1. Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece
2. Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
3. School of Science and Technology, Nottingham Trent University, Nottingham NG11 8NS, U.K.
4. Laboratoire des Technologies de la Microélectronique, University Grenoble Alpes, CNRS, CEA/LETI Minatec, F-38054 Grenoble Cedex, France
5. HORIBA Scientific, Avenue de la Vauve, Passage Jobin Yvon, 91120 Palaiseau, France
6. Department of Materials Science and Engineering, University of Ioannina, GR-45110 Ioannina, Greece