1. Semiconductor Physics, Chemnitz University of Technology, 09107 Chemnitz, Germany
2. L.V. Pysarzhevsky Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 03028 Kyiv, Ukraine
3. Division Biophotonics, Federal Institute for Materials Research and Testing (BAM), 12489 Berlin, Germany
4. Physical Chemistry, Technical University of Dresden, 01062 Dresden, Germany