1. Institute of Materials Science of Barcelona (ICMAB-CSIC); Campus of the UAB; Bellaterra 08193 Spain
2. Department of Applied Physics; Feman Group; University of Barcelona; 08028 Barcelona Spain
3. Institute of Nanoscience and Nanotechnology (IN2UB); 08028 Barcelona Spain
4. Science and Technology Faculty; University of Twente; 7522 NB Enschede The Netherlands