1. Institut für Physik & IRIS Adlershof Humboldt-Universität zu Berlin 12489 Berlin Germany
2. Helmholtz-Zentrum Berlin für Materialien und Energie GmbH 12489 Berlin Germany
3. Sara and Moshe Zisapel Nanoelectronics Center Andrew & Erna Viterbi Department of Electrical and Computer Engineering Technion Haifa 32000 Israel
4. Electrical Engineering and Computer Science Technical University Berlin 10587 Berlin Germany