Large-area synthesis of carbon nanofibres at room temperature

Abstract

Carbon nanotubes, first identified by Iijima¹, require for their production a source of elemental carbon and a transfer of energy that is specific to the type of source and the growth environment. Methods developed so far involve arc discharge², and vaporization using laser^3,4, pyrolysis^5,6 and chemical vapour deposition of hydrocarbons⁷. Here, we show growth of carbon nanofibres from radio-frequency plasma-enhanced chemical vapour deposition at room temperature, which was made possible by substituting the thermal energy requirements for the growth with plasma decomposition of methane on the Ni catalyst. Electron microscopy analysis provides evidence for a 'tip' growth model⁸, with the Ni catalyst particle attached to the tip of the nanofibre. Energy-filtered imaging shows the Ni catalyst has a surface layer rich in carbon, consistent with the formation of a eutectic Ni–C droplet as a nucleation site for the carbon nanofibres⁹, so that the carbon diffuses across the surface. The reduced distortion of the catalyst particles at low temperatures leads to a more uniform growth of the carbon nanofibres over large areas. The lower growth temperature allows for the removal of the silicon dioxide barrier layer associated with catalytic growth, and should allow in situ growth of nanofibres on relatively large areas of temperature-sensitive substrates, such as plastics, organics and even paper.