1. Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
2. Institute of Applied Physics, KIT, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, Germany
3. Material Science and Solar Energy group, Department of Physics, University of Dar es Salaam (UDSM), P. O. Box 35063, Dar es Salaam, Tanzania
4. Laboratory for Electron Microscopy, KIT, Engesserstr. 7, 76131 Karlsruhe, Germany
5. Institute for Applied Materials, KIT, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
6. Light Technology Institute, KIT, Engesserstr. 13, 76131 Karlsruhe, Germany