1. Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, 1015 Lausanne, Switzerland
2. Empa, Swiss Federal Laboratories for Materials Science and Technology, nanotech@surfaces Laboratory, Feuerwerkerstrasse 39, 3602 Thun, Switzerland
3. Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
4. Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland