1. Department of Informatics and Microsystem Technology, University of Applied Sciences Kaiserslautern, Amerikastrasse 1, 66482 Zweibrücken, Germany
2. INESC Microsistemas e Nanotecnologias, Rua Alves Redol, 91000-029 Lisbon, Portugal
3. Department of Electronic and Electrical Engineering, University of Bath, BA2 7AY Bath, United Kingdom
4. Institute of Physics I, RWTH Aachen University, Sommerfeldstr. 14, 52074 Aachen, Germany