1. Faculty of Fundamental Problems of Technology Department of Experimental Physics Wrocław University of Science and Technology; St. Wyspiańskiego 27 50-370 Wrocław Poland
2. Technische Physik Institute of Nanostructure Technology and Analytics, CINSaT University of Kassel; Heinrich Plett-Str. 40 D-34132 Kassel Germany
3. Institute of Solid State Physics Universität Bremen; Otto-Hahn-Allee 1 28359 Bremen Germany