Adsorption and reaction time effects on the properties of ZnS films grown by SILAR: an experimental study and DFT calculation

Abstract

In this work, the successive ionic layer adsorption and reaction method was used to synthesize and study the effect of immersion time in cationic and anionic solutions on the physical properties of zinc sulfide thin films (ZSTF). ZSTF were deposited onto glass substrates. X-ray diffraction analysis of the as-deposited ZSTF films revealed the formation of polycrystalline cubic structures with a dominant (111) orientation. These films exhibited improved crystallinity following 2 h of sulfurization at 400 °C. Using the absorption coefficient measurement, the gap energies of ZSTF for the immersion times 30 s, 40 s and 50 s were 3.84 eV, 3.8 eV, and 3.74 eV, respectively. Scanning electron microscopy and energy dispersive X-ray spectroscopy revealed a rough grainy morphology, and the obtained layers are formed with the stoichiometry of Zn and S. A density functional theory simulation was performed to calculate the gap energies of ZSTF, by generalized gradient approximation. The obtained results have shown a direct optical gap within the interval 2–2.5 eV. To improve the accuracy of electronic property calculations, using the TB-mBJ approximation, the energy gap was found to range between 3.61 and 3.82 eV These results are in good agreement with the experimental findings, which can promote the development of such materials for photovoltaic applications.