Influence of (Co+Al) co−doping on structural, micro-structural, optical and electrical properties of nanostructured zinc oxide

Abstract

This study investigates the effect of (Co + Al) co−doping on the physical properties of the ZnO nanoparticles, synthesized via the simple co−precipitation method. X−ray diffraction (XRD) analysis revealed a hexagonal structure for all samples, with a formation of Al2O3 phase in both Zn0.98Co0.01Al0.01O and Zn0.94Co0.01Al0.05O nanoparticles. The crystallite size increased from 26.5 nm for ZnO to 16.6 nm for Zn0.94Co0.01Al0.05O nanoparticles. Scanning electron microscopy (SEM) technique showed a notable alteration in the morphology of ZnO upon the incorporation of Al. A transition from spherical nanoparticles in ZnO and Co doped ZnO to irregular, dendritic-like structures in (Co + Al) co−doped nanoparticles is observed. Transmission electron microscopy (TEM) substantiated the presence of the Al2O3 phase in the co−doped samples. Raman and FTIR spectroscopy confirmed the incorporation of Co and Al into the ZnO lattice through the presence of Co–O–Co and Al–O bonds. Optical characterization indicated a decrease in the band gap energy from 3.18 eV in ZnO to 2.84 eV in Zn0.94Co0.01Al0.05O nanoparticles. Electrical conductivity measurements revealed an increase from 1.2 × 10−4 Ω−1 cm−1 to 1.8 × 10−3 Ω−1 cm−1 as the Al content increased from 0 % to 5 % at the frequency of 103 Hz and the temperature of 423K. Likewise, dielectric constant raised from 775 in ZnO to 5455 in Zn0.94Co0.01Al0.05O nanoparticles at the temperature 423K. These results highlight the potential of (Co + Al) co−doped ZnO nanoparticles for advanced optoelectronic applications.