Influence of substrate activation process on structural and optical properties of ZnS thin films

•Substrate activation process is useful for the growth of ZnS thin films by chemical bath deposition method.•Aluminum ions become the nucleation center for the active ingredients of the deposition solution.•Carrier dynamics coincides with the build-up of the aluminum ions.•Green emission is related to vacancies sulfur and impurities of aluminum ions.

ZnS thin films were deposited on glass substrates by a chemical bath deposition method using a substrate activation process in which aluminum ions become “contaminants” that act as a nucleation center for active components within the deposition solution. The structure and morphology results demonstrate that the films have a ZnS sphalerite crystal structure with a particle size less than 15 nm, and the films consist of small homogeneous grains. The effects of the substrate activation process on the band gap energies and donor-acceptor pair luminescence process were also investigated. A green emission centered at 502 nm was produced due to donor-acceptor transitions from the aluminum acceptor to the ionized and substitution aluminum centers (Al3+).