微量水对碳纳米管形貌的影响及其机理研究

利用介质阻挡放电等离子体化学气相沉积技术，在蒸镀有25nm Ni催化剂层的Si基片上，以CH₄和H₂作为反应气体，在973K下制备了碳纳米管，并研究了微量水的引入对碳纳米管形貌的影响.场发射扫描电子显微镜结果表明，不加水时，制备出的碳纳米管直径不均匀，分布在40—90nm之间，呈链节状的结构；加入少量水时，制备出的碳纳米管直径比较均匀，集中在70nm左右，表面为瘤状结构；当水的流量进一步增加时，得到的碳纳米管表面光滑，出现了枝状结构.原位测量了加水前后等离子体区的发射光谱，分析了微量水的引入对于碳纳米管形貌变化的影响机理. 关键词： 碳纳米管 介质阻挡放电 水 发射光谱

Effect and mechanism of water on carbon nanotubes growth

Carbon nanotubes (CNTs) were grown on 25 nm Ni coated Si substrate by dielectric barrier discharge (DBD)-type plasma enhanced chemical vapor deposition (PECVD) in downstream. The temperature was 973 K and the mixture gases were methane, hydrogen and water. The contribution of water concentration on the growth of carbon nanotubes was investigated. Scanning electron microscopy (SEM) results showed that the grown CNTs in CH₄/H₂ gas mixure had chain-shaped structure and the diameter was about 40—90nm. With the addition of proper amount of water, the diameter of CNTs became uniform, and the surfaces of nanotubes were fully covered with nano-sized node-like structures. When more water was added, branched carbon nanotubes were synthesized. Optical emission spectra of the plasma during synthesis of carbon nanotubes were in-situ detected for the purpose of understanding the water effect.