[1] RWTH Aachen University, Nordrhein-Westfalen, Aachen, Germany
[2] Max Planck Institute of Microstructure Physics, Halle (Saale), Germany
[3] Leibniz Institute for High Performance Microelectronics, Brandenburg, Frankfurt (Oder), Germany
[4] Karlsruhe Institute of Technology, Baden-Württemberg, Karlsruhe, Germany