1. Institute of Nanostructure- and Solid State Physics and Center for Hybrid Nanostructures; Universität Hamburg; Luruper Chaussee 149 22607 Hamburg Germany
2. Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden); Institute for Metallic Materials; Helmholtzstrasse 20 01069 Dresden Germany
3. Institute of Materials Science; Technical University Dreden; Helmholtzstrasse 10 01062 Dresden Germany