Effects of Ni concentration on structural, magnetic and optical properties of Ni-doped ZnO nanoparticles

Ni-doped zinc oxide (Zn-1 xNixO, 0 <= x <= 0.08) diluted magnetic semiconductors have been synthesized by the using a sol-gel method. Structural, magnetic and optical properties of the samples have been studied. The results of X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray absorption fine structure (XAFS) indicated that Ni ions were substitutionally incorporated into the crystal lattice of ZnO. With Ni concentration increasing up to 2 at.%, all diffraction peaks corresponded to wurtzite structure of ZnO, but for Zn0.97Ni0.03O, secondary phase of NiO emerged. Based on the results of X-ray photoelectron spectroscopy (XPS), Ni incorporated into the ZnO lattice as Ni2+. The produced samples showed good high-Tc (Curie temperature) ferromagnetism. The results of vibrating sample magnetometer (VSM) and photoluminescence (PL) showed that ferromagnetism (FM) of the Ni-doped ZnO nanoparticles originated from the presence of the O vacancy. (C) 2014 Elsevier B.V. All rights reserved.