Growth of carbon nanotubes by microwave plasma chemical vapor deposition using CH4 and CO2

Carbon nanotubes (CNTs) were grown vertically and aligned on Fe catalytic nanoparticles which were deposited on a Si substrate at low temperature using CH4 and CO2 gas mixtures. A dynamic form of optical emission spectroscopy was used to C detect the species in the plasma. These data show the dominant species in gas phase reaction. The composition of plasma significantly affects the reaction mechanism of CNTs growth and diamond film synthesis. The growth quality of CNTs is better C than a conventional reaction in a gas mixture of hydrogen and hydrocarbons. However, the highest yield of CNTs of approximately 70% was obtained by microwave plasma chemical vapor deposition for CH4-CO2 gas mixture at a flow rate of CH4/CO2 at 96%, power supply of 300 W, reaction time of 20 min and bias voltage of 150 V In summary, the oxygen containing in the CH4-CO2 gas system can increase the amount of C-2 In the C-2-rich plasma the excited C-2 emission at a higher intensity is beneficial to graphite deposition, which enhances CNTs synthesis on catalyst-deposited surface quality. (C) 2002 Elsevier Science B.V. All rights reserved.