Collaborative Research: Probing and Controlling Binding Structure and Electron Transport in Molecular Electronic Devices - A Coordinated Computational and Experimental Study

摘要：非技术：分子电子学最初的想法是将单个分子连接到两个金属电极上，称为单分子结，作为商业微电子器件中单个电子元件的类比，以克服著名的摩尔预测的限制。在单个分子结中，影响电子传递特性的最难以捉摸的因素可能在于分子-电极接触界面。尽管不断取得实验成果和分子电子器件的概念简单，但他们对电子传递和分子结合结构之间关系的理论理解仍然存在挑战。因此，探测和控制单分子连接的结构和动力学，从而控制这些连接的分子运输对该领域的发展至关重要。该项目将整合自组装和表面和界面纳米接触动力学的分子模拟，以及单分子结的实验力学和电子传递测量。该项目将提供对在分子力和电导测量中观察到的许多过渡现象的深刻理解。如果研究成功，将对分子电子学以及能量研究、分子力谱学等诸多领域产生巨大影响。本提案的教育和推广目标是将研究工作和成果与研究生，本科和K-12教育紧密结合，并在全球传播研究和教育成果。技术方面：虽然单分子结的电导率和机械性能在过去十年中取得了重大进展，但对分子结合结构和电子传递的详细理解以及结构-力-电导率相关性的挑战仍然没有解决。本研究将发展分子模拟与扫描探针显微镜断结相结合的技术来探测和控制分子电子器件的结构和动力学：(1)通过尽可能接近实验参数、电极动力学和真实原子相互作用进行分子模拟，了解扫描探针实验中的结合结构和力测量；(2)开发了一种射频交流耦合高速放大器双模反馈系统，以捕获诱导电导变化的分子结合位点的关键转变。在纳秒（ns）时间尺度下的实验数据将直接与分子模拟结果进行比较；(3)采用协同分子模拟和扫描探针断结实验对所选基准系统在不同模式训练下的结构和动力学特性进行了研究。将在实验和模拟中对力和电导轨迹进行多变量力-电导二维互相关直方图分析，并识别分子结的不同稳定构型。计算与实验的协同研究项目也将为材料、力学、化学、电子和计算材料科学的学生提供跨学科的研究。

Abstract:Non-Technical:Molecular electronics started with the idea of wiring an individual molecule to two metal electrodes, called single-molecule junctions, as an analogy of single electronic components in commercial microelectronic devices to overcome the limit of famous Moore's prediction. In a single molecular junction, perhaps the most elusive factor that influences the electron transport properties lies in the molecule-electrode contact interfaces. Despite continuous experimental achievements and the conceptual simplicity of molecular electronic devices, challenges for their theoretical understanding of the correlation between electron transport and molecular binding structures are still unresolved. Therefore, probing and controlling the structure and dynamics of single-molecule junctions and consequently controlling the molecular transport of these junctions are critical to the development of this field. The project will integrate molecular simulations for the self-assembly and nanocontact dynamics at surface and interface, and experimental mechanics and electron transport measurements of single-molecule junctions. The project will provide a deep understanding of many transition phenomena observed in molecular force and conductance measurements. If successful, the research will have tremendous impact on molecular electronics community and many other areas, such as energy research and molecular force spectroscopy. The education and outreach objective of this proposal is to tightly integrate the research efforts and results with graduate, undergraduate, and K-12 education and to globally disseminate both research and the education outcomes.Technical:Although the electrical conductance and mechanical properties of single-molecule junctions have achieved significant progress over the past decade, challenges of a detailed understanding of molecular binding structures and electron transport, and the structure-force-conductance correlations, are still unresolved. This research will develop a combined molecular simulation and scanning probe microscope break-junction technique to probe and control the structure and dynamics in molecular electronics devices: (1) Performing molecular simulations by using as close as possible the experimental parameters, dynamics of electrode and realistic atomic interactions to understand the binding structure and force measurement in scanning probe experiment; (2) Developing a dual-mode feedback system with AC-coupled high speed amplifier at radio frequency to capture the key transitions of molecular binding sites that induce conductance changes. The experimental data at nanosecond (ns) timescale will be directly compared with molecular simulation results; (3) Using the coordinated molecular simulation and scanning probe break-junction experiment to probe the structure and dynamics of selected benchmark systems under different mode trainings. Multi-variable force-conductance two-dimensional cross-correlation histogram analyses for the force and conductance traces will be performed in experiments and simulations, and the distinct stable configurations of molecular junctions will be identified. The coordinated computational and experimental research project will also provide an interdisciplinary research for students in materials, mechanics, chemistry, electronics, and computational materials science.