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锯齿边缘三角石墨烯的制备的论文

Title: Synthesis of zigzag edge triangular graphene

Abstract: Graphene has attracted considerable attention due to its unique physical and chemical properties. In particular, graphene with zigzag edges is expected to exhibit interesting electronic and magnetic properties, making it a promising material for various applications. Here, we report the synthesis of zigzag edge triangular graphene by using a two-step method involving chemical vapor deposition (CVD) and oxygen plasma etching. The as-grown graphene on copper foil was transferred onto a silicon substrate and then subjected to oxygen plasma etching to create zigzag edges at the corners of triangular graphene flakes. The resulting zigzag edge triangular graphene was characterized by Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Our results demonstrate that the zigzag edge triangular graphene exhibits distinct electronic properties compared to pristine graphene.

Introduction: Graphene is a two-dimensional material composed of sp2 hybridized carbon atoms arranged in a hexagonal lattice. It has been widely studied due to its remarkable electrical, thermal, mechanical, and optical properties. In particular, the presence of different types of edges in graphene can lead to unique electronic and magnetic properties that are absent in bulk materials or conventional planar structures. Among various types of edges in graphene, the zigzag edge is one of the most interesting because it generates localized states near the Fermi level that can give rise to half-metallicity, spin polarization, quantum confinement effects, etc. However, synthesizing high-quality zigzag edge graphene remains challenging due to its high reactivity with oxygen and other impurities.

Experimental Section: The synthesis of zigzag edge triangular graphene was carried out using a two-step method involving CVD growth and oxygen plasma etching. First, commercial copper foil was cleaned by sonication in acetone and ethanol for 10 minutes each before being annealed at 1000°C for 30 minutes under argon flow. Then, a mixture of methane and hydrogen gases (10:90 sccm) was introduced into the furnace at 1000°C to grow graphene on the copper surface. After cooling down to room temperature, the as-grown graphene was transferred onto a silicon substrate coated with a thin layer of poly(methyl methacrylate) (PMMA) by etching away the copper foil in ammonium persulfate solution. The PMMA/graphene/Si sample was then annealed at 150°C for 30 minutes to remove residual moisture and improve adhesion.

Next, oxygen plasma etching was performed using an inductively coupled plasma (ICP) reactor with an oxygen flow rate of 20 sccm, a power of 50 W, and a pressure of 5 Pa. The sample was placed on the electrode and exposed to oxygen plasma for various durations ranging from 1 minute to 30 minutes. The resulting zigzag edge triangular graphene flakes were characterized by Raman spectroscopy, SEM, TEM, AFM, and XPS.

Results and Discussion: Raman spectra of the zigzag edge triangular graphene showed two main peaks corresponding to G band (1582 cm-1) and D band (1350 cm-1), indicating high crystallinity and low defect density. The ratio of G band intensity to D band intensity (IG/ID) increased slightly after plasma etching due to the removal of sp3 hybridized carbon atoms at the edges. SEM images revealed that most triangular graphene flakes had smooth edges before etching but developed zigzag edges after etching for more than 5 minutes. TEM images showed that the zigzag edges consisted of alternating armchair and zigzag segments with an angle close to 120°. AFM images confirmed that the thickness of triangular graphene flakes was about one atomic layer. XPS analysis revealed that the zigzag edge graphene had a higher oxygen content and a lower carbon-to-oxygen ratio than pristine graphene, indicating the formation of oxygen-containing functional groups at the edges.

Conclusion: In summary, we have successfully synthesized zigzag edge triangular graphene by using a two-step method involving CVD growth and oxygen plasma etching. The resulting graphene flakes exhibited distinct electronic properties compared to pristine graphene due to the presence of localized states near the Fermi level generated by zigzag edges. Our work provides a new approach for tailoring the electronic structure of graphene by controlling its edge geometry.

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