Photoluminescence and low-voltage cathodoluminescence characteristics of blue phosphor, ZnGa2O4:M (M = Na, Ag)

Photoluminescence and low-voltage cathodoluminescence characteristics of ZnGa₂O₄ phosphor doped with monovalent ions has been studied. Monovalent ions such as Na⁺ and Ag⁺ are incorporated into ZnGa₂O₄ lattices in order to increase the concentration of oxygen vacancies in the spinel lattice. By doping low concentrations of monovalent ions (Na⁺, Ag⁺) into ZnGa₂O₄, the self-activated blue luminescence originated from oxygen vacancies is enhanced. Also, the blue luminescence intensity is enhanced more along with a good color purity by annealing ZnGa₂O₄:Na⁺ in a reducing atmosphere, which is due to increasing the concentration of oxygen vacancies even more. The luminescence band at the UV region (λ_max=360 nm) does not become the major luminescence band by introducing Na⁺ ion into the ZnGa₂O₄ lattice, while the UV luminescence band becomes the major one by annealing the undoped ZnGa₂O₄ in a reducing atmosphere.     

Hydrothermal synthesis of hydrated vanadium oxide nanobelts using poly (ethylene oxide) as a template

With the aim of obtaining nanodevices as batteries, sensors and fuel cells, we prepared V₂O₅ and V₃O₇·H₂O nanobelts by a simple hydrothermal process using poly (ethylene oxide) (PEO) as a template. The yielding percentage of the nanomaterial is less in polymer-free V₂O₅ nanobelts and material size is also big. It is apparent that PEO used V₃O₇·H₂O form a continuous and relatively homogeneous matrix with a clearly 1–5 μm long and 50–150 nm diameter nanobelts morphology. The SEM micrographs suggest that there is no bulk deposition of polymer on the surface of the nano-crystallites. Strong interaction between the vanadyl group and the polymer during the formation process has been identified by the shifts of the vanadyl vibration peaks. The CV curve of the electrode made of the V₃O₇·H₂O nanobelts have higher current densities than the CV curve of the electrode made of V₂O₅ nanobelts.     

Enhanced PL and VUV absorption of BaZr(BO3)2:Eu3+ by Al3+ incorporation

Abstract— The photoluminescence (PL) and vacuum‐ultraviolet excitation (VUV) properties of BaZr(BO₃)₂ doped with the Eu³⁺ activator ion were studied as a new red phosphor for PDP applications. The excitation spectrum shows strong absorption in the VUV region with an absorption band edge at 200 nm. The charge‐transfer excitation band of Eu³⁺ was enhanced by co‐doping with an Al³⁺ ion into the BaZr(BO₃)₂ lattices. The PL spectrum shows the strongest emission at 615 nm, corresponding to the electric dipole ⁵D₀ → ⁷F₂ transition of Eu³⁺ in BaZr(BO₃)₂, which results in good red‐color purity.     

Characteristics and fabrication of nanohole array on InP semiconductor substrate using nanoporous alumina

Uniform arrays of nano-sized pore produced in porous alumina were transferred into InP substrates by inductively coupled plasma reactive ion etching (ICP-RIE). We observed a significant enhancement in the light output from InP substrate with nanohole arrays on the surface. Photoluminescence intensity of triangular arrays of air cylinders on InP substrate showed an enhancement up to 3 times compared with that from a raw InP substrate without such structure. The ICP-RIE technique using nanoporous alumina mask can be used as a prospective method in the fabrication of nanostructure materials for increasing the light output from semiconductor light emitting devices.     

Optimum IV-group ion concentrations in ZnGa2O4−xMx (M=S, Se, Te) phosphors for enhancement of luminescence

The ZnGa₂O_4−xM_x (M=S, Se, and Te ) samples with varying S, Se, and Te concentrations are synthesized through solid-state reactions. The X-ray diffraction patterns of ZnGa₂O_4−xM_x (M=S, Se, and Te) show that the positions of the (4 0 0) diffraction peak gradually shift to lower angles due to the doping of VI-group ions (S, Se, and Te) with larger ionic radius than oxygen. For ZnGa₂O_4−xS_x samples, the solubility limit is found to be about x=0.30. The cathodoluminescence measurements on ZnGa₂O_4−xM_x samples show that the optimized S, Se, and Te concentrations with the highest cathodoluminescence intensities are 0.10, 0.05, and 0.03, respectively. The luminous intensity of ZnGa₂O_3.95Se_0.05 is four times higher than that of ZnGa₂O₄. Thus, ZnGa₂O_3.95Se_0.05 can be a promising candidate phosphor for FED applications.