1. Laboratory for Solid State Physics; ETH Zürich; Otto-Stern-Weg 1 CH- 8093 Zürich Switzerland
2. L-NESS and Department of Materials Science; Università di Milano-Bicocca; Via Cozzi 55 I- 20125 Milano Italy
3. Electron Microscopy Center EMPA; Swiss Federal Laboratories for Materials; Science and Technology; Überlandstrasse 129 CH -8600 Dübendorf Switzerland
4. Department of Condensed Matter Physics; Masaryk University; Kotlárˇská 2 61137 Brno Czech Republic
5. CEITEC; Masaryk University; Kamenice 5 60177 Brno Czech Republic
6. L-NESS and Department of Physics; Politecnico di Milano; Via Anzani 42 I-22100 Como Italy
7. CSEM; Rue Jaquet-Droz 1 CH -2002 Neuchâtel Switzerland