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High-quality Er:ZnO films were grown by the pulsed-laser deposition technique at high temperature followed by in situ annealing. The films demonstrate remarkable crystalline quality and array of self-assembled grains. Although the films show very low electrical resistivity (∼6.41×10-4 Ω cm) at room temperature, a semiconductor-metal transition was observed at 190 K for low doping in contrast to semiconductor behavior for high doping. The films show pronounced room temperature emission at 1.54 μm, illustrating the activation of Er3+ ions in ZnO matrix. Furthermore, no quenching effects in 1.54 μm emission characteristics were observed up to 2 wt % of Er doping in ZnO at room temperature. [ABSTRACT FROM AUTHOR]

We report on the observation of remarkable room-temperature ferromagnetism in nanocrystalline epitaxial Co:TiO2 films grown on sapphire (0001) substrates by a pulsed-laser deposition technique using high-density targets. The films were characterized by x-ray measurements, atomic force microscopy, micro-Raman, electron-paramagnetic resonance, and magnetization studies. The films exhibit three-dimensional islandlike growth that contains nanocrystalline particles. Our experimental results suggest that the remarkable ferromagnetism in Co:TiO2 films is controlled either by the interstitial Co2+ ions or small clusters, which are mainly present at the interface and on the surface of the films. Our work clearly indicates that Co interstitials and nanoclusters cause room-temperature ferromagnetism in Co-doped TiO2. [ABSTRACT FROM AUTHOR]