Mechanismus of vibrational assisted electronic transport through single paraphenyl molecules investigated by electron and light sprectroscopy

本项目旨在通过低温扫描隧道显微镜（STM）尖端接近接触单分子，研究铅分子-铅结形成的步骤，将单分子隧道光谱研究与电子在单分子结中的传递研究结合起来。我们将研究氨基、吡啶和腈分子端基与氧官能化的铜表面和硅表面的原子悬垂键之间的孤对电子之间形成的稳定的分子电极接触。我们研究i)隧道状态，使用隧道光谱（弹性和非弹性）来揭示结构，电子组态和声子结构；ii)高电导状态，跟踪向接触的转变和分子共振向导电带的演变；iii)接触状态，确定传输机制（弹性与非弹性，相干与顺序）及其与分子和接触结构的关系。目标是提供表征良好的系统的可重复输运（电导-电压）特性，然后可以与SPP 1243的理论合作伙伴合作分析，以回答以下问题：引线电子配置在电荷输运中的作用是什么？分子轨道是如何从局部共振和振动演变成输运带和声子的？我们能在分子连接处看到电子封锁效应吗？能量是如何在分子中耗散的？

This project aims at bridging the research on single molecule tunnelling spectroscopy with research on electron transport through single-molecule junctions by using a low temperature scanning tunnelling microscope (STM) tip to approach to contact a single molecule, investigating the steps leading to the formation of a leadmolecule- lead junction. We will investigate stable molecule-electrode contacts formed by dative bonds between lone-pair electrons of amino, pyridine and nitrile molecular end-groups with oxygen functionalised copper surfaces and with atomic dangling bonds of silicon surfaces. We study i) the tunnel regime, using tunnel spectroscopy (elastic and inelastic) to reveal structure, electronic configuration and phonon structure, ii) the high conductance regime, to follow the transition to contact and the evolution of molecular resonances toward conducting bands, and iii) the contact regime, to identify transport mechanisms (elastic vs. inelastic, coherent vs. sequential) and their relation with molecular and contact structure. The goal is to provide reproducible transport (conductance-voltage) characteristics of well characterised systems, which can be then analysed in collaboration with theoretical partners in the SPP 1243 to answer the following questions: Which is the role of the leads electronic configuration in the charge transport? How do molecular orbitals evolve from local resonances and vibrations to transport bands and phonons? Can we see an electronic blockade effect in molecular junctions? How is energy dissipated in the molecule?