Effect of deposition time on the structure, direct and indirect energy gap of nanoparticles CdO thin films deposited by chemical bath deposition technique

Abstract

In this research, cadmium oxide (CdO) nanoparticle thin films have been prepared at room temperature using a chemical bath deposition (CBD) technique, and the effect of the deposition time were studied. CdO thin films have been deposited on glass substrate from cadmium chloride (CdCl2) as cd +2 ions source and sodium hydroxide NaOH as O −2 ions source. The pH value (acidity level) of the chemical bath was fixed at about 11. The CdO thin films structures were analyzed by X-ray diffraction. It shows that all the prepared thin films have a cubic polycrystalline structure with a preferential orientation along (111) plane. All structural parameters were calculated. Particle size for the preferential orientation is calculated between (19.1-35.5 nm). It is found that the grain size increased with increasing the deposition time. UV-Vis spectrophotometer was used to study the optical properties, and a blue shift in the absorption peaks was noticed. The energy gap values (direct transition and indirect) calculated from the absorption spectrum located between (3.026-3.409 eV) for direct transitions and (2.197-2.917 eV) for indirect transitions, and this indicates that all CdO thin films prepared nanoparticles. We found that the energy gap decreased with increasing the deposition time.