Study on Growth Mechanism of Carbon Nanotubes Grown Using Self-Organized Catalyst Nanoclusters

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Carbon nanotube (CNT) has been synthesized by chemical vapor deposition (CVD), arc discharge, laser vaporization and so on. So far the growth mechanism of the CNT has been proposed. In the proposed mechanism, the key steps are the formation and liquefaction of the catalyst nanoparticles. However, the growth mechanism of CNT has not been fully elucidated. In this project, self-organized catalyst nanoparticles are used as a nucleation seed of the CNT with the aim of investigating the growth mechanism of CNT. It is known that the properties of metal nanoparticles such as size, shape, crystallinity, or crystallographic plane are well-controlled using hydrogen-induced self-organization. The new findings worthy of special mention are as follows.(1) We successfully synthesized CNTs with different orientations using self-organized catalyst metal nanoparticles by CVD. By optimizing the growth conditions, lateral or vertical growth of the CNTs was demonstrated against the substrates. Moreover, it was found that assisting plasma during CVD improved the vertical alignment of the CNTs.(2) The structural properties of the grown CNTs with different orientations against the substrates were characterized. Based on the TEM observation for the CNTs, a new growth model was proposed. In the model, the shape of the self-organize catalyst nanoparticles considerably affects the growth of the CNTs. The field electron emission (FE) property for the obtained CNTs was also investigated. As a result, the randomly oriented CNTs exhibited better FE property, indicating the surface defect could be an emission site on the CNTs.