| Graphene, an important two-dimensional carbon structure with a one-atom-thick planar sheet, has drawn much attention in many research areas because of its exceptional properties, including high intrinsic carrier mobility, superior mechanical strength, high thermal conductivity and high optical transparency. The growth of high-quality large-area monolayer and multilayer graphene is of fundamental importance for developing its applications in nano-electronic devices, biomedicine, solar cells, supercapacitors and thin solid lubricant. However, the simple exfoliation of graphene from graphite reported in the initial research is limited to micrometer sizes and low yield. Reduced graphene oxide sheets made by self-assembly could provide a low-cost alternative with high throughout, but the as-made graphene films exhibit poor electrical properties. In contrast, large-size and high-quality graphene can be grown epitaxially on silicon carbide. However, silicon carbide wafers are relatively expensive. Moreover, the growth is performed at a high temperature(?1500°C) under ultrahigh vacuum, increasing the energy cost of the growth process. Recently, graphene growth on transition mental surface, including Ni, Cu, Ru and Pt, has been developed to fulfill the requirement by chemical vapor deposition(CVD). Among these metallic catalysts, Ni and Cu are preferred because of their accessible and easy control. The Cu-assisted CVD method, involving a surface catalytic process due to the low solubility of carbon in Cu, leads to graphene film growth almost exclusively as a single layer. In the case of Ni, because of its high carbon solubility at high temperatures, the carbon atoms diffuse and precipitate in the Ni matrix, leading to a segregation mechanism by which both monolayer and multilayer graphene can be synthesized depending on the experimental conditions.However, with limited understanding of the detailed growth mechanism(s) and the in-situ process, growth control remains rudimentary and the graphene growth on Ni cannot be well controlled. CVD optimization has in most cases focused empirically on the carbon dose and the process temperature profile. Due to its high brightness, tunable energy, coherence, large equipment integrated space and so on, synchrotron radiation facility can provide many advantages in nanomaterial characterization. Compared to conventional characterization techniques, techniques based on synchrotron can offer unique opportunities to study materials and obtain the in-situ and real-time information. Thus, based on the BL14B1 beamline of Shanghai Synchrotron Radiation Facility(SSRF), we develop a in-situ facility for rising samples temperature from room temperature to 1400?, which can realized the real time x-ray diffraction characterization on heating up, annealing and cooling process. What is more, a in-situ CVD facility is setting up for real-time study graphene growth equipped in BL14B1 beamline.Based on sub-second time resolution detection technique in BL14B1 beamline and the in-situ CVD facility build up by ourselves, In-situ two-dimensional grazing incidence X-ray diffraction was applied in isothermal growth of graphene on nickel through chemical vapor deposition. The analyses showed that the graphene interlayer spacing decreases with the increasing number of graphene layers(growth time increase). Moreover, the as-deposited graphene can be gradually removed through in-situ Ar annealing treatment and inverse interlayer spacing change was also observed, i.e., the interlayer spacing of graphene increases with the number of graphene layers decrease. These results prove that there is a strong coupling effect between the interlayer spacing and the number of graphene layers. The weak interlayer interactions between graphene layers and the lattice strain from the substrate may contribute to this phenomenon. |
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