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

碳纳米管（CNT）的制备方法有化学气相沉积法（CVD）、电弧放电法、激光蒸发法等，目前已提出了CNT的生长机理。在所提出的机理中，关键步骤是催化剂纳米颗粒的形成和液化。然而，CNT的生长机制尚未完全阐明。本计画以自组织触媒奈米粒子作为碳纳米管的成核种子，探讨碳纳米管的成长机制。众所周知，金属纳米颗粒的性质，如尺寸、形状、结晶度或晶面，可以通过氢诱导的自组织得到很好的控制。值得特别提及的新发现如下。(1)我们成功地合成了不同取向的碳纳米管使用自组织催化剂金属纳米粒子的化学气相沉积。通过优化的生长条件，横向或垂直生长的碳纳米管被证明对基板。此外，有人发现，辅助等离子体在CVD过程中提高了碳纳米管的垂直排列。(2)对生长的碳纳米管的结构特性与不同的取向对基板进行了表征。基于对碳纳米管的TEM观察，提出了一种新的生长模型。在模型中，自组织催化剂纳米颗粒的形状显著影响碳纳米管的生长。并对所制备的碳纳米管的场致电子发射性能进行了研究。结果表明，无规取向的碳纳米管表现出更好的FE性能，表明表面缺陷可能是碳纳米管上的发射位点。

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.