Single-Electron Alternate-Charging Scanning Tunneling Microscopy on Insulating Surfaces

绝缘表面上的单电子交替充电扫描隧道显微镜

• 批准号: 391277787
• 负责人: Professor Dr. Jascha Repp
• 金额: --
• 依托单位: Institut für Experimentelle und Angewandte Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/391277787?language=en
• 关键词: Single; Electron; Alternate; Charging; Scanning

Understanding the electronic structure of matter on the atomic scale is one of the central goals of nanoscience. In particular, many chemical processes are governed by the exchange of electrons between atoms and molecules, a mechanism known as electron transfer. Probing such phenomena requires the capability to study atom and molecules at their own length scales, while at the same time being able to control their charge states.While Scanning Tunneling Microscopy (STM) allows imaging electronic states with Angstrom resolution, the requirement of a conductive substrate hinders the investigation of completely electronically isolated adsorbate structures in given charge states. Recently, combining elements of STM and AFM, we successfully developed a novel imaging and spectroscopy method, referred to as single-electron Alternate-Charging Scanning Tunneling Microscopy (AC-STM), in the framework of a running project. Here, in our renewal proposal, we aim at applying this novel method to various physical questions that, without the AC-STM technique, have been elusive. In fact, by enabling electronic state imaging on insulators, with this method one can also study higher lying excited states, in particular multiply-ionized molecules. We make use of these possibilities in five different contexts. First, we aim to study the electron-electron repulsion within single oligomeric molecules, as model systems for conducting polymers. Second, we would like to use AC-STM to identify reaction products, formed by charge injection. The need to access multiple charge states in these single-molecule reactions inhibits conventional STM characterization, highlighting the possibilities brought about by AC-STM. Third, we wish to expand the technique to its full spectroscopic capabilities, such that it can provide not only the energy of different charge state transitions, but also level broadening, polaronic shifts and maybe even vibrational excitations. Fourth, we would like to explore the possibilities to also access non-equilibrium states within each charge state. For example, by a suitable sequential injection of different charge carriers, it should be possible to prepare a molecule with a HOMO-LUMO excitation (exciton), providing access to the energetics of charge conserving optical transitions with electron-transfer reactions. Finally, we propose to combine AC-STM with luminescence experiments on thick insulators. This project will open up a new arena of single-molecule experiments with access to the entire class of phenomena involving out-of-equilibrium charge states.

了解原子尺度上物质的电子结构是纳米科学的核心目标之一。特别是，许多化学过程是由原子和分子之间的电子交换控制的，这种机制称为电子转移。探测这种现象需要研究原子和分子在它们自己的长度尺度上的能力，同时能够控制它们的电荷状态。虽然扫描隧道显微镜（STM）允许以埃分辨率成像电子状态，但导电基底的要求阻碍了在给定电荷状态下完全电子隔离的吸附物结构的研究。最近，结合STM和AFM的元素，我们成功地开发了一种新的成像和光谱方法，称为单电子交替充电扫描隧道显微镜（AC-STM），在一个正在运行的项目的框架。在这里，在我们的更新建议中，我们的目标是将这种新方法应用于各种物理问题，如果没有AC-STM技术，这些问题一直是难以捉摸的。事实上，通过在绝缘体上实现电子态成像，用这种方法也可以研究更高的激发态，特别是多重电离分子。我们在五种不同的情况下利用这些可能性。首先，我们的目标是研究单个低聚分子内的电子-电子排斥，作为导电聚合物的模型系统。其次，我们希望使用AC-STM来识别电荷注入形成的反应产物。在这些单分子反应中需要访问多个电荷状态抑制了传统的STM表征，突出了AC-STM带来的可能性。第三，我们希望将该技术扩展到其全部光谱能力，这样它不仅可以提供不同电荷态跃迁的能量，还可以提供能级展宽，极化子位移甚至振动激发。第四，我们想探索在每个电荷状态中也进入非平衡态的可能性。例如，通过合适的顺序注入不同的电荷载流子，应该可以制备具有HOMO-LUMO激发（激子）的分子，从而提供对具有电子转移反应的电荷守恒光学跃迁的能量学的访问。最后，我们建议将联合收割机AC-STM与厚绝缘体上的发光实验相结合。这个项目将开辟一个新的竞技场的单分子实验与访问的整个类的现象，涉及出平衡电荷状态。