“…A chemical bath deposition (CBD) procedure, where a cadmium salt and thiourea are taken as sources of cadmium and sulfur ions, while ammonia works as a complexing agent and makes a basic medium for thiourea hydrolysis, is widely used for the formation of CdS thin films. , The structure and properties of deposited film depend on the temperature and duration of synthesis, , the type of cadmium salt, , the concentration and ratio of the reagents, , the pH of solution, , and the used substrate. , Despite a long time of investigation of this process, the mechanism of CdS deposition is still unclear. At present, two ways of CdS formation are considered in the literature: (1) nucleation and growth directly on the substrate, a heterogeneous or so-called “ion-by-ion” process, and (2) solution growth of CdS nanoparticles accompanied by their precipitation and aggregation on the substrate, a homogeneous or so-called “cluster-by-cluster” process. , In an ammonia–thiourea bath, cadmium ion may attach ammonia, hydroxide ion, and thiourea thus forming a single or mixed ligand complex. , The complexes are adsorbed on the substrate, and a heterogeneous growth process takes place by an ion exchange reaction with sulfur ions or through a breaking of S–C bond in the thiourea coordinated to cadmium .…”