Preparation and effect of complexing agents on ternary FeZnS₂ thin films by chemical bath deposition method for photo catalytic degradation of dye molecules

Abstract

In the present paper the studies on iron zinc sulphide thin films that have been deposited at room temperature on to the glass slides by chemical bath deposition technique using a solution mixture of ferrous sulphate, zinc sulphate, sodium sulphide, EDTA and Leishman stain is reported. Both EDTA and Leishman stain act as complexing agents and are expected to play a main role in the growth of FeZnS₂ thin films. The structure of FeZnS₂ thin films analysed by X-ray diffraction (XRD) study reveal that the thin films have a multi crystalline feature together with a solid three dimensional appearances at room temperature. The microstructure and the surface texture of the deposited filmsare characterised using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM images show that the deposited films have a fine texture due to the presence of complexing agents. AFM studies revealed that the grain size of the deposited films to be around 80–100 nm with the thickness being approximately uniform. FTIR spectral studies of the thin films were recorded between 400 and 7000 cm⁻¹. FeZnS₂ thin films illustrated excellent optical properties with great absorbance in the visible region. The band gap value found to be 2.37–2.77 eV. The Hall Effect measurements show that the FeZnS₂ thin films to have a n-type behaviour which exhibits p-type behaviour after the addition of complexing agents which is an ideal condition for solar cell applications. Towards this direction, the photo catalytic activities of FeZnS₂ thin films were also assessed by the degradation of crystal violet, malachite green and methylene blue in aqueous solution under sun light irradiation.