【作者】 白延虎；

【导师】 黄少铭；

【作者基本信息】 温州大学 ， 有机化学， 2008， 硕士

【摘要】 化学气相沉积法(CVD)表面生长单壁碳纳米管(SWNTs)是其器件制备和应用的基础。SWNTs可以是导体也可以是半导体,在纳米器件方面有着广泛的应用,如场效应晶体管等。但是其性能不仅取决于螺旋性也和它的直径有关。因此,如何控制它的螺旋性和直径是该领域面临的需要解决的两个重要的难题。本文通过CVD方法,对催化剂在基底表面的分散、不同催化剂、碳源等对SWNTs在基材表面的生长和直径的影响进行了研究,并对SWNTs的定向生长的机理和表面碳纳米管的转移进行了探索。(1)通过对硅基底的化学修饰来改变其表面的性质,研究了Fe/Mo纳米催化剂粒子在不同性质表面的分散规律及对SWNTs生长的影响。结果表明基底表面的疏水性的增加有助于催化剂的均匀分散,从而减少催化剂在高温下的聚集,生长的SWNTs直径较小和较均匀。同时发现定向超长SWNTs的直径要比短的无序的SWNTs小,并且催化剂在表面良好的分散可以提高定向超长SWNTs的生长效率。(2)研究了不同催化剂包括Fe/Mo、FeP、Te、Au、Ag等催化生长SWNTs的活性和所生长的碳纳米管的结构特征。结果发现Fe/Mo纳米粒子具有高的活性,Ag和Au同样具有高的催化活性,但Ag催化生长的SWNTs的直径明显比Fe/Mo催化的要小,并且更均匀,其原因是Ag在高温下相对易挥发,因此Ag是生长直径小分布窄的SWNTs的好催化剂。通过合成FeP纳米棒,在高温下分解原位形成Fe纳米粒子可以生长出小直径较均匀的SWNTs,并且可以对基底表面的修饰使FeP纳米棒在表面进行自组装获得SWNTs的网络结构或高密度膜。同时通过高温裂解有机Te的化合物首次发现Te金属具有催化生长SWNTs的能力。(3)通过选用Fe/Mo或Ag作为催化剂,采用高温裂解乙醇的方法,在硅片表面生长出了超长定向的SWNTs,并对其生长机理进行了研究,实验证明这些超长定向的SWNTs在生长过程中是以顶部生长机理在气流中悬浮生长的。同时为解决碳纳米管只能生长在硅片、石英片等耐高温的基底上的问题,本文对表面上生长SWNTs进行了转移研究,结果发现聚氨酯是很好的转移材料,可以容易的将SWNTs从硅片上转移下来,从而扩大了碳纳米管的使用范围。更多还原

【Abstract】 Growth of single-walled carbon nanotubes （SWNTs） on substrate surface by chemical vapor deposition （CVD） is the base of the fabrication and applications of the SWNTs-based devices. They can be electrical conductor or semiconductor and have potenial applications in nanoelectronics such as field effect transistor. The electrical properties of SWNTs depend on not only their helicity but also diameter. To control the diameter and helicity is still the challenge for this research area.In this thesis, the influences of many factors on the growth and the diameters of the SWNTs on substrates surface have been investigated. Those factors include the dispersion of the catalyst nanoparticles on Si/SiO₂ surface, different catalysts and different carbon sources. The growth mechanism of superlong well-oriented SWNTs is also discussed. The growth and transfer of oriented SWNTs film with high density have been also studied.（1） The surface property of Si/SiO₂ wafer can be changed by modifying the wafer with 1,1,1,3,3,3-Hexamethyldisilazane. The dispersion of Fe/Mo nanoparticles which are used as catalyst for SWNTs growth and the growth of SWNTs on bare and modified substrates have been studied. It is found that the dispersion of the catalyst nanoparticles on Si/SiO₂ wafer surface can be improved greatly from hydrophilic to hydrophobic. The diameter distribution of SWNTs depends strongly on the dispersion of the catalyst. Well dispersion of the catalyst results in uniform diameter of the SWNTs due to the decrease of the aggregation of the catalyst nanoparticles before growth. It is also interesting to find that the diameter of the superlong wel-oriented SWNTs is smaller than that of random short SWNTs. The growth yield of the long oriented SWNTs from the catalyst on fully modified wafer is much higher that from bare wafer.The results show the increase of hydrophobic property of the surface is helpful for the decentralization of catalyst and decrease the aggregation of the catalyst, so the diameter of SWNTs was small and uniform.（2） The catalytic activity for SWNTs growth by different kind of catalysts including Fe/Mo、FeP、Te、Ag and Au, and the characteristics of those nanotubes from different catalysts have been studied. The results show that Fe/Mo particles and Ag have high activity, but the diameter of SWNTs grown from Ag nanoparticles is much smaller and more uniform than that from Fe/Mo. The reson is that Ag particle is easy to vaporize at high temperature and only Ag with smaller size has catalytic activity. So Ag nanoparticle will be good catalyst for the SWNTs growth with small and uniform diameter. The FeP nanorods can be used as catalyst precursor for SWNTs growth. They can be decomposed at high temperature to form Fe nanopartices in situ, resulting uniform Fe nanoparticlrs so that uniform diameter of the nanotubes. Domain structure of SWNTs network or extremely high density of SWNTs film with uniform diameter can be generated for different application purpose by modifying the wafer surface. It is also for the first time to find that Te has catalytic activity for SWNTs growth.（3） Super-long oriented SWNTs arrays can be fabricated by using Fe/Mo and Ag as catalysts and ethanol as carbon source. The growth and orientation mechanism of the long oriented nanotubes are also discussed. The results indicate that the long nanotubes grow by top-growth mechanism and the orientation is guided by gas flow. A new method to transfer SWNTs off from Si/SiO₂ wafer by using polyurethane film has been developed. This provides a new approach to transfer nanotubes onto other substrates which are not suitable for in situ growth at high temperature.更多还原