Morphological Evolution and Optical Modeling of ZnO/Mn/ZnO Multilayer Thin films via Mn Interlayer Engineering

Abstract The influence of Mn on the structural and optical characterization of ZnO/Mn/ZnO multilayer thin films has been systematically investigated. Thin film samples with Mn layer thickness between 0-80nm were prepared by using a combination of atomic layer deposition (ALD) for ZnO, and direct current magnetron sputtering (DC) for Mn interlayer. The addition of Mn between the ZnO layers alters the electronic structure and defect distribution of the system, leading to observable changes in optical response. The thickness, morphology and optical response of the thin films under study were examined via X-Ray reflectivity (XRR), focused on the ion beam (FIB) cross-sectioning, scanning electron microscope (SEM). XRR analysis revealed an increase in surface roughness of the films and Mn layer density with higher Mn thickness, indicating improved Mn layer compactness, while FIB and SEM analysis confirmed the thickness and showed relatively sharp interfaces. From the measured transmittance and reflectance (T& R) spectra, a decrease in the refractive index n and the valence and surface electron energy loss functions ( VELF and SELF ), while an increase in the extinction coefficient k , dielectric constants (\(\:{\epsilon\:}_{1}\) and \(\:{\epsilon\:}_{2}\) ) ,and optical and electrical conductivity (σ opt ) and (σ elec ) ), highlighting the tunability of the optical properties with Mn interlayer thickness. The comprehensive analysis of the optical parameters derived confirms that controlled Mn interlayer provides an effective strategy for tuning the electronic and optical properties of ZnO/Mn/ZnO multilayers, making them promising candidates for advanced optoelectronic and photonic applications.