1. Zentrum für Innovationskompetenz SiLi-nano, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle, Germany.
2. Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle, Germany.
3. Leibniz Institute of Surface Engineering (IOM), 04318 Leipzig, Germany.
4. Laboratory of Infrared Materials and Devices, The Research Institute of Advanced Technologies, Ningbo University, 315211 Ningbo, China.