A comparison of chemical bath deposition of CdS from a batch reactor and a continuous-flow microreactor

In this paper, we report a comparison between CdS deposition by a conventional batch reactor and a newly developed continuous-flow microreactor. This microreactor setup makes use of a micromixer for efficient mixing of the reactant streams and helps in controlling the homogeneous reaction before the solution impinges on a substrate. Transmission electron microscopy analysis indicated that an impinging flux without the formation of nanoparticles could be obtained from this reactor at a short residence time. The surface morphology of the deposited films clearly indicated an improvement of film smoothness and coverage over films deposited from a batch process. Highly oriented nanocrystalline CdS films were obtained from the continuous-flow microreactor in contrast to poor crystalline films from the batch process. This new approach could be adopted for the deposition of other compound semiconductor thin films at low temperatures using a solution-based chemistry with improved control over the processing chemistry.