Controlled growth of high quality bamboo carbon nanotube arrays by the double injection chemical vapor deposition process

Large area of vertically aligned bamboo-structured carbon nanotubes (CNTs) films was grown on quartz substrates by the injection CVD reactions using a double injection regime involving separate injection of a hydrocarbon liquid and a promoter. Excellent arrays of all bamboo carbon nanotubes were obtained using ethanol as the carbon source by this reaction design. Arrays of the bamboo nanotubes were obtained also using toluene and pyridine in replace of ethanol as the carbon source. A high growth rate of the film which is double of that reported earlier, was obtained by controlling the ratio of ethanol and ethylenediamine, with the film thickness attained 160 mu m after the growth for 20 min. We found that ethylenediamine played a key role in the formation of the bamboo structures. When a single injection was used in absence of ethylenediamine, the reaction could still yield the arrays of nanotubes which, however, of the normal tubule structures rather than the bamboos structures. The fine structures of the bamboo nanotubes changed with the sort of the carbon source, the carrying gases and the synthesis temperatures. The present double injection CVD reactions allow the use of mutually insoluble hydrocarbons and promoters, avoiding the possible reactions among the reactants, and, more importantly, provides the feasible control over the nanotube arrays from the tubule to the bamboo structures. (C) 2007 Elsevier B.V. All rights reserved.