Growth of Millimeter-Scale Vertically Aligned Carbon Nanotubes by Microwave Plasma Chemical Vapor Deposition

Abstract

Millimeter-scale, vertically aligned carbon nanotubes (CNTs) were grown at a relatively low temperature of 700 °C by the microwave plasma chemical vapor deposition. Oxygen and water were used to investigate their role in the growth rate and crystallinity of CNTs. Scanning electron microscopy and transmission electron microscopy were adopted to observe the height and number of walls of the CNTs, respectively. The addition of oxygen significantly increased the growth rate of CNTs (∼23 µm/min) for 70 min, which is three and two times higher than that of normal CNTs and water-assisted CNTs, respectively. Furthermore, the high growth rate was maintained for 220 min and the crystallinity of CNTs, which was evaluated by the G to D band ratio in Raman spectra, was also greatly improved only by introducing oxygen.