The chair of Physical Chemistry II has been started 1966 by Prof. Dr. G. Wedler. Prof. Dr. H.-P. Steinrück was elected as his successor 1988.

Further biographical information

The research activities of our group focus on the area of surface and interface science. The main research topics are:

• New materials with novel electronic, geometric and chemical properties

• Elementary steps of surface reactions

• Development and construction of scientific apparatus
  

For our investigations a large variety of experimental methods is applied, including synchrotron radiation-based techniques. In particular, the following topics are investigated:

Growth, characterization and modification of ultrathin layers:
The goal is the detailed investigation of the growth modes of various layer systems and surface alloys. We are particularly interested to find the optimum conditions for two- or three-dimensional growth - depending on the desired application. In addition, we search for possibilities to influence the growth mode in a well defined way by choosing the appropriate growth conditions or other parameters such as e.g. the interface composition or coadsorbed molecules. The investigated substrates range from ultrathin metal and oxide layers on metals and oxides, to silicides, metal/molecule sandwich layers and organic layers on metals.

Lateral Nanostructures:
Here we extend our investigations on layer systems (which represent vertical nanostructures) to well-defined lateral nanostructures and laterally nanostructured surfaces. The investigated length scales range from the subnanometer region (i.e. atomic resolution) up to structured areas of some mm. Central topics are the preparation of nanostructures on surfaces and the investigation of the related chemical properties; special attention is paid to new preparation routes and new nanoscopic materials relevant for heterogeneous catalysis. At the moment we are installing a new, combined scanning electron and scanning tunneling microscope, which allows to study the same spot on the surface with both methods.

Gas-surface interaction and surface reactions:
In this area we want to obtain a detailed understanding of the elementary steps of heterogeneous catalysis based on studies of various model reactions. Important topics are the kinetics and dynamics of the adsorption process and their dependence on chemical nature, composition and structure of the surface, temperature, coverage, presence of coadsorbates, pressure or impingement rate and the translational and internal energy of the particles. Of particular interest are in situ studies of adsorption and reaction processes using X-ray photoelectron spectroscopy. Measurements at pressures up to 1 mbar allow to bridge the so-called „pressure gap“ and thereby to connect Surface Science and real catalysis at ambient pressures and high temperatures.

Electronic, geometric, chemical properties and adsorption:
The key for understanding of the surface and layer properties is the knowledge of their electronic and geometric structures. Based on that information, a central goal of our studies is the modification of the chemical properties of these systems, especially the bonding of various adsorbates to the surface and their reactivity, by the appropriate combination of different materials. The studies on the electronic properties focus on the k-resolved band structures of the substrate and/or the adsorbate layers which show, depending on the individual system, one-, two- or three-dimensional behavior. Concerning the geometric properties we are interested to determine the structure of the surface or the layer systems as well as the adsorption sites, orientation and bond distances of adsorbates. In addition, by high resolution X-ray photoelectron spectroscopy detailed the chemical identity and the nature of the chemical bond of adsorbates and intermediates can be derived. The majority of studies concentrates on small molecules, such as CO, NO, water, methane, ethane, ethene, benzene, an so on. Since recently, we also investigate the properties metalloporphyrins.

Technical developments:
In the last years we have built up two new unique photoelectron spectrometers. One is combined with a supersonic molecular beam and is designed for measurements with synchrotron radiation; it allows highly resolved XPS-measurements with a data collection time of down to 1 sec. The other is a lab apparatus developed to study surface reactions in the so-called “pressure gap”, i.e. up to pressures up to 1 mbar.

For our investigations we use a variety of experimental methods, partly utilizing synchrotron radiation at BESSY II, MAX-II, ELETTRA, ALS):

• High resolution X-ray photoelectron spectroscopy (XPS)

• Angle-resolved UV photoelectron spectroscopy (ARUPS)

• Auger electron spectroscopy (AES, XAES)

• Photoelectron diffraction (XPD)

• X-ray absorption spectroscopy (NEXAFS)

• Temperature programmed desorption (TPD)

• Work function measurements

• Scanning tunneling microscopy (STM)

• Scanning electron microscopy (SEM)

• Atomic force microscopy (AFM)

• Low energy ion scattering (LEIS)

• Low energy electron diffraction (LEED, including LEED-IV analysis)

• Molecular beam methods (Maxwell- and supersonic beams)

• Gas chromatography (GC)
  

• no research projects have been entered yet