Structural, optical and electrical properties of Ni-doped CdS thin films prepared by spray pyrolysis

Un-doped and Ni-doped cadmium sulphide (Ni-CdS) thin films were prepared by spray pyrolysis technique using perfume atomizer, from aqueous solution of hydrated cadmium chloride (CdCl2 center dot H2O) and thiourea (CS(NH2)(2) as sources of cadmium and sulphur ions respectively. We used hexahydrated nickel chloride (NiCl2 center dot 6H(2)O) as the dopant. The films were deposited on heated amorphous glass substrates at 400 degrees C. The effect of the [Ni]/[Cd] ratio on the structural, morphological, optical and electrical properties of these films was investigated. X-ray diffraction (XRD) studies revealed that all the deposited films (un-doped and Ni-doped CdS) were polycrystalline with hexagonal structure and exhibited [1 0 1] preferential orientation. The scanning electron microscopy (SEM) images showed a dense surface structure composed of crystallites whose average size decreases when the [Ni]/[Cd] ratio increases. The optical study showed that all the films were highly transparent. The transmittance in the visible region varies between 70% and 85%, depending on the dopant concentration. The film obtained with the [Ni]/[Cd] ratio equal to 4 at.% Ni showed minimum resistivity of 1.3 x 10(5) Omega cm at room temperature. (c) 2012 Elsevier B.V. All rights reserved.