1. Institute of Materials Science of Barcelona, ICMAB-CSIC, Campus UAB, 08193 Bellaterra, Spain
2. Applied Physics Department, Barcelona University, Martí i Franquès, 1, 08028 Barcelona, Spain
3. ENPHOCAMAT Group, Institute of Nanoscience and Nanotechnology of University of Barcelona (IN2UB), Martí i Franquès, 1, 08028 Barcelona, Spain
4. National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 36, 77125 Bucharest, Romania
5. National Institute for Materials Physics, P.O.
Box MG 7, 77125 Bucharest, Romania