1. Fachbereich Physik, CHyN, Universität Hamburg, 22761 Hamburg, Germany
2. Biosystems Technology, Institute of Life Sciences and Biomedical Technologies, Technical University of Applied Sciences Wildau, 15745 Wildau, Germany
3. Institut Català de Nanociència i Nanotecnologia (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Catalonia, Spain
4. Vall d'Hebron Institut de Recerca (VHIR), 08035 Barcelona, Catalonia, Spain
5. ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Catalonia, Spain
6. Department of Microelectronics, Nankai University, 30071 Tianjin, China