Graphene Structure Tuning Based On Copper Substrate By Chemical Vapor Deposition

The basis for the application of graphene with excellent properties lies in its controllable preparation.Although the preparation technology of graphene has been greatly developed within more than ten years,the precise control of graphene structure,such as folds,grain boundaries and adlayers,is still insufficient.In order to address these problems,this dissertation paid great attention to the graphene film by chemical vapor deposition(CVD)based on Cu substrate,taking the "research method-material evaluation-preparation technology" research route to regulate the graphene folds,grain boundaries and adlayers.The main contents are as follows:(1)To address the problems of low efficiency of batch experiments and the influence of experimental results by system fluctuations,a dynamic research method for the kinetic process of material growth was proposed.The method can present the material growth process or investigate multiple parameters in one experiment by the relatively moving between the sample and reaction space,according to the reaction conditions in space and time.The kinetic evolution process of graphene nucleation and growth was investigated by using this method,which had proved the practicality of the method.(2)According to the features of graphene/copper surface morphology,graphen films before and after transfer of the same postion were characterized,using optical microscope,scanning electron microscope(SEM),atomic force microscope,and Raman spectroscopy,The Cu substrate below the folds was prone to oxidation,which changed SEM image contrast as the pseudo-multilayered graphene.The conventional transfer method did not introduce new wrinkles,but Cu steps that were too high instead introduced.Weakening the Cu evaporation could to some extent reduce the introduction of wrinkles.The correlation between fold morphology and structure was investigated,and the quality of graphene films was further improved by fold-etching and regrowth.(3)Graphene single crystals prepared by multi-core nucleation method is limited to Cu(111),with poor reproducibility and unclear influence mechanism.To solve this problem,the effects of temperature and atmosphere on the orientation of graphene domains on nucleation were systematically investigated.The carbon impurities in the Cu substrate were the main reason for destroying the orientation of graphene domains,and using high-purity Cu foils or pre-oxidizing Cu foils can also help this The appropriate growth temperature was another key factor,while the growth atmosphere had little effect on the orientation of graphene domains.Graphene domains can also be achieved on the high-index Cu facets.The asymmetry of high-index facets provided nucleation sites for graphene and enhanced the limitation of the optimal growth orientation angle.The graphene films prepared on high index Cu facets showed great electrochemical corrosion resistance,thermal oxidation resistance and electrical property.(4)Growth mechanism,regulation,and application of multilayer graphene.Combining isotope labeling and the co-localized characterization method,the growth of multilayered graphene with various morphologies was proved to follow the underneath mechanism and a multi-core cake model was put forward.The morphology of adlayers was controlled by the lateral diffusion of carbon to the graphene/Cu interface,which was further tuned by atmosphere and temperature.Besides,monolayer-multilayer hybrid graphene film was synthesized,which possessed the good mechanical properties of the multilayer and retains the transparency of the monolayer to the electron beam.The hybrid film was self-suspended transferred as a support film for transmission electron microscopy grid for the observation of nanoparticle microstructure.These research results of this dissertation was meaningful to the development of controllable preparation technology of graphen.