Synthesis of uniformly distributed carbon nanotubes on a large area of Si substrates by thermal chemical vapor deposition

We have synthesized carbon nanotubes by thermal chemical vapor deposition of C₂H₂ on transition metal-coated silicon substrates. Multiwalled carbon nanotubes are uniformly synthesized on a large area of the plain Si substrates, different from previously reported porous Si substrates. It is observed that surface modification of transition metals deposited on substrates by either etching with dipping in a HF solution and/or NH₃ pretreatment is a crucial step for the nanotube growth prior to the reaction of C₂H₂ gas. We will demonstrate that the diameters of carbon nanotubes can be controlled by applying the different transition metals.