Investigation the Optical and Structure Properties Of The Cd0.8Sn0.2Te Thin Films With different Thicknesses Deposited by Thermal Evaporation

Abstract

In this work, the structure and optical properties were studied for the Cd_0.8Sn_0.2Te. thin films prepared by thermal evaporation method with the following thicknesses: 400 nm, 600 nm, 800 nm were studied. The XRD phase analysis of the powder showed a polycrystalline structural. The surface analysis by the atomic force microscope (AFM) showed that the grain size of the prepared films decreases when increasing the films thickness and the films roughness also decreases when increasing the film thickness.

Also, the optical properties of the films were investigated in the range (350-800 nm) to estimate the film optical parameters, such as the refractive index, dielectric constant in real part(ε₁) and imaginary part (ε₂), the energy gap (E_g), the extinction coefficient (k) and optical conductivity (σ).

Based on this study, an indirect relationship was observed with the values ​​of these parameters with the film thickness. This could be explained by the randomness and structural defects resulting from existence of the 10% Sn in the studied Cd_0.8Sn_0.2Te thin films.

A decrease in the energy gap (E_g) of the thin films was observed by increasing the film thickness.