Study Of Graphene Prepared By Chemical Vapor Deposition

Graphene, a two-dimensional crystal with monolayer atomic structure, have outstanding physical and chemical properties, such as excellent electrical conductivity, super large specific surface area, high transmittance of light, chemical stability and so on, which has made it have a broad application prospect in the field of electrode materials, nanometer electronics information storage, biological etc. many fields.In this research, we synthesize the high quality graphene on cooper foil based on low pressure chemical vapor deposition, and characterize the graphene by field emission scanning electronic microscopy and Raman spectrometer?Since there are many process parameters affecting the quality of graphene, we have mainly discussed the relation between the concentration of carbon source gas methane and hydrogen and the number of layer and the quality of graphene, with keeping growing time, annealing time, temperature and so on. The experiment result shows that when the ratio of methane and hydrogen flow rate is 0.05, the integrated intensity ratio of 2D peak to G peak (I2D/IG) is 2.75, and the integrated intensity ratio of D peak to G peak (ID/IG) is 0.41, which indicates the graphene synthesized on Cu (111) facet is monolayer and has few defects, and the ratio can be regard as the optimum parameter. On the other hand, we find that the two extreme cases, the high concentration of methane and the low concentration of hydrogen or the low concentration of methane and the high concentration of hydrogen, will both contribute to multilayer graphene. When the hydrogen partial pressure is high, the graphene edges tend to be terminated by hydrogen atom, which favors the diffusion of active carbon atom into the area beneath the initial graphene to form multilayer graphene as the inverted pyramid; When hydrogen partial pressure is low, the active carbon atoms have a chance to nucleate again on the nucleation of the initial graphene, which leads to multilayer graphene. At the same time, with the increase of methane concentration, the type of defect in graphene is transferred from edges defects into grain boundary defects. Hence, either methane or hydrogen has an important effect on the synthesis of graphene.In addition, we have briefly explored the quality of graphene grew on different crystal facet of copper foil. And the results express that the graphene synthesized on the copper(111) facet has less defects than the one on the copper(200) facet, and the copper(111) facet is easier to form carbon atoms cluster, which can affect the quality of graphene greater to the edges defects and grain boundary defects?...