Institute for Condensed Matter Physics, Technische Universitat Carolo-Wilhelmina, Braunschweig, Germany 38106 International Graduate School of Metrology, Technische Universiat Carolo-Wilhelmina, Braunschweig, Germany 38106
Institut ftir Anorganische und Analytische Chemie, Technische Universitat Carolo-Wilhelmina, Braunschweig, Germany 38106
Konrad-Zuse-Zentrum fur Informationstechnik, Berlin, Germany 14195
Institute of Energy Research and Physical Technologies, Technische Universitat Clausthal, Clausthal-Zellerfeld, Germany 38678
International Graduate School of Metrology, Technische Universiat Carolo-Wilhelmina, Braunschweig, Germany 38106 Institute of Electrical Measurement and Fundamental Electrical Engineering, Technische Universitiit Carolo-Wilhelmina, Braunschweig, Germany 38106