1. II. Physikalisches Insitut, Universität zu Köln, Zülpicher
Straße 77, 50937 Köln, Germany
2. Department of Physics, University of Helsinki, P.O. Box 43, 00014 Helsinki,
Finland
3. Central Facility
for Electron
Microscopy, Group of Electron Microscopy of Materials Science, University of Ulm, 89081 Ulm, Germany
4. Department of Physics, University of Vienna, Boltzmanngasse 5, 1190 Wien,
Austria
5. Department of Applied
Physics, Aalto University, P.O. Box 11100,
00076 Aalto, Finland