Thermal CVD synthesis of single-walled carbon nanotubes on substrates for optical and thermal device applications

单壁碳纳米管（SWNTs）由于其独特的电特性、极高的热导率和机械强度，被广泛应用于光学、热学、电学、扫描探针显微镜、高强度材料和导电复合材料等领域。为了早日实现应用，在基底上合成高纯度的单壁碳纳米管将是有益的。在本课题中，通过对本课题组开发的醇催化CVD法进行扩展，开发出了在石英和硅衬底上合成单壁碳纳米管的方法。几年前，单壁碳纳米管的合成通常使用氢氧化碳或一氧化碳作为碳源。通过使用醇作为碳源，我们先前表明，它是可能的，在相对较低的温度下生长高纯度的单壁碳纳米管。由于直接在硅或石英衬底上合成单壁碳纳米管有利于热处理， ...更多信息 铝和光学器件的应用，在这个项目中，我们已经建立了浸涂法，其中钴/钼醋酸盐涂覆在基板上，然后热氧化形成均匀尺寸的催化纳米颗粒。利用该技术，我们成功地制备了垂直取向的单壁碳纳米管薄膜，并通过测量CVD生长过程中的激光吸收，实现了对垂直取向单壁碳纳米管（VA-SWNT）薄膜厚度的真实的实时识别。通过在各种实验条件下从膜厚度的时间历程量化催化剂的初始活性和寿命，发现生长过程由一级化学反应控制。此外，我们还通过对实验结果的研究以及对生长过程的分子动力学模拟，对生长机理进行了讨论。在此基础上，优化了醇催化CVD工艺条件，成功制备了厚度大于20 μ m的VA-SWNT薄膜，并对VA-SWNT薄膜的拉曼光谱和UV/1 R吸收光谱进行了测试。通过偏振拉曼光谱确定VA-SWNT薄膜特有的径向呼吸模式，建立了一种检查SWNT薄膜取向的方法。还阐明了单壁碳纳米管独特的偏振光吸收特性。少

Single-walled carbon nanotubes (SWNTs), due to their unique charilty-dependent electrical properties, extremely high thermal conductivity and high mechanical strength, are proposed for various applications ranging from optical, thermal, electrical devices to tips of scanning probe microscopes, high strength materials and conductive composite materials. For early realization of the applications, it would be beneficial to synthesize high-purity SWNTs on substrates. In the current project, by extending the alcohol catalytic CVD method previously developed in the group, we have developed a method to synthesize SWNTs on quartz and silicon substrates.Until several years ago, carbon hydrates or carbon monoxide had been commonly used as carbon sources for SWNT syntheses. By using alcohol as the carbon source, we previously showed that it is possible to grow high purity SWNT at relatively low temperature. As it is beneficial to synthesize SWNTs directly on silicon or quartz substrates for therm … More al and optical device applications, in this project, we have established a dip-coating method, where Cobalt/Molybdenum acetate is coated on the substrate then thermally oxidized to form uniform-size catalytic nano-particles. With this dip-coating technique, we have succeeded in synthesizing a film of SWNTs aligned vertically with respect to the substrates.Furthermore, by measuring the laser absorption during the CVD growth process, real time identification of the thickness of vertically aligned SWNT (VA-SWNT) films was realized. By quantifying the initial activity and lifetime of catalysts from the time histories of the film thickness at various experimental conditions, it was found that the growth process is governed by a first order chemical reaction. In addition, we have discussed the growth mechanisms by studying the experimental results together with the molecular dynamics simulations of the growth process. With the knowledge learnt in the above studies, experimental conditions of the alcohol catalytic CVD process were optimized and, as a result, stable and repeatable syntheses of over 20 micrometer thick VA-SWNT films have been realized.Finally, Raman spectra and UV/1R optical absorption spectra of VA-SWNT films were measured. A method to check the alignment of the SWNT film was established by identifying a radial breathing mode that is unique to VA-SWNT film with polarized Raman spectroscopy. Unique polarized optical absorption characteristics of SWNTs were also clarified. Less