Study of the early growth stages of chemically deposited ZnS thin films from a non-toxic solution

Abstract

ZnS thin films grown by the chemical bath deposition method have been under intense investigation due to their applications in solar cells. In this work, the early growth stages of ZnS thin films deposited by means of a non-toxic solution are studied by measuring the morphological, chemical and optical properties of the films obtained at different deposition time (5, 10, 20, 30, 60, 90 and 120 min). From the atomic force microscopy (AFM)studies, it was seen that the substrate surface is not fully covered before 20 min, and the growth exponential value changed from 0.5 to 1.8. The x-ray photoelectron spectroscopy (XPS) measurements revealed the presence of the Zn–O bond and the absence of the S– Zn bond at the earliest deposition time. Additionally, from XPS analysis, a shift in the signals for O1s and Zn2p3/2 for the sample grown at 30 min was observed due to the formation of Zn(OH)2. Finally, the UV-Vis spectrophotometry measurements showed that all samples have a high transmittance (>80%) and that the band gap value decreased as the deposition time increased.