1. Institute of Applied Physics, Justus Liebig University Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, Germany
2. Center of Materials Research (ZfM), Justus Liebig University Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, Germany
3. Institute of Physical Chemistry, Justus Liebig University Gießen, Heinrich-Buff-Ring 17, 35392 Gießen, Germany
4. Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy