Chemical bath deposited Mg_xZn_1-xS(O) thin films and their photoluminescence properties

A zinc sulfide (ZnS) specimen was intentionally doped with transition metal (Mg-donor) elements using a chemical bath deposition (CBD) technique. Both the un-doped and the magnesium (Mg)-doped ZnS samples were confirmed to have hexagonal wurtzite ZnS crystal structure. The XRD patterns showed no characteristic peak for Mg indicating that the Mg²⁺ ions had been incorporated into ZnS(O) lattice sites. In contrast to un-doped samples, Mg doping resulted in changes in the morphological features of the spherical clusters which resulted in porous, spongy vermicular structures. The energy band gap of the Mg_xZn_1-xS(O) film was slightly larger than that for the ZnS(O) film. A photoluminescence study revealed that the emissions were near violet-blue-green in color. The emission characteristics consist of two components; emission in the near violet and in visible region. That is the first is between 4160 and 4400 Å and the second is at 5190 Å, and these are associated with the donor-acceptor transitions with sulfur vacancies as acceptors and the magnesium related defects (trap states) in the samples respectively.