1. Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Zürich, Wolfgang-Pauli-Strasse 10, 8093 Zürich, Switzerland, AO Research Institute, Clavadelerstrasse, 7270 Davos, Switzerland, Ciba Specialty Chemicals, Klybeckstrasse 141, 4002 Basel, Switzerland, SuSoS AG, Lagerstrasse 14, 8600 Dübendorf, Switzerland