1. Solid Surface Analysis, Institute of Physics, Chemnitz University of Technology, Reichenhainer Str. 70, 09126 Chemnitz, Germany
2. Functional Magnetic Materials, Institute of Physics, Chemnitz University of Technology, Reichenhainer Str. 70, 09126 Chemnitz, Germany
3. Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
4. Semiconductor Physics, Institute of Physics, Chemnitz University of Technology, Reichenhainer Str. 70, 09126 Chemnitz, Germany
5. Department of Applied Physics, Hebrew University of Jerusalem, 91905 Jerusalem, Israel
6. Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, 91905 Jerusalem, Israel
7. Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warszawa, Poland