研究目的
To investigate the low-damage nitrogen incorporation in graphene films by nitrogen plasma treatment and the effect of airborne contaminants.
研究成果
The late afterglow of microwave N2 plasma enables high nitrogen incorporation (up to 29.4% N/C) in graphene with low damage (D:G ratio 0.35-0.45). However, most nitrogen is weakly bonded and lost after transfer to SiO2/Si, indicating that aromatic inclusions are minor. The method is effective for low-damage functionalization but requires careful interpretation of nitrogen signals due to contaminants.
研究不足
The study is limited by the presence of airborne contaminants that affect nitrogen incorporation, and the transfer process may remove weakly bonded species. Oxygen contamination and sample inhomogeneity due to polycrystalline substrate could influence results. The exact nature of nitrogen moieties remains undetermined.
1：Experimental Design and Method Selection:
Graphene films grown by CVD on copper foil were treated in the late afterglow of a microwave N2 plasma at reduced pressure (6 Torr) with a gas flow rate of 100 sccm. The setup included a surfatron wave launcher for plasma generation. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy (RS) were used to analyze nitrogen incorporation and defect density.
2：Sample Selection and Data Sources:
CVD-grown graphene on 25 μm copper foil (Alfa Aesar item No. 13382) was used. Samples were stored in atmospheric conditions for a month before treatment to ensure reproducibility.
3：List of Experimental Equipment and Materials:
Equipment includes a microwave plasma system with surfatron, XPS device (ESCALAB 3 MKII with Al Kα and Mg Kα sources), Raman spectrometer with 488 nm and 514 nm lasers, SEM for spot size verification, and materials like ultra-high-purity N2 gas, gas purifier (SAES Pure Gas Inc Nitrogen MC1-920F), and chemicals for transfer (PMMA, ammonium persulfate, acetone, isopropanol).
4：Experimental Procedures and Operational Workflow:
Samples underwent five 30-second plasma treatments (total 150 seconds). After each treatment, XPS and RS measurements were performed. For RS, measurements were taken at specific locations on graphene on copper and copper oxide. After final treatment, samples were transferred to SiO2/Si substrates using PMMA and etching, followed by additional XPS and RS.
5：Data Analysis Methods:
XPS data were analyzed using peak fitting with sensitivity factors. RS data were analyzed by deconvoluting spectra to determine D:G ratios, with corrections for laser wavelength differences.
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