The investigation of some structural, optical and magnetic properties of Mn, Co and Ni-doped zinc oxysulfide films

In this study, we investigated the structural, optical and magnetic properties of Mn, Co and Ni-doped Zn(O,S) films. Undoped Zn(O,S) films were deposited by a spray pyrolysis method on glass substrate. Thin Mn, Co and Ni layers evaporated on these films served as the source for the diffusion doping. Doping was accomplished by annealing the stack layers at the temperature range from 300 °C to 450 °C in steps of 50 °C for 45 minutes under vacuum (2x10?5 Torr). The XRD pattern of undoped films revealed the presence of two wurtzite phases corresponding to ZnS and ZnO with a strong preferred orientation along the ZnS [002] direction. SEM showed a similar surface morphology for the undoped and doped films, displaying regular arrays of hexagonal micro-rods perpendicular to the substrate. Thus such a structure having hexagonal micro-rods in ZnS films is observed, to our knowledge, for the first time. The optical transmission measurements showed that both undoped and doped films had a low average transmittance between about 2 to 20 %. The gap energy is decreased from 3.44 eV for the undoped film to (a) 3.32 eV for the Mn-doped Zn(O,S) film annealed at 400 °C; to (b) 3,40 eV for the Co-doped Zn(O,S) film annealed at 450 °C and to (c) 3,37 eV for the Ni-doped Zn(O,S) film annealed at 450 °C. Clear ferromagnetic loops were observed for (a) the Mn-doped Zn(O,S) film annealed at 350 and 400 °C, for (b) the Co-doped Zn(O,S) film annealed at 400 and 450 °C and (c) the Ni-doped Zn(O,S) film annealed at 350, 400 and 450 °C.