1. Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4A, DK-9220 Aalborg Øst, Denmark
2. Institute of Sensors, Signals and Electrotechnics (SENSE), University of Southern Denmark, Niels Bohrs Allé 1, DK-5230 Odense M, Denmark
3. ISIS, CNRS UMR 7006, Université Louis Pasteur, 8 allée Monge, BP 70028, 67083 Strasbourg, France