1. Experimentalphysik 2, Universität Augsburg, D-86159 Augsburg, Germany
2. SPEC, CEA, CNRS, Université Paris-Saclay, 91191 Gif sur Yvette, France
3. Physics and Materials Science Research Unit, University of Luxembourg, L-4422 Belvaux, Luxembourg
4. Department of Materials Research and Technology, Luxembourg Institute of Science and Technology, 41 Rue du Brill, L-4422 Belvaux, Luxembourg