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纳米或十亿分之一米。碳纳米管是迄今发现的最好的导电体之一。它们承诺提高计算设备的速度和复杂性，增加商业和军用无线通信技术的带宽和能源效率，并导致新型非传统电子产品，这些电子产品不是刚性的，而是可以拉伸、滚动和折叠的。为了实现纳米管的前景，研究人员必须首先学习如何将它们组装成基板上的排列阵列。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铺展成薄膜。当衬底从槽中抽出时，纳米管在衬底上沉积并对齐。这项研究的首要目标是增加纳米管阵列的均匀性和改善其组织，从而为大面积纳米管阵列的商业应用打开大门。这些进展将使美国经济、高科技电子产业和社会受益。此外，纳米材料计量学和制造方面的努力将影响工程教育中新的材料表征本科实验室的发展。纳米管的组装通过一种称为浮动蒸发自组装的过程进行。纳米管的均匀性和组织性将通过以下方面得到改善：(1)确定在浮动蒸发自组装过程中指导纳米管组织的机制；(2)通过使用多功能聚合物包裹纳米管并在组装过程中调节纳米管之间的相互作用来控制堆积密度和纳米管之间的间距；以及(3)发展计量学来了解工艺-结构-电性能之间的联系。在初步研究中，已利用浮动蒸发自组装技术来排列使用共轭聚合物作为纳米管分化试剂制备的超高纯度半导体纳米管阵列。利用这种方法对纳米管的排列和堆积密度进行了良好的控制，使得纳米管阵列场效应晶体管的性能在导通/关断比(在恒定电导下)和导通电导(在恒定导通/关断比下)分别提高了1400倍和30-100倍。提高这些阵列的均匀性将为薄膜应用和宏电子领域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电导增加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 The nanotubes deposit and align themselves on a substrate as it is withdrawn from the trough.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.