[1] Univ Duisburg Essen, Fak Phys, D-47057 Duisburg, Germany
[2] Univ Duisburg Essen, CeNIDE, D-47057 Duisburg, Germany
[3] Tech Univ Denmark, Ctr Electron Nanoscopy, DK-2800 Lyngby, Denmark
[4] European Synchrotron Radiat Facil, F-38043 Grenoble, France
[5] Res Ctr Julich, Peter Grunberg Inst, Ernst Ruska Ctr Microscopy & Spect Electrons, D-52425 Julich, Germany