Growth and Optical Absorption of CoIn2S4 Thin Films by Spray Pyrolysis Method

Abstract

CoIn 2 S 4 thin films were grown onto glass substrates by a spray pyrolysis method. For the growth, the substrate temperature was varied between 250 and 320 ∘ C, and the spray rate was fixed at 6 ml/min. The grown thin films were characterized X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), and optical spectroscopy. The XRD analysis showed that the thin films grown at 320 ∘ C were well crystallized in cubic spinel structure. The FE-SEM results demonstrated that the thin films have a uniform and homogeneous surface. The direct band gap energy was first obtained from the measurement of optical absorption spectra near the fundamental absorption edge at 292 K, and was founded to be 1.59 eV. We also observed two group absorption bands in the near-infrared region, which originate in cobalt ions of the constituent elements of CoIn 2 S 4 . The absorption bands were well assigned as due to the crystal-field transitions of Co 2 + ions occupying tetrahedral sites of the cubic spinel CoIn 2 S 4 host lattice.