Annealing Effect on The Structural and Optical Properties of CuS Thin Film Prepared By Chemical Bath Deposition (CBD)

Abstract

Thin films of copper sulfide (CuS) with various molarities values of Cu concentrations (0.2,0.3,0.4)M have been prepared by Chemical Bath Deposition Technique on glass slides substrate at room temperature . The prepared films with different ion concentrations were annealed in air at constant temperature 400 ºC and constant time (180) min .Structural and optical properties of CuS thin films were investigated and analyzed extensively before and after annealing . The structure of the prepared films has been found with amorphous structure at different Cu ion concentrations , annealed CuS films also showed amorphous structure. The optical properties of CuS thin films has been studied by transmittance and absorbance spectral in the range of wave length (190-1100)nm by using UV- Vis. spectrophotometer. Transmittance decreased with increasing the Cu ion concentrations of CuS films, also the transmittance increased with annealing process for (CuS) thin films. The fundamental absorption edge of (CuS) thin films shifted to word the lowest photon energies with increasing the Cu ions concentrations before and after annealing. From the absorption coefficient values which calculated from the absorbance spectrum which is larger than 10-4cm-1 gives an indicate that CuS films were direct semiconductors and the electronic transition was a direct transition. The optical energy gap values of CuS thin films for allowed direct transition found vary in the range between (2.433-2.526) eV with (0.2- 0.4 M) Cu ions concentration and in the range of (2.416-2.349) eV for the same concentrations after annealing. The optical constant such as reflectance ( R ), absorption coefficient (α), refractive index (n) and extinction coefficient (K) were evaluated and analyzed .