1. Ernst Ruska-Centre
for Microscopy and Spectroscopy with Electrons, Forschungszentrum
Jülich GmbH, Jülich 52425, Germany
2. Central
Facility for Electron Microscopy (GFE), RWTH Aachen University, Aachen 52074, Germany
3. Institute
of Inorganic Chemistry, University of Bonn, Bonn 523117, Germany
4. Peter Grünberg
Institute, Forschungszentrum Jülich GmbH, Jülich 52425, Germany