部分碳包覆金属催化剂控制生长带隙可调的窄手性分布单壁碳纳米管

Semiconducting single-wall carbon nanotubes (SWCNTs) have high carrier mobility, high on/off radio, small size, excellent flexibility, therefore, they are considered to be one of the most promising candidates for use in next generation electronic devices. However, the practical application of SWCNTs in electronics has been hindered by the fact that it is difficult to prepare semiconducting SWCNTs with high quality and uniform property. In this application, we propose to prepare semiconducting SWCNTs with narrow chirality distribution and tunable bandgap by combined catalyst-structure design and in-situ selective etching. Monodispersed, uniform, partially carbon-coated alloy nanoparticles are prepared by a block copolymer self-assembling method. The partial carbon coating layer makes SWCNTs grow following a perpendicular mode, and prevents the nanoparticles from aggregation. The high-melting point nanoalloys keep their crystalline structure at high temperatures, and grow narrow-chirality distributed SWCNTs controllably. Hydrogen is introduced as an etchant to remove metallic SWCNTs with higher chemical reactivity. As a result, semiconducting SWCNTs with high quality and highly uniform structure and performance can be obtained. By further adjusting the size of catalyst nanoparticles and the area of partial carbon-coating layer, semiconducting SWCNTs with tunable bandgap can be obtained. The relationship between the catalyst structure, growth kinetics and SWCNT chirality will be explored by in-situ environmental transmission electron microscopy study. And the controlled-growth mechanism will be revealed by combined theoretical calculations.

半导体性单壁碳纳米管(SWCNT)因具有高载流子迁移率、高开关比、小尺寸及柔性而可望用于下一代电子器件中，但目前仍无法控制生长高质量、高均一性半导体性SWCNT。本项目提出一种催化剂结构设计与选择性刻蚀相结合可控制备带隙可调、窄手性分布的半导体性SWCNTs的方法。采用嵌段共聚物自组装法制备单分散、尺寸均一、高温稳定的部分碳包覆合金纳米颗粒催化剂。部分碳包覆结构使SWCNT以垂直模式生长并抑制纳米颗粒的团聚；结构稳定的高熔点合金纳米颗粒控制生长窄手性分布的SWCNT；在生长过程中引入刻蚀剂选择性去除金属性SWCNT，从而获得高质量、高结构和性能均一性的半导体性SWCNT。通过调控催化剂的尺寸分布及部分碳包覆暴露部分的面积生长带隙可调的SWCNT。利用原位透射电镜研究催化剂结构、组分及反应动力学条件对SWCNT手性的影响规律，结合理论计算揭示其可控生长机理。

单壁碳纳米管（SWCNT）因具有高载流子迁移率、高导电性、纳米管腔和优异的力学性能，有望应用于下一代电子器件中。然而，不同直径和螺旋角的SWCNT具有不同的手性，导致其既有金属性也有半导体性。难以高效生长结构均一的SWCNT，严重制约了其在纳电子器件中的应用。基于此，本项目以催化剂设计结合原位刻蚀的方法制备了窄手性分布SWCNT，并探讨了刻蚀性气体及催化剂结构均一性对可控生长结构均一SWCNT的作用。采用嵌段共聚物自组装的方法制备了单分散、尺寸均一的Fe和高熔点的Ru金属纳米颗粒；以Fe纳米颗粒为催化剂，H2为刻蚀剂直接生长了高质量半导体性SWCNT；以小尺寸、高温稳定的Ru纳米颗粒为催化剂，无氢条件下生长了窄手性分布SWCNT；透射电镜观察结合分子动力学模拟揭示了刻蚀剂H2在SWCNT形核生长中的重要作用；以成分可调、高温稳定、高催化活性的WCoTa为模型催化剂，系统讨论了化学气相沉积中热力学和动力学因素对生长窄手性分布SWCNT效率的影响。本项目通过系统研究影响SWCNT的生长条件，获得了结构均一的SWCNT，并揭示了可控生长机理，为SWCNT在纳电子器件领域的应用奠定了材料基础。