1. Zentrum für Innovationskompetenz SiLi-nano, Martin Luther Universität Halle-Wittenberg, Halle (Saale) 06120, Germany
2. Institute of Physics, Martin Luther Universität Halle-Wittenberg, Halle (Saale) 06120, Germany
3. School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005, India
4. Institut de Ciencia de Materials de Barcelona-CSIC, Campus de la UAB, Bellaterra, Barcelona 08193, Spain
5. Institute of Theoretical Physics, TU Bergakademie Freiberg, Freiberg D-09596, Germany
6. Leibniz Institute of Surface Engineering, Leipzig 04318, Germany
7. Laboratory of Infrared Materials and Devices, The Research Institute of Advanced Technologies, Ningbo University, Ningbo 315211, China