1 / 2015-10-21 00:48:40

CVD Synthesis of Carbon Nanostructures on Copper Surface.

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Carbon nanostructures such as graphene, carbon nanofibers, and nanotubes recently are distinguished as a promising components for new generation electronic and optoelectronic materials. The systematic study of the nanocarbons growth on the copper surface of different roughness by CVD process shows that graphene layers or nanofibers (CNFs) forest maybe synthesized at the variation of gas phase carbon-contained species, reaction pressure and temperature.
Graphene monolayers were synthesized in methane/hydrogen atmosphere. It is shown that the given parameters of synthesis a continuous layer of graphene does not form at pressures less than 2.4 mbar. At the pressure 2.4 mbar uniform coating of the substrate one or two-layer high-quality graphene is observed, it is confirmed by micro-Raman and XPS studies. Pressure growth to 5 - 10 mbar increases the thickness of the synthesized graphene layers. At pressures of 5-10 mbar the D mode is observed in Raman spectra, indicating the presence of structural defects. Using the method of photoelectron spectroscopy showed that an increase in pressure from 2.4 to 10 mbar, the number of layers increases from 1 - 2 to 4. At atmospheric pressure, the synthesized product represents 7 - 8 graphene layers without stress, tightly covering the copper substrate.
The increase of surface roughness leads to separate CNF and then CNFs “forest” appearance. It was shown that the structure of CNFs are strongly depends on temperature and C:H ratio in the gas phase; at the higher carbon concentration there are thicker fibers with the structure of “pile of coins” type, whereas with the decrease of carbon concentration the thickness decreased and fiber showed exact “bamboo”-like structure. Finally the model of nanocarbons formation and growth had been suggested.
Work was supported by the Ministry of Education and Science of the Russian Federation (Project doi: RFMEFI58114X0006)