Physical Properties and Sensing Properties of Iron (II) Ion-Doped Zinc Sulfide Nanostructured Thin Films Deposited via Chemical Spray Pyrolysis

Abstract

Nanostructured thin films of Iron (Fe)-doped Zinc Sulfide (ZnS) were deposited via the Chemical Spray Pyrolysis (CSP) technique, with varying concentrations of Iron incorporated into the ZnS matrix. XRD analysis confirmed that all films preserved a zinc blende cubic structure, while the calculated average crystallite size increased from 13.25 nm for pure ZnS to 14.8 nm for Fe-doped samples. The structural investigation further demonstrated that Iron incorporation influenced lattice parameters, microstrain, and dislocation density, thereby reflecting measurable changes in overall crystal quality. Atomic Force Microscopy (AFM) revealed a relatively smooth and uniform surface topography, supporting the good quality of the prepared thin films. Optical properties were systematically examined using UV-Visible spectroscopy, which showed a clear dependence of band gap energies on Fe concentration, indicating that Fe ions effectively substituted Zn sites. Gas sensing measurements toward NO₂ at 125°C highlighted that Fe doping generally reduced sensitivity; however, thinner films exhibited enhanced responsiveness due to their larger surface-to-volume ratio and the presence of more active interaction sites. These results suggest potential for tailoring ZnS-based materials in optoelectronic and sensing applications.