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

Mixed thin films of (SnS 2 ) x (CdS) 1−x (0 ≤ x ≤ 1) were deposited by spray pyrolysis technique decomposition of aqueous solutions of Cadmium chloride (CdCl 2 ) and Tin chloride (SnCl 2 ) 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 e ∞, lattice high frequency dielectric constant e L and the dispersion parameters (oscillation energy E 0 and the dispersion energy E d ) 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 (SnS 2 ) x (CdS) 1-x thin films conductivity obeys the Meyer–Neldel rule (E MN = 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 cm 2 /VS.