Growth of multiwall carbon nanotubes in an inductively coupled plasma reactor

A high density plasma from a methane-hydrogen mixture is generated in an inductively coupled plasma reactor, and multiwalled carbon nanotubes (MWNTs) are grown on silicon substrates with multilayered Al/Fe catalysts. The nanotubes are vertically aligned, and the alignment is better than the orientation commonly seen in thermally grown samples. A detailed parametric study varying inductive power, pressure, temperature, gas composition, catalyst thickness, and power to the substrate is undertaken. Transmission electron microscopy and Raman spectroscopy are used to characterize the nanotubes. Emission spectroscopy and a global model are used to characterize the plasma. The power in the lower electrode holding the substrate influences the morphology and results in a transition from MWNTs to nanofibers as the power is increased. (C) 2002 American Institute of Physics.