1. Institute for Integrative Nanosciences, IFW-Dresden, Helmholtz Strasse 20, 01069 Dresden, Germany
2. Max Planck Institute for Solid State Research, Heisenberg Strasse 1, 70569 Stuttgart, Germany
3. Material Systems for Nanoelectronics, TU-Chemnitz, Reichenhainer Strasse 70, 09107 Chemnitz, Germany