1. Central Facility for Electron Microscopy, Ulm University, Albert Einstein Allee 11, 89081 Ulm, Germany
2. Institute for Inorganic Chemistry II, Ulm University, Albert Einstein Allee 11, 89081 Ulm Germany
3. Experimental Physics II, Institute of Physics, University of Augsburg, Universitätsstr. 1, 86159 Augsburg, Germany
4. Department of Physics, Tanta University, 31527 Tanta, Egypt