1. Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
2. Nanosurf Lab, Institute of Physics of the Czech Academy of Sciences, Cukrovarnicka 10, 162 00 Prague 6, Czech Republic
3. Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland