1. Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology, Winterbergstrasse 28, D-01277 Dresden, Germany
2. Institute of Solid State Electronics, Technische Universität Dresden, Mommsenstrasse 15, D-01069 Dresden, Germany
3. Synthesis and Real Structure, Department of Material Science, Kiel University, Kaiserstrasse 2, D-24143 Kiel, Germany
4. Kiel Nano, Surface and Interface Science, Kiel University, Christian-Albrechts-Platz 4, D-24118 Kiel, Germany
5. Department of Physics, Chemistry and Biology, Linköpings Universitet, SE-581 83 Linköping, Sweden
6. Fraunhofer Institute for Integrated Systems and Device Technology, Schottkystrasse 10, D-91058 Erlangen, Germany