1. Andrew and Erna Viterbi Faculty of Electrical Engineering, Technion, Haifa 32000, Israel
2. Russell Berrie Nanotechnology Institute, Technion, Haifa 32000, Israel
3. Technische Physik, Institute of Nanostructure Technologies and Analytics, Center of Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany