1. Central Facility of Electron Microscopy, Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
2. Institute of Optoelectronics, Ulm University, Albert-Einstein-Allee 45, 89081 Ulm, Germany
3. Institute of Quantum Matter, Ulm University, Albert-Einstein-Allee 45, 89081 Ulm, Germany