Structure, photoluminescence, and magnetic properties of Co-doped ZnO nanoparticles
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Co-doped ZnO-nanoparticles were synthesized using the sol–gel method. The microstructure, morphology, and physical properties of the particles were studied using several analytical methods, including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–vis absorption spectroscopy, photoluminescence spectrometry, and vibrating sample magnetometry. The structure of the Co-doped ZnO nanoparticles was identified as hexagonal wurtzite, which suggests that Co2+ can replace the Zn2+ sites in the ZnO crystal lattice without forming a secondary phase. For Co-doped samples, the optical energy bandgap decreased with an increase in the Co content. The absorption-band edges were 565, 610, and 653 nm, which correspond to the d–d transition of Co2+ ions in the tetrahedral field of ZnO. The PL spectra revealed a strong defect-emission, which indicates that defects may stabilize the ferromagnetic order. Room-temperature ferromagnetism was observed in Co-doped ZnO nanoparticles according to M–H measurements. Furthermore, the magnetization increased with increasing Co concentration. These findings suggest that Co-doped ZnO nanoparticles could promote the development of semiconductor devices with ferromagnetic properties above room temperature in magneto-optical and spintronic applications.
This work was supported by grants from the National Natural Science Foundation (No. 61601359), Key Science and Technology Program Funded by Shaanxi Province Science and Technology Bureau (Program No. 16JS038), the Principal’s Foundation (Program No. XAGDXJJ15003) and Dean’s Foundation (Program No. 13GDYJY03) from Xi’an Technological University.
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