1. Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 12489, Germany
2. Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin 14109, Germany
3. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
4. A.J. Drexel Nanomaterials Institute, Drexel University, Philadelphia, Pennsylvania 19104, United States
5. Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
6. Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 02792, Korea