1. Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
2. Moscow Institute of Physics and Technology, Institutskiy Pereulok 9, Dolgoprudny, Moscow Region 141700, Russia
3. Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47057 Duisburg, Germany
4. Department of Applied Physics, Aalto University, Aalto, 00076 Espoo, Finland