Effect of Annealing Time on Structure, Morphology, and Optical Properties of Nanostructured CdO Thin Films Prepared by CBD Technique

Abstract

Nanostructured cadmium oxide (CdO) thin films were deposited onto glass substrates using the chemical bath deposition (CBD) technique. Different deposition parameters such as deposition time, bath temperature, pH, and CdSO4 concentration have been considered to specify the optimum conditions to obtain uniform and well-adherent thin films. The thin films prepared under these optimum conditions were annealed for different times (20, 40, and 60 min) at 300 °C, where no previous studies had been done to study the effect of annealing time. The XRD analysis showed that the as-deposited film is Cd(OH)2 with a hexagonal phase. While all the annealed films are CdO with a cubic phase. The crystallite size increases with the annealing time. However, the strain, dislocation density, and the number of crystallites were found to be decreased with annealing time. SEM images of annealed films showed a spherical nanoparticle with an average of particle size 80–46 nm. EDX analysis revealed that the ratio of cadmium to oxygen increases with increasing the annealing time to 40 min. The optical characterization shows that the transmittance is in the range of 63–73% and the energy gap is in the range of 2.61–2.56 eV. It has been found that the transmittance increased and the energy gap decreased with the annealing time. The prepared CdO films can be used in photodegradation applications to remove pollutants from water.

Keywords

• chemical bath deposition
• CdO thin films
• annealing time
• transmittance
• energy gap