Search results for " Luminescence"

Oxygen-related defects and energy accumulation in aluminum nitride ceramics

2001

Abstract Features of oxygen-related defects in the AlN crystalline lattice were studied. Spectral characteristics of photoluminescence and photostimulated luminescence under the UV light irradiation of AlN ceramics were examined. The results obtained allow us to propose the mechanisms of luminescence and radiation-induced energy accumulation in AlN.

Iron-related luminescence centers in ZnWO 4 :Fe

2002

A systematic spectroscopic study of single ZnWO4 :Fe crystals with different iron concentrations has been performed under excitation by ultraviolet light, by synchrotron radiation or under photostimulation by near-infrared light. The luminescence of Fe3+-related centres has been studied. It is shown that iron centres of different types efficiently promote the formation of crystal defects at low temperatures. Electrons and holes can be trapped near Fe2+ or Fe3+ ions, which is further revealed in phosphorescence, thermostimulated or photostimulated luminescence. At room temperature the main effect of iron impurity is to reduce the light yield of a ZnWO4 scintillator.

Luminescence mechanisms of oxygen-related defects in AlN

2002

Spectral characteristics of native oxygen-related defects existing in the crystalline lattice of AlN were studied. Features of photoluminescence observed under exposure to ultraviolet light together with those of the photostimulated luminescence testify the recombination character of luminescence. The mechanism of luminescence of oxygen-related defects is proposed.

Optical storage in doped microstructures of alkali halides

2002

Peculiarities of colour centres production and their recombination in photostimulated processes in doped alkali halide microstructures were examined in connection with their practical use as active photostimulable media in miniaturised optoelectronic and photonic devices. The specific interaction of unrelaxed H-centres and electrons with the dopants in different valence and electronic states open a way for widening the scope of multifunctional (logical and mathematical) optical data processing and transfer.

Influence of the manufacturing process on the radiation sensitivity of fluorine-doped silica-based optical fibers

2011

International audience; In this work, we analyze the origins of the observed differences between the radiation sensitivities of fluorine-doped optical fibers made with different fabrication processes. We used several experimental techniques, coupling in situ radiation-induced absorption measurements with post mortem confocal microscopy luminescence measurements. Our data showed that the silica intrinsic defects are generated both from precursor sites and from strained regular Si-O-Si linkages. Our work also provides evidence for the preponderant role of the chlorine in determining the optical losses at about 3.5 eV. The results show that the manufacturing process of these fibers strongly af…

Doped Alkali Halide Thin Films as Active Media for Information Storage and Retrieval

1997

Recent progress in understanding the persistent luminescence in SrAl2O4:Eu,Dy

2019

This work was conducted with the funding of Scientific Research Project for Students and Young Researchers realised at the Institute of Solid State Physics, University of Latvia [SJZ/2018/2].

Luminescence properties of nonbridging oxygen hole centers at the silica surface

2009

Abstract Two variants of the surface-nonbridging oxygen hole center, ( Si–O)3Si–O• and ( Si–O)2(H–O)Si–O•, stabilized in porous films of silica nano-particles were investigated by time resolved luminescence excited in the visible and UV spectral range by a tunable laser system. Both defects emit a photoluminescence around 2.0 eV with an excitation spectrum evidencing two maxima at 2.0 and 4.8 eV, this emission decreases by a factor ∼2 on increasing the temperature from 8 up to 290 K. However, the different local structure influences the emission lineshape, the quantum yield and the decay lifetime. Such peculiarities are discussed on the basis of the symmetry properties of these defects.

Luminescence features of nonbridging oxygen hole centres in silica probed by site-selective excitation with tunable laser

2008

Time-resolved photoluminescence at 1.9 eV associated with the nonbridging oxygen hole centre (NBOHC) in silica was investigated under excitation with a ns pulsed laser system, tunable in the visible range. Mapping of the excitation/emission pattern evidences the site-selective excitation of the resonant zero phonon line (ZPL) transition due to its weak coupling with the stretching mode of dangling oxygen. Decay of ZPL follows an exponential law with lifetime of 15.3 μs, which provides a precise measure of the electronic transition probability of a single NBOHC.

Luminescence Efficiency of Si/SiO 2 Nanoparticles Produced by Laser Ablation

2019

Photoluminescence properties of Si(core)/SiO 2 (shell) nanoparticles produced by pulsed laser ablation in aqueous solution are investigated with the purpose to highlight the microscopic processes that govern the emission brightness and stability. Time resolved spectra evidence that these systems emit a µs decaying band centered around 1.95 eV, that is associated with the radiative recombination of quantum-confined excitons generated in the Si nanocrystalline core. Both the quantum efficiency and the stability of this emission are strongly dependent on the pH level of the solution, that is changed after the laser ablation is performed. They enhance in acid environment because of the H + pass…