Synthesis of high-density carbon nanotube films by microwave plasma chemical vapor deposition

Nanotubes with diameters ranging from 20 to 400 nm and densities in the range of 10(8)-10(9) cm(-2), produced on metal-coated silicon by microwave plasma chemical vapor deposition, show various shapes depending upon: (i) growth conditions, and (ii) pre-or post-growth treatment of the samples. Presence of nitrogen in the growth or pre-growth atmosphere increases the density and vertical growth rate of nanotubes. The growth rate on an iron-coated substrate is higher than on a nickel-coated substrate. A cleaning procedure, consisting of ultrasonic treatment of nanotubes in methanol, is demonstrated. (C) 2001 Elsevier Science B.V. All rights reserved.