1. Faculty of Physics, Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany
2. Department of Metallurgical and Materials Engineering, Muğla Sıtkı Koçman University, 48000 Mugla, Turkey
3. Functional Materials, Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt, Germany