Optical Properties of Chemical Bath Deposited Magnesium Sulphide Thin Films

Abstract

Thin films of Magnesium Sulphide were deposited on a glass substrate at room temperature (300K) from aqueous solution of Magnesium Sulphate (MgSO₄.7H₂O), Ammonia (NH₃), Thiourea (NH₂)₂CS in which Ethylene diamine tetra acetate (EDTA) as complexing agent. Distilled water was used to make up the solution to the required volume. After the deposition, the films were optically characterized using M501 Single Beam Scanning UV/Vis Spectrophotometer. The results indicate that films exhibited low absorbance values (0.055-0.244) and reflectance values (0.067-0.186) respectively within the visible region of electromagnetic spectrum. The films show corresponding high transmittance value of 57%-91% within this region. The calculated absorption coefficient values of 0.683 x 10⁵- 7.630 x 10⁵m were recorded for the films with high optical conductivity values of 0.256 x 10¹³S^-1 – 4.579 x 10¹³ S^-1 in the visible region. The films were observed to possess low extinction coefficient values of 0.003-0.019 and poor imaginary dielectric function values of 0.010- 0.097. The calculated refractive index value was found to range from 1.56- 2.51. The films also exhibited direct wide band gap energy value of 3.85eV. All these desirable properties made the material a good candidate for photo-voltaic and photonic applications.

Keywords: Absorbance, reflectance, transmittance, optical conductivity, extinction coefficient, absorption coefficient, refractive index, dielectric function and band gap energy.