Influence of thermolysis temperature on the morphology, structural and optical properties of nanocomposite ZnS-polyvinyl alcohol thin films: Fabrication and characterization of indium tin oxide/ZnS-polyvinyl alcohol/Al Schottky diode

Abstract

Zinc sulfide-polyvinyl alcohol (ZnS-PVA) nanocomposite thin films were synthesized on glass substrates via solvent casting method followed by thermolysis technique. The thermolysis reactions were carried out at different thermolysis temperatures (Tt) ~80, 100, 120, 150, 200 and 250 °C to study the induced changes in the growth process. Thin films synthesized at Tt ~ 200 and 250 °C consist of ZnS nanoparticles with high crystallinity and distinct lattice fringes were observed by high-resolution transmission electron microscope. At Tt ~ 250 °C the PVA contents in the film diminishes given that agglomeration of crystallites takes place. X-ray diffraction and selected area electron diffraction patterns confirm the cubic phase of the ZnS-PVA thin films with preferred orientation along (111). The scanning electron micrographs reveal the homogeneous morphology and increase in grain size on the surface of thin films at higher thermolysis temperature. The thickness of the films determined using Swanepoel's method was found to decrease from 1700 to 350 nm when thermolysis temperature increases. The presence of different functional groups and the formation of bonds between Zn and S were confirmed by fourier transform infra-red spectrum analysis. The metal-semiconductor junction was synthesized by forming an indium tin oxide/ZnS-PVA/Al heterostructure. The behavior of metal-semiconductor junction was analyzed by current- voltage characteristics.