1. Department of Science
and Analysis of Materials (SAM), CRP − Gabriel Lippmann, L-4422 Belvaux, Luxembourg
2. Institut Jean Lamour (IJL) CNRS UMR 7198, Université de Lorraine, Faculté des Sciences et Technologies, BP 70239, F-54506 Vandoeuvre-les-Nancy
Cedex, France
3. Department
of Applied Physics, Aalto University School of Science, FI-00076 Aalto, Finland
4. Department of Physics, University of Helsinki, P.O.Box 43, FI-00014 Helsinki, Finland