87 research outputs found
YAG nano-light sources with high Ce concentration
We investigate the luminescence properties of 10 nm YAG nanoparticles doped
with Ce ions at 0.2%, 4% and 13% that are designed as active probes for
Scanning Near field Optical Microscopy. They are produced by a physical method
without any subsequent treatment, which is imposed by the desired application.
The structural analysis reveals the amorphous nature of the particles, which we
relate to some compositional defect as indicated by the elemental analysis. The
optimum emission is obtained with a doping level of 4%. The emission of the YAG
nanoparticles doped at 0.2% is strongly perturbed by the crystalline disorder
whereas the 13% doped particles hardly exhibit any luminescence. In the latter
case, the presence of Ce4+ ions is confirmed, indicating that the Ce
concentration is too high to be incorporated efficiently in YAG nanoparticles
in the trivalent state. By a unique procedure combining cathodoluminescence and
Rutherford backscattering spectrometry, we demonstrate that the enhancement of
the particles luminescence yield is not proportional to the doping
concentration, the emission enhancement being larger than the Ce concentration
increase. Time-resolved photoluminescence reveals the presence of quenching
centres likely related to the crystalline disorder as well as the presence of
two distinct Ce ions populations. Eventually, nano-cathodoluminescence
indicates that the emission and therefore the distribution of the doping Ce
ions and of the defects are homogeneous
Fluorescent oxide nanoparticles adapted to active tips for near-field optics
We present a new kind of fluorescent oxide nanoparticles with properties well
suited to active-tip based near-field optics. These particles with an average
diameter in the range 5-10 nm are produced by Low Energy Cluster Beam
Deposition (LECBD) from a YAG:Ce3+ target. They are studied by transmission
electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), classical
photoluminescence, cathodoluminescence and near-field scanning optical
microscopy (NSOM). Particles of extreme photo-stability as small as 10 nm in
size are observed. These emitters are validated as building blocks of active
NSOM tips by coating a standard optical tip with a 10 nm thick layer of
YAG:Ce3+ particles directly in the LECBD reactor and by subsequently performing
NSOM imaging of test surfaces.Comment: Changes made following Referee's comments; added references; one
added figure. See story on this article at:
http://nanotechweb.org/cws/article/tech/3606
Tunable mid IR plasmon in GZO nanocrystals
International audienceDegenerate metal oxide nanoparticles are promising systems to expand the significant achievements of plasmonics into the infrared (IR) range. Among the possible candidates, Ga-doped ZnO nanocrystals are particularly suited for mid IR, considering their wide range of possible doping level and thus of plasmon tuning. In the present work, we report on the tunable mid IR plasmon induced in degenerate Ga-doped ZnO nanocrystals. The nanocrystals are produced by a plasma expansion and exhibit unprotected surfaces. Tuning the Ga concentration allows tuning the localized surface plasmon resonance. Moreover, the plasmon resonance is characterized by a large damping. By comparing the plasmon of nanocrystals assemblies to that of nanoparticles dispersed in an alumina matrix, we investigate the possible origins of such damping. We demonstrate that it partially results from the self-organization of the naked particles but also from intrinsic inhomogeneity of dopants
Visible luminescence improvement of ZnO/PAA nano-hybrids by silica coating
International audienceThe effect of a silica coating on the improvement of the visible light emission properties of ZnO/polyacrylic acid (PAA) nanohybrids is reported. The synthesized material consists of ZnO nanocrystals incorporated into the PAA mesospheres and then coated with silica. The silica amount can be controlled by the concentration of ammonia used in the sol-gel process as catalyst. The interaction between PAA and ammonia is crucial, the presence of the former tending to inhibit the catalytic action of the latter. We show that there is an optimum in the silica amount around the mesospheres, which leads to a drastic increase in the defect-related visible photoluminescence quantum yield of ZnO nanocrystals. A six-fold increase of the quantum yield can thus be achieved, reaching competitive values higher than 60%. This optimum is a compromise between a complete protective silica layer around the mesospheres and too thick a layer inducing inefficient absorption of excitation light by the coating
Fabrication and characterization of organic semiconductor-based microcavities
International audienc
Numerical model for injection and transport in multilayers OLEDs
International audienceWe present a recently developed numerical code for OLED simulation. This code contains a detailed description of contacts, charge transport and recombination. Its efficiency is briefly shown through examples of single- and bilayer devices and discussed in more detail through the investigation of the action of a LiF thin film on injection. In particular, we show how the code can help to discriminate between several possible explanations for this phenomeno
Effect of the quantum confinement on the luminescent properties of sesquioxides
International audienc
ZnO nanoparticles as a luminescent down-shifting layer for photosensitive devices
International audienc
Photoluminescence de microcavités organiques à base d'oligomères de phénylène vinylène et mise en évidence de l'influence de la structure de la cavité sur l'émission de l'Alq
Les effets du vieillissement thermique sur les films PANI-CSA ont été étudiés sur la conductivité et la structure cristallographique. Avec le vieillissement, le maximum de conductivité se déplace
vers les hautes températures et le comportement quasi-métallique disparaît. Cependant une fraction cristalline de 16
préliminaire des résultats est effectuée avec un modèle simple dans lequel la résistivité se compose d'un terme métallique et d'un terme de hopping en série
Sol-gel processing of hybrid ZnO nanophosphors self-assembled in mesospheres for WLED application.
International audienc
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