Fullerene Transformed into a 3‑D Structure of Nitrogen-Doped Few-Layer Graphene Sheets: Growth and Field Emission Properties

Abstract

3-D-structured nitrogen-doped few-layer graphene sheets (3-D NFLGs) have been prepared using a fullerene C60 precursor combined with a microwave excited nitrogen plasma process. A deep understanding of the growth mechanism and regulating of morphology that can adjust the field emission properties is crucial for its widespread application. In this work, the detailed growth process and microstructure and the field emission properties of the as-synthesized vertical aligned 3-D NFLGs were studied. The growth of the 3-D NFLGs can be divided into three steps: evaporation of the C60, opening of the C60, and formation of the 3-D NFLGs. The growth process and morphology of the materials can be neatly regulated by changing the evaporating temperature of the C60, electron temperature of the plasma, and substrate temperature through our self-designed reaction equipment. Interestingly, the vertical 3-D NFLGs grew at a limited microwave power and nitrogen pressure and could be divided into three different morphological features, reflected in their distribution uniformity, interparietal distance, number of layers, and crystallinity, which exhibited different field emission properties. Additionally, the 3-D NFLGs were all in situ doped with ∼4% nitrogen atoms from nitrogen gas during the growth process, while different compositions of the nitrogen atoms were reflected in the graphitic N increasing with increasing nitrogen pressure. Furthermore, the field emission measurements show that the as-obtained vertical 3-D NFLGs exhibited the lowest turn-on electric field (1.30 V/μm@10 μA/cm2) and threshold field (2.1 V/μm@1 mA/cm2) at the M1 morphology and the highest stability at the M3 morphology. Remarkable field emission performance was obtained for the 3-D NFLGs with M2 morphology, showing their great potential for field emission applications