1. Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE); University of Duisburg-Essen; 47048 Duisburg Germany
2. Institute of Materials Science; Technische Universität Darmstadt; 64287 Darmstadt Germany
3. Institut de Ciència de Materials de Barcelona (ICMAB-CSIC); Campus UAB 08193 Bellaterra Spain
4. Institute for Materials Science and Center for Nanointegration Duisburg-Essen (CENIDE); University of Duisburg-Essen; 45141 Essen Germany
5. Materials Theory; ETH Zürich; Wolfgang-Pauli-Str. 27 8093 Zürich Switzerland