Boosting UV Photodetection in ZnO Thin Films through Post-Deposition Annealing

Abstract

This work investigates the effect of post-deposition annealing on pristine 3 M ZnO thin films for ultraviolet (UV) photodetector applications. The films were annealed in air at 450 °C for 1 h in a muffle furnace, and their morphology, optical, structural, and electrical properties were systematically analyzed. Field emission scanning electron microscopy (FESEM) revealed a transition from irregular grains in pristine films to well-connected, densely packed nanostructures after annealing. UV-Vis absorption showed enhanced near-band-edge absorption, while photoluminescence (PL) spectra indicated suppressed deep-level emission, confirming reduced defect density. X-ray diffraction (XRD) analysis revealed improved crystallinity with a stronger (002) peak intensity and reduced FWHM after annealing. Current-voltage (I-V) measurements under UV illumination demonstrated a dramatic enhancement in responsivity, increasing from 43 A/W (pristine) to 1700 A/W (annealed). These results confirm that thermal annealing effectively tailors ZnO thin film morphology and optoelectronic properties, enabling high-performance UV photodetectors. © 2025 IEEE.