1. nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf 8600, Switzerland
2. Center for Advancing Electronics Dresden & Faculty of Chemistry and Food Chemistry, TU Dresden, Dresden 01062, Germany
3. Laboratory of Nanostructures at Surfaces, Institute of Physics, École Polytechnique Fédérale de Lausanne, Lausanne 1015, Switzerland
4. Max Planck Institute of Microstructure Physics, Weinberg 2, Halle 06120, Germany
5. Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern 3012, Switzerland