Probing into the optical and electrical properties of hybrid Zn_1−xCo_xSe thin films

Abstract

Probing into the elemental composition, structural, morphological, optical and electrical transport properties of chemically deposited Zn_1−xCo_xSe (0 ≤ x ≤ 0.275) thin films with a special emphasis given to the Co²⁺-concentration is presented in this paper. Elemental and structural analysis confirmed the successful realization of Co(ZnSe) thin films. Addition of Co²⁺ into ZnSe host lattice caused morphological changes from globule like morphology to the formation of leaf like appearance composing the disc-decked micro-flakes elongated in size. The optical studies done in the range of wavelengths between 350 to 1200 nm showed a slight red shift in the optical spectrum with increased Co²⁺ concentration in the ZnSe matrix. Effect of increased impurity addition is also reflected in the band gap measurements that a decrease in the bandgap, typically from 2.71 to 1.96 eV, is observed for an increase in Co²⁺ concentration from x = 0–0.275. The other optical parameters namely, refractive index, extinction coefficient, power factor and dielectric constants were determined from these studies and other variations are adequately explained as a special reference to the Co-concentration. The composition dependence of the electrical transport characteristics were studied using the two-probe and Hall measurement techniques. The effect of Co-concentration on the transport characteristics has been studied and mechanism of an electrical conduction is discussed. A continuous increase in an electrical conductivity with n-type conduction has been observed for these samples.