Optical Properties of Silver Aluminium Sulphide Ternary Thin Films Deposited by Chemical Bath Method

Abstract

Ternary thin films of Silver Aluminium Sulphide (AgAlS₂) have been prepared by chemical bath deposition techniques. Aqueous solution of 41.5 mls containing AgNO₃, Al₂(SO₄)₃, thiourea and EDTA was used, where AgNO₃, Al₂(SO₄)₃, thiourea were the source of Ag⁺, Al⁺ and S^- respectively and EDTA was used as a complexing agent. NaOH served as pH adjuster. The films were deposited at 300K of temperature. The deposited film properties were studied using a Janway UV – VIS spectrophotometer. From the spectral analysis of absorbance and transmittance, the optical and solid properties were obtained. The properties studied include the reflectance, absorption coefficient, thickness, refractive index, extinction coefficient, optical conductivity and band gap energy. The films show high absorbance in the UV region and high transmittance in the VIS – NIR regions, while reflectance is generally low. The films showed direct band gap energy range of 2.15 eV – 2.40 eV and a refractive index of 2.64.

Key words: Chemical Bath, Ternary Thin Film, Optical Properties, Surface Morphology, Compositional properties