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
Cletus Olisenekwu *
Department of Science Laboratory Technology, Delta State University, P.M.B. 1, Abraka, Delta State, Nigeria.
Samuel Oghenemega Shaka
Department of Science Laboratory Technology, Delta State University, P.M.B. 1, Abraka, Delta State, Nigeria.
Oyibo Dafe Precious
Department of Science Laboratory Technology, Delta State University, P.M.B. 1, Abraka, Delta State, Nigeria.
Imosobomeh L. Ikhioya
Department of Physics, Federal University Lokoja, P.M.B. 1154, Lokoja, Kogi State, Nigeria.
Raceforth Atori
Department of Science Laboratory Technology, Delta State University, P.M.B. 1, Abraka, Delta State, Nigeria.
*Author to whom correspondence should be addressed.
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.
Keywords: Gadolinium, zirconium-sulphide, electrostatic-spray, optoelectronics, bandgap, thin film, characterization