1. Institute of Micro‐ and Nanoelectronic Systems, University of Karlsruhe, Hertzstrasse 16, 76187 Karlsruhe, Germany
2. DLR Institute of Planetary Research, Rutherfordstrasse 2, 12489 Berlin, Germany
3. Physics‐Institute of the University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland