1. Walter Schottky Institut and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
2. Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
3. nanotech@surfaces Laboratory, Empa − Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
4. Institute of Physics, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str.10, 48149 Münster, Germany
5. Munich Center for Quantum Science and Technology (MCQST), Schellingstrasse 4, 80799 München, Germany