Substrate Temperature Effect on the Structural, Optical and Morphological Proprties of Cobalt Sulfide Thin Films Deposited Using Spray Pyrolisis

Abstract

Thin films of cobalt sulfide were grown on glass substrates at four different temperatures (250 °C, 300 °C, 350 °C and 400 °C) using spray-pyrolysis technique. The precursor solutions were prepared using cobalt chloride and thiourea. The effect of deposition temperature on the structural, morphological, and optical properties of cobalt sulfide thin films was investigated using different experimental techniques such as X-ray diffraction (XRD), and UV-visible spectrophotometry, Fourier Transform Infrared Spectroscopy (FT-IR) and four-probe method. The XRD analysis showed that crystallite size varies from 9.76 to 14.11 nm with increasing the deposition temperature. UV-visible data analysis shows a decrease in the band gap energies with increasing temperature (1.82 eV for 250 °C, 1.76 eV for 300 °C, 1.72 eV for 350 °C, and 1.65 eV for 400 °C). The analysis of the chemical composition by FTIR confirmed the presence of Co, S elements. On the other hand, the electrical conductivity of the cobalt sulfide thin films increased owing to the increase in the crystallite size and reduction of defects density.