Structural, optical, magnetic and half-metallic studies of cobalt doped ZnS thin films deposited via chemical bath deposition

The results of experimental and theoretical study on structural, optical, magnetic and half-metallic properties of cobalt doped ZnS thin films deposited via chemical bath deposition are presented. Phase pure deposition of cubic ZnS with a slight variation in the lattice constant due to the incorporation of cobalt into the ZnS lattice is observed. It is shown that the crystallite size calculated by the Scherrer equation has an average value of 12 nm. The agglomeration of nanocrystallites leads to the formation of spherical clusters having an average diameter of 170 nm on the substrate surface. Room temperature ferromagnetism in cobalt doped ZnS thin films depending on cobalt concentrations is observed. Such behavior corresponds to the dopant-induced magnetism in the host semiconductor and agrees well with the theoretical predictions in addition to the observation of half metallicity. The variation in the band gap as a function of cobalt concentration is attributed to the structural modification after cobalt doping and occurrence of the quantum confinement phenomenon. Photoluminescence emission characteristics of the samples show the formation of luminescence centers of cobalt ions causing the radiative recombination processes. The increased intensity of PL emissions indicated that the concentration quenching effect did not appear up to the doping concentration of 12 at%.