1. Applied Physics Laboratory, Faculty of Sciences of Sfax, University of Sfax, 3000 Sfax, Tunisia
2. Physics Department, CFisUC, University of Coimbra, Rua Larga, P-3004-516 Coimbra, Portugal
3. I3N, Physics Department, University of Aveiro, Campus de Santiago, Aveiro, Portugal
4. Material Physics Laboratory and Environnement-Applied Nanomaterials, Faculty of Sciences of Gabes, University of Gabes, 6079 Gabes, Tunisia