Structural, Optical, Electronic and Magnetic Properties of Fe-Doped ZnO Nanoparticles Synthesized by Combustion Method and First-Principle Calculation

In this work, pure and Fe-doped ZnO were investigated in both experimental and theoretical aspects. The Zn1-x Fe x O (x=0.000, 0.0625, and 0.125) nanoparticles were prepared by a combustion method. The crystal structures were characterized by the X-ray diffraction (XRD) and selected area electron diffraction (SAED) analysis, morphology by the scanning electron microscope (SEM) and transmission electron microscopy (TEM) techniques, elemental analysis or chemical characterization by energy-dispersive X-ray spectroscopy (EDS or EDX), magnetic behavior by vibrating sample magnetometer (VSM), and optical band gap by ultraviolet-visible (UV-Vis) spectroscopy. In the first principle calculation, the structural properties, density of states (DOS), electronic band structure, and magnetic property of pure ZnO and Zn1-x Fe x O have been investigated by means of density functional theory with local density approximation (LDA), general gradient approximation (GGA), as well as LDA and GGA with Hubbard model scheme (LDA + U and GGA + U), packaged in the Vienna Ab initio Simulation Package (VASP). The calculation was performed using self-consistent projected augmented plane wave (PAW). The zinc oxide was modeled using 2×2×2 super-cell in ideal hexagonal wurtzite structure. The prepared samples of pure ZnO and Zn1-x Fe x O with iron concentration of 6.25 and 12.5 % by mole have a phase of the hexagonal wurtzite structure with particle size in nanometer scale. The calculation results indicate that the pure ZnO has direct energy band gap of 2.24 eV for GGA + U calculation in the scheme of Perdew–Burke–Ernzerh of PBE, which are underestimated when compared to the results from the experiment part, E g =.17 eV. The calculated magnetic dipole moments of the Zn1-x Fe x O when the iron contents (x) are 0.000, 0.0625, and 0.125 equal to 0.00, 3.91, and 7.83 μ b respectively. The density of states of dopant systems shows an intermediate band from d orbital of iron atoms located near the valence band. This indicates that small amount of doped iron engineers the band structure. These results show that the doped iron atoms seem to play an important role for the appearance of intermediate band and magnetism.