Abstract:
A well adherent single layer thin film of zinc oxide (ZnO), zinc sulfide (ZnS), cadmium oxide (CdO) and cadmium sulfide (CdS) has been deposited on silica glass substrates from basic baths containing zinc acetate, cadmium acetate, ammonium hydroxide, triethanolamine, thiourea, and sodium hydroxide as precursors by chemical bath deposition (CBD), followed by multilayer deposition of metal oxide/metal sulfide and metal sulfide/metal oxide then intercalated by polyvinyl alcohol (PVA). CBD was used for the deposition of the metal sulfide/oxide thin films under acidic and basic conditions for single layer thin film by varying temperature and pH. SEM micrograph of the as-deposited ZnS, ZnO, CdO, and CdS thin film, show the film to be uniform, dense, homogeneous at lower temperatures and composed of large irregular shaped grains that are scattered at higher temperatures. These large grains are comprised of smaller spherical grains. Star shapes were observed for ZnO and ZnS thin films while spherical shapes were observed for CdO and CdS thin films.
The effect of temperature on the optical properties was studied by varying the deposited films at different temperatures of 60˚C, 70˚C, and 90˚C. The increase in temperature on the single layer depositions caused the decrease in %T which was in support with the large SEM results which in higher absorbance. Films of different thickness of (114.4 nm, 107.7 nm, 100.4 nm, and 99.67 nm) respectively were obtained for single layer deposition. The XRD study of the ZnS, ZnO, CdO, and CdS monolayer films deposited does not reveal any well-defined peak, indicating a highly disordered material. The XRD of CdO thin films showed one broad peak around 2θ value 26.37° corresponding to (111) plane. The structural studies had similar behavior of CdS, ZnO, and ZnS was similar with CdO with one broad peak at 2θ ~ 26˚.
To enhance the property of MO, MS thin film was formed on the interfaces of MO thin film as a passivation and a substrate layer at 60°C with a pH value of 11 for 60 minutes deposition time and vice versa for enhancing the property of MS. The structural, morphological and optical properties of CBD deposited thin films have been studied by varying the processing parameters and the MO/MS multilayer ratio of the starting
v
precursors to provide a better understanding of the growth conditions by studying the MO/MS and MS/MO multilayer thin film materials with further intercalation of polyvinyl alcohol (PVA). Multilayer thin films show different physical properties other than the conventional monolayer thin films. The films were deposited as the matrix of MO/MS and MS/MO of respectively at temperatures of 60˚C at alkaline medium for 60 minutes deposition time. SEM micrograph of CdO/CdS was observed to be spherical shapes which show the film to be uniform, dense, and homogeneous. Large spherical particles that appear to be increasing in size and non-homogeneous were observed in the deposition of CdS/CdO. The deposited ZnO/ZnS thin films show large conglomerate of snowflake structures and that of ZnS/ZnO thin film were polycrystalline in structure. The optical properties and band-gap energy were studied by depositing the films at 60˚C for 60 minutes.
