Pfnür Group, Leibniz Universität Hannover
This group is working on many different aspects of the physics at surfaces and interfaces. They comprise quantitative studies of structures and phase transitions at surfaces of single crystals and of two-dimensional adsorbate layers at submonolayer concentrations, selforganized growth of epitaxial layers and wires fabricated out of various combinations of semiconductors, metals and insulators, and, most recently, the fabrication and characterization of ultra-small structures including the development of new structuring techniques (electron beam lithography in UHV in combination with STM and electromigration). These are generated in order to characterize the electronic transport in these ultra-small and ultra-thin structures. For many aspects of these projects an intense collaboration with collegues for chemistry and electrical engineering was established over the last years.
Emphasis in our work is put on the physical characterization of properties on the atomic scale, which requires to a large extent to carry out experiments in UHV, and to couple them with quantitative calculcations. This approach turns out to be increasingly important for an understanding and the control of physical properties in structures with dimensions in the range of a few nanometers. For our experiments electron spectroscopies (XPS, UPS) are available as well as electron loss spectroscopy with simultaneous high energy and momentum resolution. In addition we use for geometrical and spectroscopic characterization electron diffraction LEED), tunneling and scanning probe microscopies. For structuring e-beam lithography is available. New structuring methodes are tested in a combination of UHV-SEM and STM. In addition we carry out magnetotransport measurements in UHV.