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. Indian Institute of Technology, Banaras Hindu University, Varanasi 221005, India
4. Leibniz Institute of Surface Engineering, Leipzig 04318, Germany
5. Laboratory of Infrared Materials and Devices, The Research Institute of Advanced Technologies, Ningbo University, Ningbo 315211, China
6. Institute of Theoretical Physics, TU Bergakademie Freiberg, Freiberg D-09596, Germany