The influence of diffusion temperature on the structural, optical and magnetic properties of manganese-doped zinc oxysulfide thin films

We investigated the structural, optical and magnetic properties of Mn-doped zinc oxysulfide films. Zn(O,S) films were deposited by a spray pyrolysis method on glass substrate. A thin Mn layer evaporated on these films served as the source for the diffusion doping. 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 (0 0 2) hexagonal plane direction. SEM showed a similar surface morphology for the undoped and Mn-doped films, displaying regular arrays of hexagonal micro-rods perpendicular to the substrate. The optical transmission measurements showed that both undoped and Mn diffusion-doped films had a low average transmittance less than about 10%. The gap energy is decreased from 3.42 to 3.33 eV upon annealing at 400 °C. Photoluminescence studies at 300 K show that the incorporation of manganese leads to a decrease of deep level band intensity compared to undoped sample. Clear ferromagnetic loops were observed for the Mn-doped Zn(O,S) films, which might be due to the presence of point defects.