1. Centre for Innovation Competence SiLi-nano; Martin-Luther-University Halle-Wittenberg; Karl-Freiherr-von-Fritsch-Str. 3 06120 Halle (Saale) Germany
2. Nanoscience Laboratory; Department of Physics; University of Trento; via Sommarive 14 38123 Povo Trento Italy
3. NEST; Istituto Nanoscienze-CNR and Scuola Normale Superiore; P.za S, Silvestro 12 56127 Pisa Italy
4. Department of Advanced Photonics and Photovoltaics; Centre of Materials and Microsystems; Bruno Kessler Foundation; via Sommarive 18 38123 Povo Trento Italy
5. Institute of Physics; Martin-Luther-University Halle-Wittenberg; Heinrich-Damerow-Str. 4 06120 Halle (Saale) Germany
6. Max Planck Institute of Microstructure Physics; Weinberg 2 06120 Halle (Saale) Germany
7. Institut für Angewandte Physik; TU Bergakademie Freiberg; Leipziger Str. 23 09599 Freiberg Germany