Research on Precursors of Carbon Nanotubes for Control of Layer Numbers

我们已经成功地生产和纯化高品质的双壁碳纳米管（HQDWNTs）的直径分布低，很少的缺陷，通过一个新开发的高温脉冲电弧放电方法。HQDWNTs的外径分布为1.6~2.0nm，是目前最常见的双壁碳纳米管之一。这些HQDWNTs具有层间相互作用，这在正常的单壁碳纳米管（SWNTs）中不存在，并具有来自层间相互作用的新特性。对于原子级结构，HQDWNTs具有内层和外层之间的相关性。我们发现内层和外层的手性螺旋倾向于具有相同的手性螺旋，即两层都具有右手或左手结构，并且在层之间存在局部相称的石墨烯堆叠。结构的相关性还没有观察到与其他DWNTs，因为他们的结构均匀性和石墨化的壁是不够好的观察。此外，以HQDWNTs为沟道的场效应晶体管的输运特性也表现出特殊的双极特性，这也来自于HQDWNTs的层间相互作用和结构均匀性。如前所述，我们成功地控制了单壁碳纳米管和双壁碳纳米管的层数，揭示了由层间相互作用产生的双壁碳纳米管的新性质。进一步的研究正在进行中，以开发一种控制方法的层数，通过监测碳纳米管的前体与离子迁移率的方法。层的数量被确定在ms的时间范围内的纳米管生长的非常早期的阶段。离子迁移率测量是适合的测量，因为它们比传统的方法，如TEM，AFM和STM快得多。

We have succeeded to produce and purify high-quality double wall carbon nanotubes (HQDWNTs) with low diameter distribution and very few defects by a newly developed high-temperature pulsed arc discharge method. The diameter distribution of HQDWNTs is 1.6〜2.0 nm for the outer diameter, which is one of the narrowest double wall carbon nanotubes at this moment. These HQDWNTs have inter layer interaction, which does not exit in normal single-wall carbon nanotubes (SWNTs), and have novel properties coming from the layer interaction. For the atomic level structures, HQDWNTs have correlation between the inner and the outer layers. We have found that chiral helicities of the inner and the outer layers tend to have the same ones, that is, both layers have right handed or left handed structures, and that there are locally commensurate graphen stacking between the layers. The structural correlations have not been observed with other DWNTs since their structural uniformity and the graphitization of the wall are not good enough for the observations. Furthermore, transport properties of field effect transistors using HQDWNTs as channels also show the special ambipolar properties, which also come from layer interaction and structural uniformity of HQDWNTs. Now STM observation to investigate the layer interaction and details of electronic properties are in progress.As shown previously, we have succeeded to control the number of layers of SWNTs and DWNTs and to reveal the novel properties of DWNTs, which come from the layer interaction. Further researches are in progress to develop a control method for the numbers of layers by monitoring the precursors of carbon nanotubes with ion mobility method. The numbers of layers are determined very early stages of nanotubes growth in the time range of ms. The ion mobility measurements are suitable for the measurements since they are much faster than traditional methods like TEM, AFM and STM.