Structural, Optical, and Nonlinear Optical Properties of ZnO Nanostructures Grown on Porous Silicon

Abstract

Zinc oxide (ZnO) nanostructures were effectively produced on a porous silicon (PS) substrate using thermal evaporation, thereafter undergoing oxidation at 600 °C. The structural, morphological, elemental, optical, and nonlinear optical (NLO) characteristics of the synthesized films were methodically examined. X-ray diffraction research indicated that the ZnO/PS films possess a polycrystalline hexagonal wurtzite structure with a preferential orientation along the (101) plane, and the average crystallite size was calculated to be around 3.8 nm, affirming their nanocrystalline characteristics. Scanning electron microscopy pictures revealed the presence of agglomerated nanostructures and nanorods over the PS surface, signifying elevated surface roughness and extensive surface area. Energy-dispersive X-ray investigation verified the predominance of Zn and O, with modest contributions from Si originating from the substrate. The optical absorption spectra exhibited a significant blue shift attributable to quantum confinement phenomena, with the optical band gap measured at approximately 3.6 eV. The calculated Urbach energy (Eu = 145 meV) indicates a moderate level of structural disorder and the presence of tail states near the band edge, aligning with the nanocrystalline characteristics of ZnO films. The Z-scan approach utilized for NLO measurements demonstrated saturable absorption behavior, suggesting possible applications in photonic and optical limiting devices. Received: 2 December 2025 | Revised: 12 January 2026 | Accepted: 11 February 2026

Conflicts of Interest

The authors declare that they have no conflicts of interest to this work.

Data Availability Statement

Data are available from the corresponding author upon reasonable request.

Author Contribution Statement

Marwa. K. Abood: Conceptualization, Methodology, Validation, Resources, Project administration. Wafaa Khalid Khalef: Conceptualization, Methodology, Validation, Supervision. Amenah Ali Salman: Software, Formal analysis. Nibras Salah Hameed: Investigation, Data curation, Writing – review & editing. Mohammed Khalid Khalaf: Writing – original draft, Visualization.