Study of precise on structural control of carbon nanotubes

针对单壁碳纳米管(SWCNTs)在晶体衬底上的CVD生长，探讨了以铁素体为催化剂在蓝宝石衬底上自定向生长的机理。我们对特殊设计衬底上的生长行为的分析表明，定向生长是由针尖生长机制引起的。这一结论被蓝宝石衬底上生长的单壁碳纳米管的原位扫描电子显微镜观察所证实。利用拉曼光谱对CVD生长过程进行了原位观察，研究了单壁碳纳米管的手性分辨生长动力学。首次清晰地探测到生长中的单壁碳纳米管的径向呼吸模式的拉曼信号。我们对生长动力学的详细分析阐明了单壁碳纳米管的手性、催化剂直径和生长时间之间的关系。在超高压兼容的气源分子束外延系统中，以乙醇为碳原料，在非常清洁的条件下生长了单壁碳纳米管。生长的单壁碳纳米管的化学状态为特征…用原位X-射线光电子能谱对其进行了进一步细化。从光谱分析中发现，Co催化剂颗粒在CVD生长后仍保持“金属状态”，这与通常的VLS生长机理相反，而Fe催化剂在更高的温度下CVD生长后部分形成氧化物，这解释了Fe催化剂的SWCNTs的产率比Co催化剂低的原因。通过蒸发来自铁蛋白的颗粒(直径3-5 nm，焙烧后即刻)制备了直径小于2 nm的超细金属纳米颗粒。通过单壁碳纳米管的直径与催化剂颗粒之间的相关性，提出了单壁碳纳米管直径控制的可能性。单壁碳纳米管是由新型的无催化活性的催化剂材料合成的，如硅、锗、碳化硅的半导体纳米颗粒和金、银、铜的贵金属纳米颗粒。在这些现象的基础上，我们提出了一种新的生长机制，它将开启手性控制的可能性。较少

For the CVD growth of single-walled carbon nanotubes(SWCNTs) on crystalline substrates, the mechanism of self-directional growth on sapphire substrates was explored by using ferritins as growth catalysts. Our analysis of growth behavior on the specially designed substrates indicates that the directional growth is caused by the tip-growth mechanism. This conclusion was confirmed by in-situ SEM observation of the SWCNT growth on sapphire substrates. Chirality-resolved growth kinetics of SWCNTs was investigated by in situ observation of the CVD growth process using Raman spectroscopy. The Raman signals of radial breathing modes from growing SWCNTs were clearly detected for the first time. Our detailed analysis of the growth kinetics clarified the correlation among SWCNT chirality, catalyst diameter and growth duration.SWCNTs were grown under very clean conditions in a UHV-compatible gas-source MBE system using alcohol as carbon feedstock. The chemical states of grown SWCNTs were character … More ized by in-situ X-ray photoelectron spectroscopy. From the analysis of the spectra, we found that Co catalyst particles maintain "metallic states" even after CVD growth, contrary to the ordinary VLS growth mechanism, and that Fe catalysts partially form oxides after CVD growth at higher temperature, which explains the very low yield of SWCNTs for Fe catalyst compared with Co catalyst.Very fine metal nanoparticles(diameter of less than 2 nm) were prepared by evaporation of particles(diameter of 3-5 nm, just after calcination) derived from ferritin. The possibility of SWCNT diameter control is suggested by the correlation between diameters of SWCNTs and the catalyst particles. SWCNTs were synthesized from novel catalyst materials, which have been considered to have no catalytic activity, such as semiconductor nanoparticles of Si, Ge, SiC, and noble metal nanoparticles of gold, silver, copper. On basis of these phenomena, we proposed a new growth mechanism that will open up the possibility of chirality control. Less