Theoretical Analysis of the Solid State and Optical Characteristics of Calcium Sulphide [CaS] Thin Film

Abstract

The analysis of the calcium sulphide thin film material which is one of the families of chalcogenide groups of thin film materials was carried out in this work using a theoretical approach for which the propagated wave through the medium of the thin film that is deposited on a glass substrate is considered to be a scalar wave in nature. The thin film material is sectioned into twos, first section is termed homogeneous reference dielectric constant, εref where no thin film is deposited on the substrate and the second part is termed perturbed dielectric function, Δεpz containing the deposited thin film on the glass substrate. These two terms were substituted on the defined scalar wave equation that was subsequently solved using the method of separation of variable which invariably utilized in the transformation of the equation into the second type of Volterra equation. On the other hand, Green’s function approach was also introduced in order to arrive at the model equation that culminates in an expression showcasing the wave propagated through the thin film material medium. This was subsequently applied in the computation of waves, ψz that is propagating through the material medium for various wavelengths within the ultraviolet, visible, and near-infrared region of the electromagnetic wave spectrum for which the influence of the aforementioned dielectric constant and function were invoked. The computed values from this mechanism were in turn utilized in the analysis of the band gap, optical, and solid-state properties of the calcium sulphide (CaS) thin film materials.