NER: Field Effect Transistor Using Long Conjugated Semiconducting Molecular Wires

0210501Guo本提案是对NER类别中的纳米科学与工程计划NSF 01-157的响应。该方案的重点是研究一类特殊的分子，即共轭聚合物导线的电学性质，并实现基于场效应的晶体管结构。基于有机材料的设备已被确定为未来电子产品的一种替代方案。分子电子学的吸引人的特点是它提供了在分子水平上研究一组新材料的机会，同时也为我们提供了一种全新的微纳电子技术。目前有机电子学的研究有两个领域，一个是分子电子学，另一个是有机薄膜晶体管。在分子电子学领域，已经有几个成功的实验工作装置的演示。然而，分子电子器件应用中最大的挑战之一是难以将单个分子连接起来形成功能电路。因此，分子器件的实际应用主要针对存储电路，其中电路的布局相对简单。在另一个领域，基于共轭聚合物和低聚物的有机薄膜晶体管(TFT)的研究已经进行了十多年，并被设想为更传统的a-Si TFT的替代品。然而，这些有机薄膜的极低迁移率给其实际应用带来了巨大的挑战，并严重限制了其实际应用。认识到这两个方面的技术困难，我们建议使用三种类型的共轭大分子来实现晶体管结构。这些分子是半导体共轭聚合物，呈长刚性线的形式。PI将合成和制造器件，使分子的两端与源/漏电极共价键合。通过对这种类型的分子晶体管的系统研究，他们希望解决这些半导体导线是否能为实际应用提供足够的电导和驱动能力等器件性能问题，以及它们基于场效应晶体管的工作原理实现简单分子电路的可扩展性。与传统半导体器件相比，分子线的一个显著特点是其响应可能由量子相干效应主导，甚至可能在高温下也是如此。因此，提出的分子线晶体管也有助于理解此类结构中输运现象的许多悬而未决的问题。他们相信，凭借先进的纳米制造技术和NER团队的有机合成专业知识，他们将处于独特的地位，可以实现所提出的分子线晶体管，并研究这一新类别的分子电子学中的各种输运性质。

0210501GuoThis proposal was received in response to the Nanoscale Science and Engineering Initiative, Program Solicitation NSF 01-157, in the NER category. The focus of this proposal is to study the electrical properties of a special class of molecules, namely, conjugated polymer wires, and to implement transistor structures based on the field effect. Devices based on organic materials have been identified as one alternative for future electronics. The attractive features of molecular electronics are that it provides an opportunity to study a new group of materials on the molecular level, while offering us a whole new micro- and nanoelectronics technology. Currently there are two areas of research in organic electronics, one is molecular electronics, and the other is organic thin film transistor. In the molecular electronics area, there have been several successful demonstrations of experimental working devices. One of the biggest challenges, however, in the application of molecular electronic device is the difficult in connecting individual molecules to form functional circuits. As a result, practical applications of molecular devices have been primarily aimed at memory circuits, where the circuit's layout is relatively simple. In another area, researches on organic thin film transistors (TFTs) based on conjugated polymers and oligomers have been conducted for over a decade, and have been envisioned as an alternative to the more traditional a-Si TFTs. However the extremely low mobility of these organic films has presented an immense challenge, and placed serious limitation to its practical application. Recognizing the technical difficulty in these two ends, we propose to use three types of conjugated macromolecules to implement transistor structures. These molecules are semiconducting conjugated polymers that are in the form of long rigid wires. The PIs will synthesize and fabricate the device such that the two ends of the molecule will covalently bond to the source/drain electrodes. Through a systematic study of this type of molecular transistor, they would like to address both the device performance issues such as whether these semiconducting wires can offer sufficient conductance and drive capability for practical applications, as well as their extendibility to implement simple molecular circuits based on the operation principle of field effect transistor. In comparison with conventional semiconductor devices, a remarkable aspect of molecular wires is that their response may be dominated by quantum coherence effect, possibly even at high temperature. So the proposed molecular wire transistor can also help to understand many outstanding questions on transport phenomenon in such structures. They believe that with advanced nanofabrication technologies and the organic synthesis expertise of this NER team, they are in a unique position to realize the proposed molecular wire transistor, and to study various transport properties in this new class of molecular electronics.