Growth of carbon nanotubes by microwave plasma-enhanced chemical vapor deposition at low temperature

Carbon nanotubes have been grown on Ni-coated Si substrates by microwave pl asma-enhanced chemical vapor deposition with a mixture of methane and hydro gen gases at temperatures ranging from 520 to 700 degrees C. The density an d the length of the carbon nanotubes increased with increasing growth tempe rature. At a growth temperature of 520 degrees C, the carbon nanotubes were curly, whereas the nanotubes were straight and self-aligned upward at temp eratures above 600 degrees C. Images from high-resolution transmission elec tron microscopy showed that the nanotubes were multiwalled, with a few wall structures. The graphitized structures were also confirmed by Raman spectr a. We show that the size of Ni grains on Si substrates is correlated to the diameters of the grown carbon nanotubes. (C) 2000 American Vacuum Society. [S0734-2101(00)10004-1].