Controlling Charge Transport of Organic Semiconductors and Molecules via Edge-On Gating Effect

摘要本项目主要研究分子晶体管模型的合成及其物理性质的研究。该研究有助于找到解决电子系统小型化所面临的限制的答案。这些分子系统的合成方法被证明是可行的，单分子电测量技术是可行的。初步结果表明，适当的化学功能可以开关电流，类似于晶体管的功能。在材料研究部固态与材料化学项目的支持下，该研究团队正在进行广泛的合成工作，以制备一系列具有不同结构和功能的新化合物。进行理论研究以计算和理解分子的电学性质。该项目为学生提供了一个良好的教育平台，特别是一个有效的孵化器，鼓励少数民族学生走上科研的职业道路。这个项目包括一个招收这些学生的计划。这项工作是一项跨学科的努力，将化学、材料科学、物理和纳米科学结合起来，探索新的科学和材料，并需要在合成方法和现代表征技术的应用方面进行广泛的创新，以深入了解分子材料的电子特性。因此，它为学生提供了广泛的研究和教育机会。在这个项目中工作的学生获得必要的知识和培训，成为有机/材料化学和有机电子材料领域的未来领导者。产生的新材料可能对电子工业产生潜在影响。技术摘要本项目旨在合成基于环式结构基序的分子晶体管模型，并研究边对化学门控效应对半导体分子和材料电子性能的影响。环烷部分包含一个垂直的吡啶单元，该单元通过两个乙烯基连接到共轭半导体分子。因此，吡啶环中的pi系与半导体线中的pi系是正交的。门控端不直接与半导体实体共轭，非常类似于FET中的栅极电极。开发的分子系统类似于场效应晶体管，但允许使用断结扫描隧道光谱技术来研究门控效应。研究重点是在垂直吡啶环的对位上引入具有不同电子性质的各种官能团的边向化学门控效应。这些取代基的行为就像施加的门控电压，允许详细的物理研究，以深入了解在控制电荷输运。本项目投入了大量的合成工作，以制备一系列具有不同门控部分、共轭长度和电子性质的新化合物。该团队建立了扫描隧道光谱系统来表征分子的电荷传输行为，包括单分子电导、电子隧道势垒和与官能团的化学门控关系。理论研究有助于计算和理解门控吡啶部分的电荷密度变化，这被证明是与电荷传输电导相关的一个参数。对门控效应的可能应用进行了探讨，包括质子触发开关和光感应开关

Non-technical AbstractThis project is focused on synthesis of model molecular transistors and investigation of their physical properties. The research can help to find answers for the limitations faced in miniaturization of electronic systems. Synthetic approaches to these molecular systems are shown to be feasible and techniques for electric measurements on single molecules are operational. Preliminary results indicate proper chemical functions can switch electric current on and off, similar to functioning of transistors. With support from the Solid State and Materials Chemistry program in the Division of Materials Research, this research team is pursuing extensive synthetic efforts to prepare a series of new compounds with different structures and functions. Theoretical studies are performed to calculate and understand the electric properties of molecules. This project provides an excellent educational platform for students, especially an effective incubator to encourage minority students into a career path of scientific research. This project includes a plan for recruiting these students. The proposed work is an interdisciplinary effort that integrates chemistry, materials science, physics and nanoscience to explore new science and materials, and requires extensive innovations in synthetic approaches and applications of modern characterization techniques to gain insight into the electronic properties of molecular materials. It thus offers a broad spectrum of research and educational opportunities for students. Students working in this program gain necessary knowledge and training to be future leaders in the area of organic/material chemistry and organic electronic materials. New materials generated can have potential impact on electronic industries.Technical AbstractThis project is aimed at synthesis of model molecular transistors based on cyclophane building motif, and investigating the edge-on chemical gating effect on electronic properties of semiconducting molecules and materials. The cyclophane moiety contains a perpendicular pyridine unit that is connected to the conjugated semiconducting molecules with two vinyl groups. Thus, the pi-system in pyridine ring is orthogonal to that in semiconducting wire. The gating end is not directly conjugated with the semiconducting entity, closely resembling a gate electrode in FET. The molecular system developed resembles a field effect transistor, but allows using break-junction Scanning Tunneling Spectroscopy techniques to investigate the gating effect. The research effort is focused on edge-on chemical gating effect, by which various functional groups with different electronic properties are introduced to the para-position of the perpendicular pyridine ring. These substituents behave like applied gating voltage, allowing for detailed physical investigation to gain insight into in controlling charge transport. This project devotes extensive synthetic efforts to prepare a series of new compounds with different gating moieties, conjugation lengths, and electronic properties. This team has set up a Scanning Tunneling Spectroscopy system to characterize the charge transport behavior of molecules, which include single molecular conductance, electron tunneling barriers and chemical gating correlation with functional groups. Theoretical studies help to calculate and understand the charge density changes in the gating pyridine moiety, which was shown to be a parameter correlated to the charge transport conductance. Ideas for possible applications of the gating effect are pursued, including proton triggered switch and photoinduced switch