Manufacturing Aligned Arrays of Semiconducting Carbon Nanotubes for Faster and More Energy Efficient Next-Generation Electronics

碳纳米管是完全由排列在圆柱体中的碳原子组成的纳米材料。碳纳米管的直径大约只有1纳米，也就是十亿分之一米。碳纳米管是迄今为止发现的最好的导电体之一。他们承诺提高计算设备的速度和复杂性，提高商用和军用无线通信技术的带宽和能源效率，并导致新型的非常规电子产品，这些电子产品不是刚性的，而是可以拉伸、卷起和折叠的。为了实现纳米管的前景，研究人员必须首先学会如何将它们组装成衬底上的排列阵列。该奖项支持对最近发现的制造工艺的基础研究，以实现这一目标。含有半导体碳纳米管的墨水在水槽表面被铺成薄膜。当衬底从槽中取出时，纳米管沉积并排列在衬底上。该研究的首要目标是提高纳米管阵列的均匀性和组织，为大面积纳米管阵列的商业应用打开大门。这些进步将使美国经济、高科技电子工业和社会受益。此外，纳米材料计量和制造的努力将影响工程教育中材料表征的新本科实验室的发展。纳米管的组装过程被称为漂浮蒸发自组装。通过以下方法提高纳米管的均匀性和组织性：(1)确定悬浮蒸发自组装过程中纳米管的组织机制；(2)利用多功能聚合物包裹纳米管，调节组装过程中纳米管间的相互作用，从而控制纳米管的堆积密度和间距；(3)发展计量学，了解加工-结构-电性能之间的联系。在初步研究中，利用浮动蒸发自组装技术，利用共轭聚合物作为纳米管分化剂制备了超高纯度的半导体纳米管阵列。利用这种方法，纳米管阵列的场效应晶体管的优异对准度和对封装密度的控制使其在开/关比（恒定电导）和导通比（恒定开/关比）方面的性能分别提高了1400倍和30-100倍。增加这些阵列的均匀性将为薄膜应用和宏观电子学的商业机会打开大门。进一步控制微结构将为高频线性放大器和逻辑晶体管的增加电导和商业机会打开大门。

Carbon nanotubes are nanomaterials that are comprised entirely of carbon atoms arranged in a cylinder. The diameter of a carbon nanotube is only about 1 nanometer or 1 billionth of a meter. Carbon nanotubes are among the best conductors of electricity that have ever been discovered. They promise to increase the speed and complexity of computing devices, increase the bandwidth and energy efficiency of commercial and military wireless communications technologies, and lead to new types of unconventional electronics that are not rigid but can be stretched, rolled, and folded. To realize nanotubes' promise, researchers must first learn how to assemble them into aligned arrays on substrates. This award supports fundamental research on a recently discovered manufacturing process for achieving this goal. Inks containing semiconducting carbon nanotubes are spread into thin films on the surface of a water trough. The nanotubes deposit and align themselves on a substrate as it is withdrawn from the trough. The overarching objective of the research is to increase the uniformity and improve the organization of the nanotube arrays to open the door for large-area nanotube array manufacturing for commercial applications. These advances will benefit the U.S. economy, high-tech electronics industries, and society. Moreover, the efforts on nanomaterials metrology and manufacturing will impact the development of new undergraduate laboratories on materials characterization for engineering education.The nanotube assembly occurs via a process called floating evaporative self-assembly. The uniformity and organization of nanotubes will be improved by: (1) determining the mechanisms that direct nanotube organization during floating evaporative self-assembly; (2) controlling packing density and inter-nanotube spacing by using multifunctional polymers to wrap the nanotubes and mediate inter-nanotube interactions during assembly; and (3) developing metrology to understand the link between processing-structure-electrical properties. In preliminary research, floating evaporative self-assembly has been exploited to align arrays of ultrahigh purity semiconducting nanotubes prepared using conjugated polymers as nanotube-differentiating agents. The excellent degree of alignment and control over the packing density of the nanotubes using this method has led to gains in nanotube array field effect transistor performance of 1400x in on/off ratio (at constant conductance) and 30-100x in on-conductance (at constant on/off ratio). Increasing the uniformity of these arrays will open the door for commercial opportunities in thin film applications and macroelectronics. Further controlling the microstructure will open the door for increased conductance and commercial opportunities in high-frequency linear amplifiers and logic transistors.