Structure-reactivity relationship of defects on MgO

In the current project, the structure-reactivity relationship of defects on oxide surfaces will be examined on the atomic scale by a combined use of imaging and spectroscopic methods. Metal oxides play a crucial role in many technologically relevant processes. Especially in heterogeneous catalysis experimental findings may only partially described by simple models. For a complete understanding of the processes occurring at the interface between the surface of the solid and the environment, a detailed knowledge of the physical and chemical properties on the atomic scale is necessary. Magnesium oxide (MgO) is, due to its simple crystal structure, often chosen as a model substance for the investigation of physical and chemical processes on the surface. Defects on the MgO surface are important as reaction sites as well as nucleation centres for small metal clusters. However, corresponding experimental studies with indirect, non-imaging spectroscopic methods always exhibit a touch of speculation. The aim of the current project is to connect for the first time the structural information about defects on well- defined oxide surfaces with their spectroscopic properties on the atomic scale to provide a direct relation between structure and reactivity of the defects. For this purpose, few atomic layers thin MgO films are prepared on a single-crystalline metallic substrate. The defect-free as well as the defective surface of these films will be investigated by both imaging (Scanning Tunneling Microscopy, STM) and spectroscopic (Electron Spin Resonance, ESR) methods. The possibility of performing local spectroscopy with STM opens up the route for determining the electronic properties of single surface defects and adsorbates for the first time.