer number. The main researches are as follows:1 ? Systematically study the influence of different annealing time on surface morphology and crystal orientation of copper foil in 100 sccm H2 and 100 sccm Ar atmosphere. And X-ray diffraction?XRD? and scanning electron microscope?SEM?results show that the consistent orientation of copper foil,smooth and clean surface and larger grain size after 30 min annealing.2?The influences of process parameters of temperature, pressure, power, growth time and air ratio on the graphene microscopic structure?layer and defect density?were studied using Raman spectroscopy. Then combined with transmission electron microscopy?TEM?, scanning electron microscopy?SEM?, energy dispersive X-ray spectrum?EDS? and optical microscope results analysis: 5.5 kW, 7.4 kPa and 650 ?are the optimum microwave power, deposition pressure and the growth temperature,respectively. We can adjust deposition time to obtain uniform and controlled layer number graphene under above deposition conditions.3 ? It is found that the numbers of layers, defects and surface morphology of as-obtained graphene films depend strongly on the duration time of in-situ hydrogen plasma. And hydrogen plasma in the post-treatment process play two roles: At the early stage, the residual carbon species could be used to further growth of graphene films in the hydrogen plasma environment; Subsequently, the main role of in-situ hydrogen plasma was to the gradual etching of the topmost layer.4 ?The influence of different annealing atmosphere on nickel foil morphology using MPCVD were researched in order to obtain smooth and clean, larger grain size of nickel foil. Then carbon source was introduced into the chamber to grow the nonuniform layer number graphene films on Ni foil.5?Diamond film growth use graphene as transition layer on Cu substrate. And graphene quality plays a crucial role on diamond nucleation density.6?The different forms of carbon material were deposited on single crystal-silicon substrate by adjusting carbon source concentration and growth temperature. Scanning electron microscopy?SEM? and Raman spectroscopy results show that similar CNW structure were obtained under 850 ? growth temperature, the atmosphere of 100 sccm CH₄ and200 sccm H₂.