1. Angewandte Physik Sensorik, Brandenburgische TU Cottbus, K.-Wachsmann-Allee 17, 03046 Cottbus, Germany
2. Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
3. Department of Materials Science, Faculty of Sciences and Technology, New University of Lisbon and CEMOP-UNINOVA, Campus de Caparica, 2829-516 Caparica, Portugal