Integrating the structural, optical and dielectric behaviour of Al/Ti co-doped ZnO nanoparticles for optoelectronic applications

Abstract

In this study, Al/Ti co-doped ZnO nanoparticles were synthesized via the co-precipitation method. X-ray diffraction (XRD) analysis confirmed the preservation of wurtzite hexagonal crystal structure across all samples, without any secondary phases. Scanning and transmission electron microscopy (SEM and TEM) revealed that pure ZnO nanoparticles exhibited a nearly spherical morphology, which was mixed with some elongated particles with doping of Ti, indicating dopant-induced modifications in growth dynamics. Fourier-transform infrared (FTIR) spectroscopy identified the characteristic Zn–O vibrational modes, with slight variations in intensity corresponding to the presence of dopants. X-ray photoelectron spectroscopy (XPS) analysis indicated the formation of oxygen vacancies, evidenced by the broadening and shifting of O 1s peaks, suggesting successful incorporation of Al and Ti into the ZnO lattice. UV–Visible spectroscopy showed a blue shift in the absorption edge and an increase in the optical bandgap, attributed to quantum confinement. The dielectric constant increased significantly, ∼450 for Al/Ti co-doped ZnO, accompanied by low dielectric loss, which is likely due to enhanced defect polarization and the presence of oxygen vacancies. Furthermore, electrical conductivity was improved, potentially due to an increase in charge carrier with dopant ions. These findings demonstrate that Al/Ti co-doping make ZnO as promising candidate for optoelectronic and high-frequency electronic devices.