The Synthesis Of Few-layered Graphene By CVD With Solid-state Carbon Source And In-situ Synchrotron Radiation X-ray Diffraction Studies

Graphene is a planar sheet from graphite,which is composed by a single layer of sp² hybridized C atoms arranged in honeycomb lattices.Since 2004,An-dre Geim and Konstantin Novoselov obtained graphene sheets isolated by the Scotch tape method,the extraordinary electronic,mechanical,thermal,chemical,and optical properties make graphene one of the most promising materials.It has rec eived particular attention in various technological applications,such as nanomech anical,biosensing and nanoelectronic devices.Up to now,there were several methods for preparation of graphene.Among them,chemical vapor deposition（CVD）is supposed to be one of the best methods for preparing large area and high quality graphene.However,the growth of large-area,uniform graphene with controllable thickness and compatible with back-end CMOS integrationare still not resolved.The main reason is that the microscopic growth mechanisms of graphene are poorly understood.In-situ observations have to be used to solve these problems,such as the microstructure evolution of surface and interface,the interaction of substrate and grapheme,carbon adsorption and segregation mechanisms.Synchrotron radiation light source with highbrightness,high intensity,low divergence and the ability to undertake in-situ experiments,is especially suitable for real-time growth dynamic study of graphene.Us-ing two-dimension synchrotron radiation X-ray diffraction method,the structure evolution of both graphene and substrate can be in-situ monitored with time resolution（several seconds）during the growth of graphene.Therefore,based on the above considerations,this thesis mainly cover the following sections:1)Set up an in-situ CVD research platformat beamline BL14B1 of Shang hai Synchrotron Radiation Facility.Various X-ray techniques can be performed f or the study of graphene growth process.The platform contains a CVD chamber with dual-zone heating,which can be worked at atmospheric pressure or low p ressure(1×10^-2Pa),the maximum temperature at sample is 1000℃.2)Basing on the in-situ CVD platform,we have obtained the high quality graphene on Ni and Cu using PMMA as solid carbon source.By adjusting tem-perature,heating rate,holding time,cooling rate,gas flow rate,the microstructure and morphology of graphene can be well controlled.3)The study on the growth mechanism of graphene by in-situ XRD with the platform in BL14B1 beamline of Shanghai Synchrotron Radiation Facility.By two-dimensional grazing incidence diffraction,we obtain the structure evoluti-on of graphene on the nickel substrate.We found that the formation of graph-ene can be divided into four stages:（1）carbonation of the solid carbon source;（2）the diffusion of carbon atoms into Ni lattice;（3）metal-catalyzed graphene nucleation at high temperature;（4）isothermal segregation of carbon atoms from Ni latti-ceto surface and the formation of graphene.Meanwhile,we found the slightly rotation of Ni grains during carbon diffusion process,which might be caused by t-he none quilibrium expansion of nickel lattice due to the carbon atom diffusio-n,indicting the strong interaction between Ni and graphene.4)The study on the growth mechanism of grapheme obtained by CVD with CH₄at different growth temperature with the platform,and show the significant impact on grapheme grows.