The impact of thiourea concentration on the Structural, surface morphologyand optical characterization of chemically deposited CdS-PVA nanocomposites thin films

Abstract

In this research, CdS/PVA nanocomposites films were prepared on glass substrates using the chemical bath deposition (CBD) method. The effect of thiourea (TU) concentrations (0.1, 0.15, and 0.2) M on the crystal structure, topography, morphology and optical characteristics of the prepared nanocomposites film was investigated. The crystal structure from (XRD) results of all films was seen to be polycrystalline structure in nature of cubic phase for CdS, and presents a wide peak of 2θ about 22o for PVA polymer. The CdS-PVA nanocomposites film crystallinity was enhanced and the crystallite size was increased from (10–14) nm with the increase of TU molar concentrations from (0.1–0.2) M and the (111) plane is the favored orientation. The AFM results revealed that the film roughness and root mean square roughness were increased with the increase of TU concentrations. The surface morphology results from FESEM micrographs showed that the CdS-PVA nanocomposites film surface tended to be porous at all TU concentrations and the pore size increases with TU concentration. The optical absorbance and Transmittance spectra revealed that the fundamental absorption edge blue was shifted towards the short wavelengths and higher energies with the increase of TU molarity concentration. However, the absorption coefficient values were greater than 104 cm-1 and the energy gap was raised from 2.13 eV to 2.43 eV for 0.1 and 0.2 TU concentrations. It can be concluded from these results that the porous CdS-PVA nanocomposites film was suitable for photovoltaic and gas sensing applications.

Keywords

• Cadmium sulfide
• Polyvinyl alcohol
• Nanoparticles
• Thiourea