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

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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.