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High Efficient Vacuum Ultraviolet-Excitable SrSi <sub/>2</sub> N <sub/>2</sub> O <sub/>2</sub> :Eu <sup>2+</sup> Green-Emitting Phosphors Synthesized via Different Pressures
摘要： The luminescence properties of Eu2+-activated SrSi2N2O2 phosphor under VUV excitation have been firstly studied in this work. Normal pressure (1 atm) and high pressure (5 atm) synthesized-Sr0.96Si2N2O2:Eu2+0.04 powders were prepared by solid state reaction at temperature between 1400 °C and 1600 °C under 5% H2–95% N2 atmosphere and 5 atm N2 atmosphere, respectively. XRD patterns show that the purity and crystallinity of 1 atm-Sr0.96Si2N2O2:Eu2+0.04 is better than that of 5-atm Sr0.96Si2N2O2:Eu2+0.04. Green emission broad band at 541 nm with Full Width at Half Maximum (FWHM) of 75 nm can be efficiently excited under 172 nm. The luminescent intensity of 1 atm-Sr0.96Si2N2O2:Eu2+0.04 is almost two folds than that of 5-atm Sr0.96Si2N2O2:Eu2+0.04. Moreover, photoluminescent spectra of Sr0.96Si2N2O2:Eu2+0.04 with 10 K to 300 K were also carried out in this study. SrSi2N2O2:Eu2+ phosphor is a new and promising green phosphor for VUV applications.
关键词： Oxynitride,VUV,SrSi2N2O2,Photoluminescence,Phosphors
更新于2025-09-19 17:15:36
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Tailoring Photoluminescence from Si-Based Nanocrystals Prepared by Pulsed Laser Ablation in He-N2 Gas Mixtures
摘要： Using methods of pulsed laser ablation from a silicon target in helium (He)-nitrogen (N2) gas mixtures maintained at reduced pressures (0.5–5 Torr), we fabricated substrate-supported silicon (Si) nanocrystal-based ?lms exhibiting a strong photoluminescence (PL) emission, which depended on the He/N2 ratio. We show that, in the case of ablation in pure He gas, Si nanocrystals exhibit PL bands centered in the “red - near infrared” (maximum at 760 nm) and “green” (centered at 550 nm) spectral regions, which can be attributed to quantum-con?ned excitonic states in small Si nanocrystals and to local electronic states in amorphous silicon suboxide (a-SiOx) coating, respectively, while the addition of N2 leads to the generation of an intense “green-yellow” PL band centered at 580 nm. The origin of the latter band is attributed to a radiative recombination in amorphous oxynitride (a-SiNxOy) coating of Si nanocrystals. PL transients of Si nanocrystals with SiOx and a-SiNxOy coatings demonstrate nonexponential decays in the micro- and submicrosecond time scales with rates depending on nitrogen content in the mixture. After milling by ultrasound and dispersing in water, Si nanocrystals can be used as e?cient non-toxic markers for bioimaging, while the observed spectral tailoring e?ect makes possible an adjustment of the PL emission of such markers to a concrete bioimaging task.
关键词： pulsed laser ablation in gases,pulsed laser deposition,silicon quantum dots,bioimaging,silicon nanoparticles,quantum con?nement,photoluminescence,silicon oxynitride
更新于2025-09-19 17:13:59
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Study of optical and structural properties of sputtered aluminum nitride films with controlled oxygen content to fabricate Distributed Bragg Reflectors for ultraviolet A
摘要： Aluminum nitride (AlN) films with controlled oxygen content were deposited on silicon substrates, and optical properties studied with dependency on film morphology. Combinations of argon (Ar) and nitrogen (N2) gases were used in RF magnetron sputtering of an AlN target. The resulting refractive index ranging from 1.6 to 2.0 at 400 nm was tuned by controlling the sputter gas flow rate ratio of Ar and N2. The resulting refractive index is associated with density and aluminum nitride content of the thin films. Distributed Bragg Reflectors (DBRs) optimized for ultraviolet-A reflectivity were fabricated with pairs of alternating AlN thin films using an explicit combination of low-n and high-n to further investigate the thin film optical properties. The effect of structural transformation in the DBR stack on the progress of optical properties was studied. The DBRs exhibit a negligible extinction coefficient, utilizing precise control of oxygen incorporation with one sputtering target.
关键词： Optical properties,Materials interface,Aluminum oxynitride,Aluminum nitride,AlN,Refractive index,DBR,Magnetron sputtering
更新于2025-09-16 10:30:52
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Chemical and structural heterogeneities in Nd-doped oxynitride phosphate laser glasses
摘要： The application of oxynitride glasses in optics has been limited due the issues inherent in their preparation that result in bubbles, metallic inclusions or opacity. Although the synthesis of oxynitride phosphates is easier than in silicates, due to their lower melt viscosity, the remaining water in the form of OH causes, for instance, the neodymium luminescence to be negatively affected. We report on the preparation of oxynitride Nd phosphate glasses that are submitted first to a dehydroxylation, so that their structure and properties can be studied as a function of the nitrogen content taking a completely homogeneous OH-free glass as the starting point of each synthesis. Raman and Brillouin Spectroscopy confirmed the segregation in oxide and N-enriched regions, and NMR of the glasses has been used to calculate the O/P ratio from the distribution of P(O,N)4 groups. The difference between this and the experimental one obtained from the elemental analyses confirms the segregation in oxide and oxynitride regions that is produced during the ammonolysis of the phosphate glass. The oxynitride glass network could thus be considered a non-homogeneous mixture of the oxide and the nitrided phases that are segregated due to the non-randomness of the nitridation reaction.
关键词： Nitridation,Phosphate glasses,Laser glasses,Oxynitride glasses,Water
更新于2025-09-12 10:27:22
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An exciting boost for solar cells
摘要： A process called singlet fission has the potential to enhance the efficiency of solar cells. The mechanism has been difficult to implement in such devices, but experiments demonstrate a way forward.
关键词： efficiency,hafnium oxynitride,tetracene,solar cells,silicon solar cells,singlet fission
更新于2025-09-11 14:15:04
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[IEEE 2018 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Campinas (2018.10.8-2018.10.10)] 2018 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Study of the fabrication of pedestal based-optical waveguides for applications in nonlinear optics
摘要： In this work we present the details regarding the fabrication process of pedestal based optical waveguides, using different materials with large optical nonlinearities as core layer. With the pedestal fabrication process it is possible to use novel materials that are highly inert to chemical etchants or alloys composed of heavy metal elements, since this technique does not require etching of the core material itself. Lateral confinement of light is performed through the fabrication of pedestals by Reactive Ion Etching (RIE) on the lower cladding. The last step in the fabrication process is the deposition of the core layer and, for this reason, etching this layer is no longer necessary. The materials used as core layer are Aluminum Nitride and Titanium oxynitride films, due to the fact that these materials present a great potential for the fabrication of Nonlinear Optics integrated devices.
关键词： nonlinear optics,aluminum nitride,Pedestal waveguide,titanium oxynitride
更新于2025-09-11 14:15:04
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Correlation between composition, microstructure, and emission properties in Nd-doped Si-rich Si oxynitride films: investigation into the nature of the sensitizer
摘要： Rare earth (RE) ions doped in Si-based materials, compatible with Si technology, are promising compounds with regards to optical communication and energy conversion. In this article, we show the emission properties of Nd-doped Si-rich Si oxynitride (Nd-SRSON) ?lms, and their dependence on the dangling bond density and the nature of the sensitizer. These ?lms were prepared by reactive magnetron sputtering and post-annealing. The ?lm composition, microstructure, and emission properties were investigated as a function of deposition parameters and annealing temperatures. Both Fourier transform infrared (FTIR) and ellipsometry spectroscopy measurements have con?rmed that the sample composition (Si/N ratio) can be carefully tuned by varying the ratio of reactive nitrogen to argon in the sputtering plasma. Moreover, FTIR and x-ray photoelectron spectroscopy measurements demonstrate the existence of both nitrogen and oxygen dangling bonds (N? and O?) in as-deposited samples. These dangling bonds were passivated during annealing. Under non-resonant excitation at 488 nm, the ?lms exhibit a signi?cant photoluminescence (PL) signal from Nd3+ ions demonstrating the occurrence of an effective sensitization of Nd3+ ions in the host matrix. Both PL excitation and ellipsometry results (the energy band gap from new amorphous model) exclude the sensitization by an exciton with energy over the band gap, whereas the presence of Si agglomerates, at the atomic scale, have been identi?ed as effective sensitizers towards Nd3+ ions. This work not only provides knowledge to optimize Si-based materials for favorable emission properties, but also, presents a universal methodology to investigate the nature of sensitizers for RE emitters. This allows one to ?nd correlations between composition, microstructure, and emission properties.
关键词： photoluminescence,rare earth,neodymium,non-resonant excitation,thin ?lm,Si-rich Si oxynitride
更新于2025-09-10 09:29:36
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Structural Change in SrSiO <sub/>3</sub> Induced by Introduction of Nitrogen
摘要： SrSiO313xN2x with a single chain inosilicate structure, which has not been realized in Sr and Sr-rich metasilicates, has been synthesized by introduction of a small amount of nitrogen into SrSiO3. Its crystal structure was determined by a single-crystal X-ray analysis. Anion sites are severely distorted along b-axis, resulting in formation of the inosilicate structure. The present material activated with Eu2+ exhibits red emission under near ultraviolet and visible light irradiation. Our results suggest a new strategy for development of novel oxynitrides.
关键词： Phosphor,New compound,Oxynitride
更新于2025-09-10 09:29:36
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Enhanced surface passivation of predictable quantum efficient detectors by silicon nitride and silicon oxynitride/silicon nitride stack
摘要： In this paper, we investigate three different passivating films for use in predictable quantum efficient detectors: two monolayer films of SiNx with different compositions and one double-layer stack of SiNxOy capped with SiNx, all deposited on very high resistivity silicon substrates. In addition to the conventional characterization methods, we also utilize the novel method of photoluminescence imaging under applied bias (PL-V) and high voltage soaking to modulate the fixed charge density Qf in the layers. All films exhibit very good passivating properties after deposition and annealing, with the oxynitride stack providing the best passivation, resulting in an effective carrier lifetime close to 20 ms. This value is explained by a relatively high fixed charge density of Qf = 1.12 × 1012 cm?2 and low interface defect density (S0,n = 6.0 × 102 cm/s), giving a chemical passivation which is an order of magnitude better than the investigated nitrides. Both nitride films were readily charged by voltage soaking, increasing the effective carrier lifetime by about 20%. Based on the passivating properties, photodetector device simulations predict that self-induced photodiodes made with any of these passivation layers will have an internal quantum deficiency well below 1 ppm for selected wavelengths at room temperature, and all the investigated materials are thus good candidates for use as passivating layers in such photodiodes.
关键词： photoluminescence imaging,surface passivation,silicon nitride,high voltage soaking,predictable quantum efficient detectors,silicon oxynitride
更新于2025-09-09 09:28:46
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Optimizing the Synthesis of Zinc-rich Gallium Zinc Oxynitrides by Combining Co-Precipitation and Moisture-Assisted Nitridation
摘要： ZnO-co-doped GaN is a promising catalyst for photocatalytic overall water splitting in the visible light range. The conventional high-temperature synthesis has the drawback that only low amounts of Zn2+ ions can be incorporated into the GaN:ZnO matrix due to a substantial loss of volatile Zn metal during the nitridation of the binary oxides in flowing NH3. By applying moisture-assisted nitridation of a co-precipitated GaZn precursor under milder conditions it was possible to significantly reduce the Zn loss during nitridation. Using a GaZn precursor with a high Zn content, GaN:ZnO nanoparticles containing high amounts of Zn were obtained. The bandgap was found to decrease nearly linearly with increasing Zn content. Concomitantly, the defect density and structural disorder increased with increasing Zn content.
关键词： Gallium zinc oxynitride,UV/Vis spectroscopy,Co-precipitation,Nitridation,Raman spectroscopy
更新于2025-09-04 15:30:14