Synthesis, Characterization and Optical Properties of ZnO Nanoparticles Doped with Er and Yb

This paper discusses the structure, particle morphology, and optical properties of un-doped ZnO and ZnO doped with Er3+ and Yb3+ lanthanide ion nanoparticles (NPs) through a process denominated sol-gel-hydrothermal. According to the pattern of X-ray diffraction, ZnO:Er and ZnO:Yb is formed by a single-phase wurtzite structure with crystallites sized ~65 nm on average, and Er or Yb dopant ions in the hexagonal structure of ZnO, specifically in its distorted lattice sites. The results also suggest the possible role of oxygen vacancies or Ox– (defects) in the energy transfer from ZnO to the Er or Yb ions with a decrease of 3.18 eV and 3.19 eV in bandgap values to a red shift.

Ferromagnetic Homogeneous Polycrystalline Zn1-xCoxO Oxides

In this work, the structural and magnetic properties of polycrystalline Zn1-xCoxO (x = 0, 0.02, 0.05, 0.0625, 0.10 and 0.15) oxides were studied in detail. Rietveld refinement of x-ray diffraction spectra indicates that a single-phase wurtzite structure was formed in Zn1-xCoxO samples for x up to 0.10. The magnetization for x = 0.02 can be fitted to a model with a paramagnetic Curie term and a diamagnetic constant which could arise from spins of isolated free Co ions and a diamagnetic background, respectively. For x > 0.02, however, an additional antiferromagnetic Curie-Weiss term needs to employ for fitting. This is due to an additional contribution from clustered Co ions that are in nearest neighbor positions through oxygen ions. Results show that the substitution of Co at the Zn site does not occur in a completely random manner but Co ions appear to have a tendency for clustering. In addition, the homogenous ZnO:Co thin film prepared by Pulsed Laser Deposition on SiO2/Si substrate shows ferromagnetic behavior at room temperature.