1. Physical Chemistry I, Department of Chemistry and Center of Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 45141Essen, Germany
2. General and Theoretical Electrical Engineering (ATE), Faculty of Engineering, University of Duisburg-Essen, and Center for Nanointegration Duisburg-Essen (CENIDE), D-47048Duisburg, Germany
3. Institute of Electron Microscopy and Nanoanalysis, NAWI Graz, Graz University of Technology, Steyrergasse 17, 8010Graz, Austria