Incipient growth of CdS films from weakly supersaturated solutions

The initial period of CdS film growth appears to strongly influence the quality of the final film. Scanning electron microscopy pictures of film grown by the flow of a supersaturated (in CdS) solution suggest that nuclei are continuously generated on the substrate and grow as discrete “surface” particles. With time, these growing particles grow and “coalesce” with neighbouring ones to create a continuous film. Similar growth patterns are also observed in the chemical bath deposition process. A simple model of the process is developed employing a “unit cell” approach, which is capable of addressing issues such as the existence of an “induction period” in film growth and its relation to supersaturation, in addition to predicting film thickness growth.