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

We investigated the structural, optical, and magnetic properties of Ni-Zn(O,S) films. The Zn(O,S) films were deposited by a spray pyrolysis method on glass substrate. A thin Ni layer evaporated on these films served as the source for the diffusion doping. The XRD of the undoped films revealed the presence of two wurtzite phases corresponding to zinc sulfide (ZnS) and ZnO with a strong preferred orientation along the ZnS [002] direction. Results from scanning electron microscopy showed arrays of hexagonal micro-rods perpendicular to the substrate. Results from energy dispersive X-ray spectroscopy studies employing varying accelerating voltages suggested that Ni atomic concentration decreased towards to the back of the films in all Ni diffusion-doped samples but a more uniform distribution was obtained at increasing annealing temperatures. The optical transmission measurements showed that both undoped and Ni diffusion-doped films had a low average transmittance in the range of 8-35%. Adecrease in the band gap was observed with Ni-doping from 3.44 to 3.38 eV upon diffusion-doping. The magnetization of films as a function of magnetic field and temperature were measured. Clear ferromagnetic loops were observed for the Ni-Zn(O, S) films. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim