1. Institute of Technology for Nanostructures (NST), Faculty of Engineering, University of Duisburg-Essen, Bismarckstr. 81, D-47057 Duisburg, Germany
2. Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, D-47048 Duisburg, Germany
3. Department of Solid State Electronics (HLT), Faculty of Engineering, University of Duisburg-Essen, Lotharstr. 55, D-47048 Duisburg, Germany
4. General and Theoretical Electrical Engineering (ATE), Faculty of Engineering, University of Duisburg-Essen, Bismarckstr. 81, D-47057 Duisburg, Germany