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.

Pulsed-Metal Organic Chemical Vapor Deposition (PMOCVD) for Growth of Single Phase Wurtzite MgxZn1-xO Epitaxial Film with High Mg Content (x=0.51)

ABSTRACTPulsed metal organic chemical vapor deposition (PMOCVD) was used to grow high Mg content, high quality, wurtzite MgxZn1-xO (MgZnO) epitaxial film to realize photodetectors and emitters in the solar blind spectral window. MgZnO films with various Mg contents were deposited on c-plane Al2O3 with and without AlN buffer layer. The band gap of the films range from 3.24 eV to 4.49 eV, corresponding to fraction of Mg between x=0.0 to x=0.51, as determined by Rutherford backscattering spectroscopy (RBS). Cathodoluminescence (CL) measurement showed a linear blue shift in the spectral peak position of MgxZn1-xO with an increase in x. No multi-absorption edge or CL band splitting was observed, indicating the phase purity of the films and was confirmed by XRD analysis. The surface quality of the films has improved with the increase in Mg content. To the best of our knowledge, the current result shows the highest Mg content (x=0.51), high quality, single phase wurtzite MgZnO epitaxial film ever grown by MOCVD. This is realized due to the non-equilibrium behavior of PMOCVD in which radicals that are formed during the growth process will have insufficient time to reach equilibrium.

Raman scattering and interstitial Li defects induced polarization in co-doped multiferroic Zn0.96-yCo0.04LiyO (0.00 ≤ y ≤ 0.10) nanoparticles

Structural and Raman analysis confirmed a single phase wurtzite hexagonal crystalline structure of Li–Co co-doped ZnO nanoparticles.

Photoluminescence of ZrO2-ZnO Hybrid Nanotube Arrays Produced by Electrodeposition

Highly ordered ZrO2 nanotube (NT) arrays were fabricated by anodization in organic electrolyte containing NH4F. The NTs have an opened porous structure at the top end. A facile electro-deposition technique was used to prepare ZnO quantum dots (QDs) in the pores of the ZrO2 NTs. Characterizations of SEM, XRD, HR-TEM were performed on the NTs. The results confirmed the formation of single-phase wurtzite ZnO nanoparticles in the ZrO2 NTs with a size around 20 nm. Photoluminescence (PL) spectra proved that the ZnO QDs coating had strongly enhanced the PL signal for blue (366nm) and green (503nm) light emissions of the hybrid NT arrays. That maybe arose from structure-dependent defects and oxygen vacancy in the hybrid layers.

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.