Resonant Photoemission on Organic Thin Films and Interfaces

有机材料的独特物理性质受到单个分子与其局部环境的耦合的关键影响。特别地，确定例如宏观输运特性或光学性质的动态过程受到复杂的相互作用机制的影响。最终，对这些机制的微观理解是对系统特性进行特定控制的基础。与完全长程有序的固体相反，在凝聚有机体系中，相应的机制可以不太清楚地区分，因此需要昂贵的制备和分析方法。本计画将利用共振光电子能谱（ResPES）系统地研究有机半导体薄膜的电子结构。该方法是基于一个核心电子的本地激发.诱导的许多粒子的过程，这通常是很好的理解，从理论的观点，承载的特征光谱信息，这允许的结论的电子或分子系统的动力学性质，分别.这些许多粒子过程发生在比初级激发小得多的能量尺度上，并且可以包含例如芯孔的局部屏蔽、分子间电荷转移或集体电子振动或电子激发。在这个项目中，我们将具体调查： 在弱结合的情况下，ResPES-光谱对分子上的外部影响的灵敏度：ResPES-光谱显示特征精细结构，这可以归因于激发的中间态与分子振动的耦合。如果在不同的环境中检查分子，即使化学键很弱，这种振动特征也会显示出差异。- 电荷转移过程的时间序列通过“芯-孔时钟”方法：电子激发后的电荷转移将在薄分子膜中，在分子/金属界面，并在异质界面（分子A/分子B）进行研究。该项目旨在系统研究特定有机分子与周围环境的物理耦合及其对振动和电子激发的影响。这将提高对有机分子材料的微观理解。

The unique physical properties of organic materials are crucially influenced by the coupling of the single molecule to its local surrounding. In particular, dynamic processes, which determine e.g. the macroscopic transport characteristics or the optical properties, are influenced by complex interaction mechanisms. Ultimately, a microscopic understanding of these mechanisms is the basis for a specific control of the system properties. In contrast to perfectly long-range ordered solids, the respective mechanisms can be less clearly distinguished in condensed organic systems, thus requiring expensive preparation and analysis methods. In this project resonant Photoelectron Spectroscopy (ResPES) will be applied for the systematic investigation of the electronic structure of organic semiconductor films. The method is based on the local excitation of a core electron. The induced many particle processes, which are generally well understood from a theoretical viewpoint, bear characteristic spectral information, which allow conclusions on the dynamic properties of the electronic or molecular system, respectively. These many particle processes occur on a much smaller energy scale than the primary excitation and can contain e.g. a local screening of the core hole, intermolecular charge transfer, or collective vibronic or electronic excitations. In this project we will specifically investigate: - The sensitivity of the ResPES-spectra for external influences on molecules in case of weak binding: ResPES-spectra show characteristic fine structures, which can be attributed to the coupling of the excited intermediate state to molecular vibrations. This vibronic signature shows differences if the molecules are examined in different surrounding, even if the chemical bonding is weak. - The temporal sequence of charge transfer processes via the ‘core-hole clock ‘-method: the charge transfer following the electronic excitation will be investigated in thin molecular films, at molecule/metal-interfaces, and at heterointerfaces (molecule A/molecule B). This project aims on the systematic investigation of the physical coupling of particular organic molecules to the surrounding and its effect on vibronic and electronic excitations. It will improve the microscopic understanding of organic molecular materials.