Influence of doping rate in Er3+:ZnO films on emission characteristics

Synchrotron-based VUV excitation-induced ultrahigh quality cool white light luminescence from Sm-doped ZnO

We report that the rare-earth (RE) ion, Sm-doped ZnO, acts as white light emitting vacuum ultraviolet (VUV) phosphors and possesses an ultrahigh color rendering index (CRI) and color quality scale (CQS). The VUV-excited emission spectra measured from the synchrotron source reveal the emergence of multi-color emission bands in the visible-IR region and substantially depend on the concentration of Sm³⁺ ions. A mechanism is proposed to elucidate the origin behind the high-energy bandgap excitation of the host charge carrier and subsequent energy transfer to the Sm³⁺ states leading to additional green-yellow-orange emission bands of Sm³⁺(⁴G_5/2→⁶H_J(J=5/2,7/2,and9/2)). High-quality cool white light (correlated color temperature 5600 K) having CIE coordinates (0.33, 0.35) with a CRI as high as 95.89 and a CQS value of 94.49 is achieved for Zn_0.985Sm_0.015O under synchrotron VUV radiations. This Letter demonstrates that RE activated ZnO-based phosphors are expected to be a promising candidate in solid state lighting, as well as plasma display devices.

Effect of Ge Nanocrystals on 1.54 μm Photoluminescence Enhancement in Er₂O₃:ZnO and Ge Co-Sputtered Films

Photoluminescence (PL) of Er and Ge co-doped ZnO films synthesized by radio frequency magnetron co-sputtering was investigated. X-ray diffraction (XRD) patterns showed that the annealing process at 400–800 °C led to the formation of nanocrystal (nc) Ge. Samples containing nc-Ge showed a strong visible PL with a peak at 582–593 nm, which was consistent with the calculated energy of the exciton of the ~5 nm-sized nc-Ge, according to the quantum confinement effect. The formation of nc-Ge could greatly enhance the 1.54 μm emission, and it is considered that the 1.54 μm PL enhancement may come from a joint effect of both the energy transfer from nc-Ge to Er³⁺ and the local environment change of Er³⁺.

Near-infrared luminescence of Nd3+ and Tm3+ ions doped ZnO nanocrystals

Intense near-infrared luminescence of Nd(3+) and Tm(3+) ions in the region of 860-1550 nm were achieved in 10-15 nm wurtzite ZnO nanocrystals fabricated by a facile sol-gel process. The optical properties of Nd(3+) and Tm(3+) ions were investigated by using the steady-state and time-resolved laser spectroscopy. Due to the well-ordered crystal-field surroundings experienced by Nd(3+) and Tm(3+) ions, sharp and well resolved emission lines of Nd(3+) and Tm(3+) ions were identified at 4-300 K. Time-resolved luminescence and decay behaviors of the (4)F(3/2)-->(4)I(11/2) transition of Nd(3+) ions reveal the existence of multiple Nd(3+) sites in ZnO nanocrystals.