Atomic structure and electronic properties of interfaces formed by perovskite and organic charge transfer materials

钙钛矿是一组氧化物半导体，作为基于氧化物的设备的衬底有着悠久的历史。钛酸锶(SrTiO_3)是钙钛矿型半导体材料中的一种。酞菁是一种有机半导体，它是完全共轭的平面芳香族分子，也可用作模型体系。除了过渡金属酞菁络合物外，周边取代的酞菁类化合物也是当前表面科学研究的热点。不同的酞菁材料的组合，一方面由电子受体组成，另一方面由电子供体组成，表明带隙中有新的电子态。如果能够有意识地控制有机电荷转移材料与钙钛矿表面之间的相互作用，这种结构可以用于新型的(光电)电子器件。本文拟对钙钛矿与有机电荷转移材料形成界面的研究开辟了一个新的研究领域。这里的中心问题将是是否可以组装新的半导体表面/界面，其中两种组成材料中的任何一种的修改都会在界面的半导体侧产生电或光激活的开关效应，如果是这样的话，在什么条件下。本项目的总体目标是利用扫描隧道显微镜/电子能谱(STM/STS)研究钙钛矿与有机电荷转移材料形成的界面的原子结构和电子性质。STM/STS是在原子尺度上研究氧化物和有机半导体电子性质的一种成功工具。因此，我们将研究形成在钙钛矿表面和这些表面上的有机电荷转移材料薄膜中的电子态的空间和能量局域化。此外，对于表面和界面的结构特征，还将使用其他方法，如原子力显微镜、低能电子衍射和俄歇电子能谱。目标是收集关于钙钛矿-有机电荷转移材料界面的基本信息。

Perovskites are a group of oxide semiconductors, having a long history as substrates for oxide-based devices. Strontiumtitanate (SrTiO3) is one model semiconductors for the perovskite family. Phthalocyanines are organic semiconductors, which are fully conjugated, planar aromatic molecules, and also used as model system. Beside the transition metal phthalocyanine complexes also the peripherally substituted phthalocyanines are in the focus of current surface science studies. Combinations of different phthalocyanine materials, consisting of on the one hand an electron acceptor, and on the other hand an electron donor, indicate new electronic states in the band gap. Such structures maybe used for novel (opto)- electronic devices, if the interaction between the organic charge transfer material and the perovskite surface can be intentionally controlled. The here planned research about the formation of interfaces formed by perovskites and organic charge transfer materials opens up a new research field. The central question here will be whether new semiconducting surfaces/interfaces can be assembled, in which a modification of either one of the two constituent materials leads to electrically or optically activated switching effects at the semiconductor side of the interface, and if so under which conditions. The overall objective of this project is to investigate the atomic structure and electronic properties of interfaces formed by perovskite and organic charge transfer materials by means of scanning tunneling microscopy/-spectroscopy (STM/STS). STM/STS is a successful tool to study the electronic properties of oxidic as well as organic semiconductors at the atomic scale. Hence, the spatial and energetic localization of the electronic states formed at surfaces of perovskites and within thin films of organic charge transfer materials on these surfaces will be studied. Furthermore, for the structural chacterization of the surfaces and interfaces other methods like atomic force microscopy, low-energy electron diffraction and Auger electron spectroscopy will be performed. The goal is to gather fundamental information about the perovskite-organic charge transfer material interface.