Temperature-Dependent Study of Optical, Electrical, and Structural Properties of Gadolinium-Doped Zirconium Sulphide Thin Films Fabricated Via Electrostatic Spray Deposition Technique for Optoelectronic Applications

Abstract

This study investigates the structural, optical, morphological, and electrical properties of gadolinium-doped zirconium sulphide (ZrS/Gd) thin films created using the Electrostatic Spray Deposition (ESD) method with respect to the effects of deposition temperature. Thin films deposited at 30°C, 34°C, and 36°C were compared to undoped ZrS. All samples exhibited a significant UV absorbance peak in the range of 340 to 400 nm during optical characterization; the absorbance was minimal at 36°C and maximum at 30°C, indicating a reduction in absorbance due to heat. In the visible and near-infrared ranges, transmittance rose with temperature, peaking at 36°C. Reflectance also increased with the deposition temperature, exhibiting a temperature-dependent trend. Non-linear temperature dependency was indicated by the optical band gap energies of 3.19 eV (pristine), 3.27 eV (30°C), 3.18 eV (34°C), and 3.58 eV (36°C). Electrical studies showed that when conductivities increased at 1.65 S/m, 1.78 S/m, 1.75 S/m, and 1.68 S/m, respectively, resistivity reduced from 0.6058 Ω·m (pristine) to 0.5614 Ω·m (30°C), increased slightly to 0.5717 Ω·m (34°C), and subsequently decreased to 0.5938 Ω·m (36°C). As the temperature rose, X-ray diffraction (XRD) examination revealed increased crystallinity and grain development, while SEM micrographs revealed a uniform distribution of nanoparticles free of pinholes. By serving as active nucleation sites, gadolinium ions encouraged the development of more homogeneous and densely packed grains. This eliminates pinholes by forming a film in which the grains more effectively fill in the spaces. These findings highlight the significant role of deposition temperature in optimizing the optoelectronic performance of ZrS/Gd thin films for potential applications in photonic sensors, solar cells, and display technologies.