Fabrication of Zinc Oxide (ZnO) Nanorods on Aluminium Doped ZnO (AZO) Seeding Layers

Abstract

Aluminium-doped zinc oxide (AZO) thin films and ZnO nanorods (NRs) were synthesized and characterized to explore their structural, optical, and electrical properties. AZO seed layers with varying Al concentrations 2, 3, 5, and 8 mol% were deposited on soda-lime glass via spin coating, followed by hydrothermal growth of ZnO NRs. XRD and SEM confirmed vertically aligned, c-axis-oriented nanorods, with morphology influenced by doping and annealing temperature. Optimal crystallinity was achieved at 250 °C, while higher temperatures led to lattice relaxation and reduced structural quality. Photoluminescence revealed UV near-band-edge emission (~380 nm) and visible deep-level emission (500–700 nm), with DLE intensity suppressed at 8 mol% doping, indicating reduced defect density. Both AZO and ZnO NRs showed high optical transparency, and band gaps ranged from 3.44–3.55 eV (AZO) and 3.05–3.15 eV (ZnO NRs), tunable via Al doping. The electrical conductivity and film thickness were strongly influenced by both Al concentration and annealing conditions. The favorable combination of structural integrity, high transparency, tunable band gaps, and improved conductivity renders these AZO/ZnO nanostructures promising candidates for application in a wide range of optoelectronic devices.