Impact of Gamma Irradiation on the Optoelectronic Properties of Al-Doped ZnO Thin Films

Abstract

This study presents a systematic investigation into the effects of gamma (gamma) irradiation (1-4 kGy) on the structural, optical, and electrical properties of aluminum-doped zinc oxide (AZO) thin films deposited by radio frequency (RF) magnetron sputtering. The films were analyzed using fiber-coupled optical spectroscopy, spectroscopic ellipsometry (SE), X-ray diffraction (XRD), and current-voltage (I-V) measurements to assess irradiation-induced alterations. Optical transmittance exhibited a dose-dependent reduction. The optical bandgap decreased from 3.43 eV to 3.25 eV, which we attribute to defect-induced tail states in the band structure. SE results indicated a gradual decrease in the refractive index and extinction coefficient with increasing radiation dose, reflecting changes in the material's dielectric response. XRD analysis revealed significant structural degradation, as evidenced by reduced peak intensities and increased full width at half maximum (FWHM), particularly for the (100) crystallographic orientation, suggesting decreased crystallinity and enhanced lattice disorder. Electrical characterization showed an increase in sheet resistance from 146 Omega/square to 298 Omega/square and a corresponding decrease in electrical conductivity, attributed to carrier trapping at radiation-induced defect sites and reduced mobility. The combined structural, optical, and electrical findings clearly understand the mechanisms underlying radiation-induced degradation in AZO thin films, which is crucial for evaluating its reliability in radiation-prone environments.