Investigation on the structural, optical and electrical properties of mixed SnS2-CdS thin films

Mixed thin films of (SnS2)x(CdS)1−x (0 ≤ x ≤ 1) were deposited by spray pyrolysis technique decomposition of aqueous solutions of Cadmium chloride (CdCl2) and Tin chloride (SnCl2) on glass substrates at a substrate temperature of 350 °C. Structural properties of the obtained films were studied by X-ray diffraction analysis. The surface morphology and elemental analysis of the films has been examined using scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX). Optical properties of the deposited films were obtained using transmittance measurements in the wavelength range [200-2500 nm].Some optical parameters such as, high frequency dielectric constant ε∞, lattice high frequency dielectric constant εL and the dispersion parameters (oscillation energy E0 and the dispersion energy Ed) were estimated by analyzing the refractive index data. The direct optical band gap value of these films varies from 2 to 2.41 eV. We have observed that (SnS2)x (CdS)1-x thin films conductivity obeys the Meyer-Neldel rule (EMN = 32 meV), which is interpreted as disorder parameter. The room temperature electrical resistivity of CdS (x = 0) films was found to be 2.22 10+4 Ω cm and it decreases when content of Sn in mixed films increases and reaches the optimum value of resistivity 2.32 10−2 Ω cm for the concentration x = 0.5. The carrier concentration was found to vary from −1.26 10+12 to −4.50 10+20 cm−3 and corresponding hall mobility varied from 6.51 10+1 to 2.64 10+1 cm2/VS.