Structural and Optical Analysis of Thin Film Semiconductor Materials Prepared by Sol-Gel Technique

Abstract

Solution-processed semiconductor thin films are attractive for optoelectronic and sensing applications because they can be produced at low temperature with inexpensive equipment and good control over composition. This methodology paper presents a reproducible sol-gel spin-coating route for structural and optical analysis of zinc oxide (ZnO) thin films as a representative wide-band-gap semiconductor. Zinc acetate dihydrate is proposed as the metal precursor, ethanol as solvent and monoethanolamine as stabilizer. Clean glass or quartz substrates are coated repeatedly, preheated to remove organic residues and finally annealed between 400 and 600 °C. The resulting films are evaluated by X-ray diffraction (XRD), scanning electron microscopy or atomic force microscopy (SEM/AFM), and UV-Visible spectroscopy. Crystallite size is estimated from the Scherrer relation, while the absorption coefficient and optical band gap are obtained from transmission data using a Tauc plot for direct allowed transitions. Literature available up to 2017 consistently shows that sol-gel-derived ZnO can develop a hexagonal wurtzite phase with preferential (002) orientation and visible-range transmittance commonly above 80%, while annealing, precursor concentration and film thickness strongly influence crystallinity and optical edge [1-10]. The proposed methodology therefore provides a practical framework for correlating processing conditions with crystal quality, surface morphology, transmittance and band-gap energy without requiring vacuum deposition equipment.