1. Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zurich, Switzerland
2. Department of Civil, Environmental and Geomatic Engineering, ETH Zürich, CH-8093 Zurich, Switzerland
3. Nanoscience and Materials Division, INRIM, Strada delle Cacce 91, Turin, Italy
4. Dipartimento Scienze and Innovazione Tecnologica, Università del Piemonte Orientale, 1512 Alessandria, Italy
5. Physics Department and NIS Interdepartmental Center, University of Torino, Via Pietro Giuria 1, 10125 Torino, Italy
6. Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland