Voltage-Driven Electro-Spray and Optoelectronic Evaluation of Gd-Doped Zirconium Sulphide Thin Films for Enhanced Optoelectronic Device Applications

In this study, Gd-doped zirconium sulphide (ZrS/Gd) thin films were successfully synthesized using an electro-spray deposition technique at varying deposition voltages of 10.5 V, 11.0 V, and 11.5 V, aimed at optimizing their structural, optical, and electrical properties for photonic and optoelectronic applications. UV–Vis spectroscopy revealed enhanced absorbance in the UV region (300–400 nm), with 0.75 a.u absorbance at 11.5 V, while transmittance peaked at ~85% for the 11.5 V sample in the visible range. The calculated optical bandgap values decreased from 3.62 eV at 11.5 V to 3.21 eV at 10.5 V, indicating improved photon absorption with increased voltage. Optical conductivity reached a maximum of 0.73 S/m at 11.5 V, and refractive index peaked at 3.0 around 3.4 eV photon energy. Electrical analysis showed enhanced conductivity, increasing from 1.65 S/m in the undoped ZrS to 1.89 S/m at 11.5 V, while resistivity dropped from 0.61 Ω·m to 0.53 Ω·m. XRD analysis confirmed improved crystallinity and reduced dislocation density at higher voltages, with crystallite size ranging from 178 nm to 200 nm. SEM micrographs revealed uniform film deposition and nanoparticle agglomeration with no pinholes. These findings show that Gd doping and voltage-controlled deposition significantly enhance the optoelectronic properties of ZrS thin films, making them promising candidates for optoelectronics and photonics devices.