Eu-doped ZnO nanoparticles prepared by the combustion reaction method: Structural, photoluminescence and dielectric characterization

• Published in: Materials science in semiconductor processing 2015-02, Vol.30, p.135-141
• Main Authors: Pessoni, H.V.S., Maia, L.J.Q, Franco, A.
• Format: Article
• Language: English
• Subjects: Bandgap energy; Combustion; Combustion reaction; Crystal defects; Doping; Energy transfer; Eu-doped ZnO; Nanoparticles; Photoluminescence; Semiconductors; Zinc oxide
• ISSN: 1369-8001; 1873-4081
• DOI: 10.1016/j.mssp.2014.09.039

In the present study, we report the structural, photoluminescence (PL) and dielectric characterization of nanoparticles of Eu-doped ZnO (Zn1−xEuxO) with x = 0, 0.01, 0.02 and 0.03 at %Eu. The samples were synthesized by the combustion reaction method and characterized by X-ray diffraction (XRD), and transmission electron microscope (TEM). The XRD patterns of all samples exhibited sharp and intensive peaks of hexagonal wurtzite structure of ZnO without any evidence of spurious crystalline phases, except for x=0.03 that exhibits small peak corresponding to Eu2O3 phase. The nanoparticles crystalized in roughly spherical morphology and the particle size decreased with the Eu doping concentration, being ~28nm and ~17nm for undoped ZnO and x=0.03, respectively. The photoluminescence emission spectrum of Eu-doped ZnO nanoparticles exhibited three intense band emissions at 578, 590 and 612nm which were attributed to 5D0→7F0, 5D0→7F1 and 5D0→7F2 transitions of Eu3+ ions when excited with 394nm wavelength, originated from intra- 4f transition of Eu3+ ions, respectively. The PL intensity lifetime exhibited two decay profiles that increased with Eu3+ ions concentration. The bandgap energy Eg, and dielectric constant ε, increased with Eu doping concentration; being ~3.25, ~3.25 and ~3.26eV, and ~6.32, ~7.70 and ~10.37 for x=0.01, 0.02 and 0.03, respectively. These results were discussed in terms of the defects present in the surface and/or subsurface of the nanoparticles. An energy transfer mechanism is proposed, which involve energy transferred from ZnO host to Eu3+ ions through defects states of ZnO in Eu-doped ZnO nanoparticles. A possible energy transfer process was explained in a schematic cartoon labeling the energy levels of Eu3+ ions in the Eu-doped ZnO nanoparticles.