Research Activities:
Our research is focused on high-resolution local structure measurements on model systems for heterogeneous catalysis.

A detailed understanding of surface defects and adsorbates is highly desirable not least because of the suggested role as active sites in catalysis. Consequently we investigate localised electronic defects and ad-species on the surface. Most models are well defined metal supported oxide film systems or bulk crystal surfaces. The manifold of sites with different structures and various charge states often leads to highly convoluted signals in most averaging spectroscopy methods. Such results are difficult to disentangle. To gain both morphological and spectroscopic information on unit cell structure, defects, adsorption sites and ad-species at the atomic level, we employ local microscopic and spectroscopic characterization.

Our principal tool is frequency modulation dynamic force microscopy (FM-DFM), also known as non-contact atomic force microscopy (NC-AFM). We apply it in combination with scanning tunneling microscopy (STM). Both techniques are incorporated into a dual-mode FM-DFM/STM sensor operated in ultrahigh vacuum at low temperature (5 K).

This scientific approach opens up the way to analyse the local morphological nature of defects and adsorbates on thin oxide films as well as on thick films or bulk crystals. The charge state and the position of these defects and ad-species can be locally characterized as well as manipulated by interactions with the probing tip with high sensitivity and control. Our special dual-mode setup is capable of direct measurement and manipulation of local electronic properties and forces at the atomic level. The main goal for future experiments is to capture the dynamics of atomic scale processes.