1. Transport at Nanoscale Interfaces Laboratory, Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
2. Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
3. Institute of Electronic, Microelectronic and Nanotechnology (IEMN), Centre National de la Recherche Scientifique, Villeneuve d’Ascq 59652, France
4. Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland