Charge Tunneling in Organic Matter

化学系的大分子、超分子和纳米化学（MSN）项目正在资助哈佛大学的George Whitesides教授研究控制电流通过通常是电绝缘的薄层材料的方法。当这些材料足够薄（1-2纳米，或小于20个原子的厚度）时，它们允许电荷通过一种完全不同的称为隧穿的过程穿过。在隧道中，电荷面对一个通常绝缘的屏障，直接穿过它。为了理解电荷通过通常绝缘的有机物质隧穿，本项目追求三个目标：设计增强或减少隧穿的新材料；向参与该项目的学生介绍一种需要从有机合成和材料科学到量子物理的综合技能的科学风格，并加强美国的技术队伍；设计、建造和演示用于研究隧道的新工具，这些工具广泛有用，并且足够简单，可以在本科学院的科学教学中使用。这个项目的目的是了解电荷穿过薄的绝缘有机薄膜的隧道。它将使用专门为此目的开发的结，它有三部分：i)扁平金或银的电极；ii)有机或有机金属化合物（或作为隧道屏障的化合物混合物）的自组装单层（SAM）； iii)第二电极，包括由一滴液态共晶镓铟合金组成的柔顺结构，上面覆盖着一层薄薄的氧化镓导电膜。该项目将在低电压（V ~ 0.5V）下测量穿过该结的隧道电流，使用一些设计用于测试与隧道速率有关的理论的SAMs，以及发生隧道的分子的分子和电子结构。该项目将有两个目标：i)验证足以解释隧道掘进速度的理论水平；Ii)利用这一理论预测新型的隧穿机制，以及涉及到有机物隧穿的新现象。这项工作的预期结果是对轨道结构的基本理解，特别是最高能量占据的分子轨道，或HOMOs和它们之间的电子耦合，导致特别高或特别低的电荷隧穿率。这两种结果都很有趣，而且最终都可能在分子电子和有机电子器件的设计中有用。

With this award, the Macromolecular, Supramolecular and Nanochemistry (MSN) Program of the Division of Chemistry is funding Professor George Whitesides of Harvard University to investigate methods to control the flow of electrical currents through thin layers of materials that are normally electrically insulating. When these materials are sufficiently thin (1-2 nanometers, or less than 20 atoms in thickness), they allow electrical charge to cross by a fundamentally different process called tunneling. In tunneling, the charge, faced with a normally insulating barrier, simply passes through it. In understanding tunneling of charge through normally insulating organic matter, this project pursues three objectives: the design of new materials that either enhance or decrease tunneling; the introduction of students on this project to a style of science that requires integration of skills from organic synthesis and materials science to quantum physics, and strengthening the U.S. technical workforce; the design, construction, and demonstration of new tools for studying tunneling that are broadly useful, and sufficiently simple for use at the undergraduate college level in science teaching. The objective of this project is to understand charge tunneling through thin, insulating organic films. It will use a junction developed specifically for this purpose that has three parts: i) an electrode of flat gold or silver; ii) a self-assembled monolayer (SAM) of an organic or organometallic compound (or mixture of compounds as the tunneling barrier; iii) a second electrode comprising a compliant structure composed of a drop of liquid eutectic gallium-indium alloy, covered with a thin, conducting film of gallium oxide. The project will measure the tunneling current across this junction at low voltages (V ~ 0.5V), using a number of SAMs designed to test theories relating to rates of tunneling, to the molecular and electronic structure of the molecules across which tunneling is occurring. The project will have two objectives: i) to validate a level of theory adequate to explain tunneling rates; ii) to use this theory to predict new types of tunneling mechanisms, and new phenomena involving tunneling, through organic matter. The desired outcome of the work is a fundamental understanding of the orbital structures particularly the highest energy occupied molecular orbitals, or HOMOs and the electronic couplings between them, that lead to either particularly high or particularly low charge tunneling rates. Both outcomes would be interesting, and both, ultimately, may be useful in the design of molecular electronic and organic electronic devices.