NON-MONOTONIC EVOLUTION OF OPTICAL AND STRUCTURAL PROPERTIES IN ELECTRODEPOSITED SN- DOPED MGO THIN FILMS: AN OPTIMIZATION AND MECHANISTIC STUDY

Abstract

The strategic incorporation of tin (Sn) as a dopant into wide-bandgap semiconductors represents an established approach for bandgap engineering. Also, the development of multifunctional optical coatings that offer protection against ultraviolet (UV) degradation while minimizing reflective losses is necessary for enhancing the efficiency and durability of solar cells, display screens, and architectural windows. This study investigates the nonlinear and concentration-dependent effects of Sn doping on the structural and optical properties of magnesium oxide (MgO) thin films synthesized via electro-deposition. Films were fabricated with varying Sn precursor concentrations (2–10 mL) and characterized using X-ray diffraction (XRD) and UV–Vis spectroscopy. XRD confirmed a cubic MgO structure (Fm-3m) with a dominant (200) orientation and crystallite sizes ranging from 21.3 nm to 116.7 nm. Optical analysis revealed a pronounced non-monotonic trend: the 8 mL doped film exhibited maximum absorbance (~0.9) whereas lower (2, 4 mL) and higher (10 mL) concentrations resulted in anomalous or reduced performance, respectively. These films function as a dual-purpose optical coating exhibiting a strong UV-blocking capabilities, with absorption coefficients exceeding 5×10⁸ m⁻¹ in the 200-400 nm range, effectively preventing harmful radiation from penetrating the substrate. The films serve also as an anti-reflective layer in the visible spectrum, achieving low reflectance values of 15-20%. Notably, the 6 mL doped sample maintained a high visible transmittance of ~70% alongside a minimal reflectance of ~15%.These findings provide a crucial roadmap for defect engineering in electrodeposited MgO films.