Electro-Optics of Single-Walled Carbon Nanotube Thin Films: Physics and Applications

单壁碳纳米管薄膜的电光特性：物理与应用。非技术总结单个半导体单壁碳纳米管(SC-SWNTs)因其高迁移率、高载流能力和低本征电容而成为理想场效应晶体管。基于由单个半导体单壁碳纳米管组成的通道的器件的开发仍然是一个活跃的研究领域，因为该技术对SC-SWNTs的材料纯度(直径、手性和排除金属SWNTs的必要性)提出了严格的要求，并将单个器件组装成完全布线的超大规模集成电路(VLSI)。在这方面，本项目中建议研究的SC-SWNT薄膜形成了一个特别吸引人的目标，因为这种薄膜很容易通过简单的台式实验室技术来制备，包括过滤、喷雾、滴注和冲压，并且通过仔细控制制备条件，很容易制备出厚度在1到1000 nm之间的灵活的、可转移的SC-SWNT薄膜。本提议旨在通过在门控场效应晶体管器件中使用适当选择的有机掺杂剂和离子液体来将单个SC-SWNT器件的突出的工程和物理性能扩展到化学工程的SWNT薄膜，从而进一步推动这一薄膜技术的发展。在选择研究的功能光电元件中，有电光调制器、光电探测器和光发射器。对增强的Franz-Keldysh效应的实验观察可能导致新一代电光调制器能够在高速、高效和低电压下工作。基于最近观察到的离子液体包覆的单壁碳纳米管薄膜沟道中强烈的内部电场，形成p-n结的新策略将被用来提高单壁碳纳米管的光电导性。在过去柔性电子学和智能窗的应用中，SWNT薄膜通常被用作被动透明电极；本方案将探索将SWNT薄膜用作智能窗和电可配置光学介质的有源电致变色层的可行性。这项拟议的工作将刺激基于单壁碳纳米管薄膜和基于薄膜的柔性电子学的新光电子学领域的发展，这将增加美国的技术和经济竞争力。技术总结建议从实验上探索半导体单壁碳纳米管(SC-SWNTs)薄膜中的电光现象及其器件应用。单壁碳纳米管薄膜是研究电光现象的理想介质，因为它们具有与单个单壁碳纳米管相同的基本物理性质，而且还允许应用各种表征技术，并为开发基于单壁碳纳米管薄膜的新型电光器件提供了可能性。该项目侧重于半导体单壁碳纳米管的应用，这项工作建立在该领域的最新发展基础上，如单壁碳纳米管测辐射热光探测器、光耦合器、电光调制器和电可重构光学介质。拟议的新实验包括：(I)通过在取向的单壁碳纳米管薄膜上施加强大的纵向电场来实现增强的Franz-Keldysh效应；(Ii)利用离子液体诱导的静电掺杂制备单壁碳纳米管p-n结，用于开发光电探测器和光发射器；(Iii)探索单壁碳纳米管薄膜作为空间调制红外透明的电配置光学介质和作为智能窗户的有源电致变色层的能力。

Abstract - Electro-Optics of Single-Walled Carbon Nanotube Thin Films: Physics and Applications. NON-TECHNICAL SUMMARYIndividual semiconducting single-walled carbon nanotubes (SC-SWNTs) constitute the ideal field effect transistor as a result of their high mobilities, high current carrying capacity and low intrinsic capacitance. The development of devices based on a channel composed of a single semiconducting single-walled carbon nanotube continues to be an active area of research due to the stringent requirements that this technology places on the material purity of the SC-SWNTs (diameter, chirality and the necessity to exclude metallic SWNTs), and assembly of individual devices into fully wired very large scale integrated (VLSI) circuits. In this respect the SC-SWNT films proposed for study in the present project form a particularly appealing target because such films are readily prepared by simple bench top laboratory techniques that include filtration, spraying, drop-casting and stamping and by careful control of the preparative conditions, readily allow the reproducible fabrication of flexible, transferrable SC-SWNT films with thicknesses that range from 1 to 1000 nm.The present proposal aims to further this thin film technology by extending the outstanding engineering and physical properties of single SC-SWNT devices to chemically engineered SWNT thin films by use of suitably chosen organic dopants and ionic liquids in gated field effect transistor devices. Among the functional optoelectronic components selected for study are electro-optical modulators, photodetectors and light emitters. The experimental observation of the enhanced Franz-Keldysh effect may lead to a new generation of electro-optical modulators capable of operating at high speed, high efficiency and low voltage. The new strategy of p-n junction formation, based on the recent observation of strong internal electric fields in SWNT thin film channels coated with ionic liquids, will be used to enhance the photoconductivity in SWNTs. In past flexible electronics and smart window applications, SWNT thin films were usually explored as passive transparent electrodes; this proposal will explore the feasibility of utilizing SWNT thin films as active electrochromic layers for smart windows and electrically configurable optical media. The proposed work will stimulate the development of a new field of optoelectronics based on SWNT thin films and thin film based flexible electronics which will increase the technological and economic competitiveness of the United States.TECHNICAL SUMMARYIt is proposed to experimentally explore the physics of electro-optical phenomena in films of semiconducting single-walled carbon nanotubes (SC-SWNTs) and their device applications. The SWNT thin films constitute the ideal medium for studying electro-optical phenomena, because they possess the same fundamental physical properties as individual SWNTs, but also allow the application of a variety of characterization techniques and offer the possibility of the development of a new class of SWNT thin film based electro-optical devices. The project focuses on the application of semiconducting SWNTs and the work builds on recent developments in this area such as the SWNT bolometric photodetector, optocoupler, electro-optical modulator and electrically reconfigurable optical media. Proposed new experiments include: (i) the realization of the enhanced Franz-Keldysh effect by the application of strong longitudinal electric fields to films of aligned SWNTs; (ii) the fabrication of SWNT p-n junctions utilizing electrostatic doping induced by an ionic liquid for the development of photodetectors and light emitters; (iii) exploration of the ability of SWNT thin films to function as electrically configurable optical media of spatially modulated infrared transparency and as the active electrochromic layer for smart windows.