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

Lead Silver Sulphide (PbAgS) thin films on glass substrate have been deposited by chemical bath deposition technique with EDTA and TEA as complexing agents, while ammonium solution served as pH adjuster. The films were deposited at room temperature of 300K. The deposited films were characterized using UV – VIS spectrophotometer. From the spectral analysis of the absorbance / transmittance values, the optical and solid state properties were deduced. The optical properties studied include reflectance, absorption coefficient, thickness, refractive index, extinction coefficient, optical conductivity and band gap energy. The films showed very high absorbance in the UV region, moderate in the VIS region and low in NIR region. Transmittance is low in the UV region and high in the VIS – NIR region, while reflectance is generally low in all spectral region studied. The films showed a direct band gap range of 2.20 eV – 2.40 eV, refractive index range of 2.1 – 2.60, while the thickness of the films increases with deposition time