Thermal stability of gallium-doped zinc oxide thin film on glass substrates by an RF sputtering process.

The effects of a heat treatment on the structural and electrical properties of GZO thin films grown by RF magnetron sputtering were investigated. The heat treatment involved temperatures in the range from 200 degrees C to 500 degrees C under air. As the temperature was increased, the electrical properties of GZO thin films increased exponentially and the surface morphology was drastically altered. The effect of temperature is discussed based on electrical and structural characterization of the materials.

Enhanced and stable green emission of ZnO nanoparticles by surface segregation of Mg.

The effects of Mg addition on the emission of green photons from ZnO nanoparticles were studied. Energy dispersive x-ray spectroscopy (EDS) and Auger electron spectroscopy (AES) data demonstrated that ZnO nanoparticles with surface segregation of MgO (ZnO:MgO) were precipitated from colloidal reactions between Zn(2+),Mg(2+) and OH(-) ions suspended in ethanol. The photoluminescence emission spectra showed stronger green emission from suspended ZnO:MgO versus ZnO nanoparticles. ZnO:MgO also exhibited a stable green emission colour, which was slightly red-shifted from 495 to 520 nm with 168 days of ageing. It was postulated that the presence of MgO on the surface of ZnO prevented both the aggregation of ZnO nanoparticles via electrostatic stabilization of the suspension, and the formation of non-radiative recombination states on the surface, resulting in more intense, stable photoemission from ZnO. The red shift of the green emission from suspended ZnO nanoparticles with extended ageing was attributed to filling of radiative surface trap states in the bandgap.

Enhanced luminescence of SiO2:Eu3+ by energy transfer from ZnO nanoparticles.

ZnO nanoparticles embedded into SiO(2) by an ex situ method were shown to result in stable green emission with a peak at 510 nm compared to the normal peak at 495 nm from micron-sized ZnO powders. Green emission from ZnO nanoparticles was completely suppressed when they were embedded in SiO2 doped with Eu3+. Instead, the f-f emissions from Eu3+ were enhanced 5-10 times by energy transfer from the embedded ZnO nanoparticles to Eu3+. The Eu3+ luminescence increased as the Eu3+ concentration increased from 1 vs 5 mole % (for 10 mole % ZnO). In addition, the intensity increased as the embedded ZnO nanoparticles concentration increased up to 10 mole % (for 5 mole % Eu3+). The effects of phonon mediated energy transfer, quenching by activator interactions between Eu3+ ions, and energy back-transfer from Eu3+ ions to ZnO nanoparticles were discussed.