1. Solid State Physics Division, Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Linz, Austria
2. Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Dresden, Germany
3. Max Planck Institute for Intelligent Systems, Stuttgart, Germany
4. Paul Scherrer Institute, Villigen, Switzerland
5. Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany