Enhanced luminescence of europium in sol-gel derived BaTiO3/SiO2 multilayer cavity structure

We report on the sol-gel synthesis and optical properties of an Eu-doped multilayer structure consisting of a Bragg reflector/BaTiO3:Eu/Bragg reflector, with the Bragg reflector comprising of BaTiO3/SiO2 structures. Depending on the fabrication procedure two set of specimens were generated with Eu out of the cavity or Eu in the cavity. Enhanced Eu luminescence in the direction normal to the surface is observed for the most intense band 5D0 → 7F2 at 615 nm of trivalent europium in the cavity and correlates with anisotropy of the luminescence indicatrix, transmittance and reflection bands around 615 nm for the fabricated structure

The optical properties of multilayer periodic structures BaTiO3:Eu/SiO2

В работе представлены результаты исследования оптических свойств многослойных структур (брэгговских отражателей). Представлены спектры пропускания, отражения, люминесценции, возбуждения и кинетики люминесценции для брэгговских отражателей, сформированных на кварце с 6 и 12 чередующимися слоями BaTiO3:Eu/SiO2. Структуры демонстрируют фотонную запрещенную зону и ее смещение в длинноволновую область при увеличении числа пар слоев. В структурах наблюдается люминесценция европия с наиболее интенсивной полосой 615 нм. Обнаружено снижение интенсивности люминесценции европия при увеличении числа пар слоев в структуре. This paper presents the study of the optical properties of multilayer periodic structures, such as Bragg reflector, with different synthesis conditions. Transmission, reflection, luminescence, luminescence excitation spectra and kinetics of luminescence are presented for the Bragg reflectors formed on quartz with 6 and 12 alternating layers BaTiO3:Eu/SiO2. The structures demonstrate photonic band gap and its long wavelength shift with increasing number of layers. Europium luminescence with the most intensive band at 615 nm is observed from the structures. A decrease in the luminescence intensity with increasing the number of pairs of the layers in the structure is observed

ОПТИЧЕСКИЕ СВОЙСТВА МНОГОСЛОЙНЫХ ПЕРИОДИЧЕСКИХ СТРУКТУР BaTiO3: Eu/SiO2

This paper presents the study of the optical properties of multilayer periodic structures, such as Bragg reflector, with different synthesis conditions. Transmission, reflection, luminescence, luminescence excitation spectra and kinetics of luminescence are presented for the Bragg reflectors formed on quartz with 6 and 12 alternating layers BaTiO3:Eu/SiO2. The structures demonstrate photonic band gap and its long wavelength shift with increasing number of layers. Europium luminescence with the most intensive band at 615 nm is observed from the structures. A decrease in the luminescence intensity with increasing the number of pairs of the layers in the structure is observed.В работе представлены результаты исследования оптических свойств многослойных структур (брэгговских отражателей). Представлены спектры пропускания, отражения, люминесценции, возбуждения и кинетики люминесценции для брэгговских отражателей, сформированных на кварце с 6 и 12 чередующимися слоями BaTiO3:Eu/SiO2. Структуры демонстрируют фотонную запрещенную зону и ее смещение в длинноволновую область при увеличении числа пар слоев. В структурах наблюдается люминесценция европия с наиболее интенсивной полосой 615 нм. Обнаружено снижение интенсивности люминесценции европия при увеличении числа пар слоев в структуре

Optical Properties of Valve Metals Functional Thin Films Obtained by Electrochemical Anodization on Transparent Substrates

Nanostructured aluminum, tantalum, and vanadium oxide layers on glass substrates were obtained by electrochemical anodizing in oxalic and sulfuric–oxalic electrolytes. The morphological and optical properties of the obtained structures were investigated experimentally by scanning electron microscopy and transmission spectroscopy. Obtained oxide coatings are quasi-ordered arrays of vertical (aluminum oxide/tantalum oxide, aluminum oxide/vanadium oxide, and aluminum oxide obtained in the oxalic electrolyte) or non-ordered tree-like (aluminum oxide obtained in the sulfuric–oxalic electrolyte) pores depending on the initial film metal and anodizing technology. The light transmission in the range of 750–1200 nm is up to 60% for aluminum oxide/tantalum oxide/glass (annealed) and quasi-ordered aluminum oxide/glass structures, and around 40% for aluminum oxide/tantalum oxide/glass (not annealed) and aluminum oxide/vanadium oxide. Non-ordered aluminum oxide is characterized by low transmission (no more than 8%) but has a developed surface and may be of interest for the formation of films with poor adhesion on smooth substrates, for example, photocatalytic active xerogels. The refractive indices of dispersion of the obtained layers were calculated from the transmission spectra by the envelope method. The dispersion of the refractive indices of the obtained oxide films is insignificant in a wide range of wavelengths, and the deviation from the average value is assumed to be observed near the intrinsic absorption edges of the films. The glasses with proposed semi-transparent nanostructured oxide layers are promising substrate structures for subsequent sol–gel coating layers used in photocatalytic purification systems or up-conversion modules of tandem silica solar cells with forward and reverse illumination

Europium luminescence from amorphous yttrium alumina films on fused silica substrates

In this work, we investigate photoluminescence of sol-gel derived films corresponding to yttrium alumina garnet Y3Al5O12 doped with trivalent europium. The films with three concentrations of europium 0,02; 0,025; 0,03 M with the thickness 210-220 nm were deposited on fused silica substrates by the corresponding sols’ spinning followed by drying and high temperature annealing at 1000 °С for 30 min. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive Х-ray (EDX) analysis as well as ellipsometry, photoluminescence (PL) and photoluminescence excitation spectroscopy (PLE). All of the fabricated samples were amorphous and revealed room-temperature luminescence bands within the range of 550 – 750 nm corresponding to 5D0 → 7Fj (j=0,..,4) transitions of trivalent europium ions with the most intensive bands at 610 – 630 nm and 680 – 710 nm. The intensity of europium luminescence increases with europium concentration. The photoluminescence excitation spectra measured at the emission wavelength 710 nm exhibit strong bands at 220 nm, which could be associated with absorption of exciting light within Eu3+ - O2-bands. Practical application of the obtained films transforming ultraviolet irradiation into visible is discussed

Optical properties of multilayer BaTiO3/SiO2 film structures formed by the sol–gel method

Multi-layer film structures BaTiO3/SiO2 with a thickness of ~1 μm containing up to 14 pairs of layers were synthesized by the sol–gel method with sequential heat treatment. It is shown that the synthesized structures are X-ray amorphous. The formation of bands in the transmission and reflection spectra caused by interference effects is demonstrated. A more regular structure exhibits a photon band gap (opacity band) in the visible range with main minimum at 636 nm and corresponding maximum in the reflection spectra. Dispersion characteristics of barium titanate films with different concentrations of initial sols were studied and an increase in the refractive index with an increase in the concentration of sol was demonstrated. For a sol with a concentration of 60 mg/ml, the refractive index in the spectral range of 390–1600 nm is 1.88–1.81. The prospects of sol–gel technology for the formation of BaTiO3/SiO2 structures for nanophotonics and solar radiation converters are discussed

Sol–Gel Fabrication and Luminescence Properties of Multilayer Eu-Doped BaTiO3–SiO2 Xerogel Nanostructures

With the use of sol–gel method BaTiO3–SiO2 multilayer structures were fabricated on glass or fused silica substrates employing dipping or spinning procedure. The photonic stop band was observed in the reflection and transmission spectra of the multilayer structure annealed at 450∘C. It is redshifted with an increase of the thicknesses of BaTiO3 and SiO2 layers. For structures comprising Eu-doped BaTiO3 layers of different thicknesses photoluminescence with the main band at 614nm was detected. It is characterized with the double-exponential decay with the lifetimes of about 0.5ms and 1.1ms which do not depend significantly on the photonic stop band position

Optical Properties and Upconversion Luminescence of BaTiO3 Xerogel Structures Doped with Erbium and Ytterbium

Erbium upconversion (UC) photoluminescence (PL) from sol-gel derived barium titanate (BaTiO3:Er) xerogel structures fabricated on silicon, glass or fused silica substrates has been studied. The fabricated structures under continuous-wave excitation at 980 nm and nanosecond laser excitation at 980 and 1540 nm demonstrate room temperature PL with the bands at 410, 523, 546, 658, 800 and 830 nm, which correspond to the 2H9/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, 4F9/2→ 4I15/2 and 4I9/2→ 4I15/2 transitions in Er3+ ions. The intensity of erbium UС PL increases when an additional macroporous layer of strontium titanate is used beneath the BaTiO3 xerogel layer. It is enhanced for BaTiO3 xerogel films codoped with erbium and ytterbium (BaTiO3:Er,Yb). The redistribution of the intensity of the PL bands is observed for the latter and it depends on the excitation conditions. Finally, a Bragg reflector and a microcavity structure comprising of alternating (BaTiO3:Er,Yb) and SiO2 xerogel layers were fabricated with the cavity mode near the red PL band of Er3+ ions. Enhancement of UC PL from the microcavity was observed for the sample annealed from 450°C to 600°C. The fabricated cavity structures annealed at 450°C allow us to tune the cavity mode with 10 nm shift within the temperature range from +20°C to +130°C. Photonic application of BaTiO3 xerogel structures doped with lanthanides is discussed

ЗОЛЬ-ГЕЛЬ СИНТЕЗ И ПРОПУСКАНИЕ МНОГОСЛОЙНЫХ ПОКРЫТИЙ BaTiO3/SiO2

SOL-GEL METHOD, BARIUM TITANATE, FILTER.В работе изложены результаты формирования золь-гель методом многослойных покрытий, отличающихся показателем преломления BaTiO3/SiO2, на кварцевых и кремниевых подложках. Показано, что многослойные покрытия после термообработки при температуре 450 ºС формируют полосу непрозрачности на спектре пропускания с минимумом 693 нм для 14 пар слоев BaTiO3/SiO2, уменьшая пропускание до 35 %, при этом пропускание в ИК-диапазоне 1000-2000 нм ослабляется до 70-75 %. Пленки являются рентгеноаморфными после термообработки при температурах 450 и 600 ºС. Обсуждается перспектива применения разрабатываемых фильтров для оптики и нанофотоники

ОПТИЧЕСКИЕ СВОЙСТВА ТОНКИХ ПЛЕНОК ZnO+10 % ITO НА ПОДЛОЖКАХ АНОДНОГО ОКСИДА АЛЮМИНИЯ

ZnO thin films of zinc oxide doped with 10 % ITO (indium tin oxide) on anodic aluminum oxide substrates are formed in vacuum during high-frequency repetitively pulsed laser deposition. The morphology of films on porous and non-porous surfaces of substrates was studied by atomic force microscopy. The optical properties of the films in the visible, near, and middle IR regions of the electromagnetic radiation spectrum, the Raman spectra, and also the features of the photoluminescence characteristics have been experimentally investigated. Zinc oxide films can be used in optoelectronic transducers, as luminescent material, in the form of transparent electrodes, sensitive layers of gas and biological sensors, catalysts, X-ray and gamma-radiation detectors.Тонкие пленки оксида цинка ZnO, легированные 10 % ITO (оксидом индия-олова), на подложках из анодного оксида алюминия сформированы в вакууме при высокочастотном импульснопериодическом лазерном осаждении. Методом атомно-силовой микроскопии изучены морфологии пленок на пористой и беспористой поверхностях подложек. Экспериментально исследованы оптические свойства пленок в видимой, ближней и средней инфракрасных областях спектра электромагнитного излучения, спектры комбинационного рассеяния, а также особенности фотолюминесцентных характеристик. Пленки оксида цинка могут быть использованы в оптоэлектронных преобразователях как люминесцентный материал, в виде прозрачных электродов, чувствительных слоев газовых и биологических сенсоров, катализаторов, детекторов рентгеновского и гамма-излучений