Experimental and first-principles studies of structural and optical properties of rare earth (RE = La, Er, Nd) doped ZnO

Rare earth (RE = La, Er, Nd) doped ZnO nanopowders were prepared by the chemical method. The structure and morphology of the synthesized samples were systematically investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The results showed that REs were incorporated into ZnO lattices and formed nanopowders. Absorption spectra of doped ZnO exhibited enhanced optical absorption in visible region, and photoluminescence (PL) study revealed that pure and REs doped ZnO had different I-UV/I-DLE ratios, which was also correspond to the structural analyses. In addition, the electronic structures of pure and REs doped ZnO were studied by the first-principles method. It was indicated that the Fermi levels shifted upward into the conduction bands and obtained n-type conductivities after REs doping. The calculated optoelectronic properties of REs doped ZnO were mainly affected by the 4f electrons of Er/Nd and 6s electrons of La, which were closed to the Fermi-levels and had a significant impact on the related properties. Besides, the imaginary parts of dielectric function of REs doped ZnO presented a red shift in low energy part, and the absorption spectra of which larger than that of pure ZnO. It was also found that the defects formation energies of REs doped ZnO on O-rich conditions were lower than that of on Zn-rich conditions, implying a more stable incorporation of REs on O-rich conditions. (C) 2014 Elsevier B.V. All rights reserved.