1. Physics and Chemistry Department, Technical University of Cluj-Napoca, 28 Memorandumului Str., 400114 Cluj-Napoca, Romania
2. Electron Microscopy Center, Faculty of Biology and Geology, Babes-Bolyai University of Cluj-Napoca, 1 M. Kogalniceanu Street, 400347 Cluj-Napoca, Romania
3. Materials Science and Engineering Department, Technical University of Cluj-Napoca, 103-105 Muncii Avenue, 400641 Cluj-Napoca, Romania