Search results for "Spectral"
showing 10 items of 3116 documents
Luminescence properties of Eu, RE3+ (RE = Dy, Sm, Tb) co-doped oxyfluoride glasses and glass–ceramics
2017
Abstract Eu, RE3+ (RE = Dy, Sm, Tb) co-doped SiO2–CaF2–Al2O3–CaO oxyfluoride glasses have been prepared by the melt quenching method. By heating the precursor glasses at 670 °C for 1 h, glass–ceramics containing CaF2 nanocrystallites were obtained. DTA and XRD measurements were performed. Excitation spectra of the prepared samples as well as photoluminescence spectra at the excitation of 355 nm and 450 nm were measured, CIE colour coordinates and colour rendering indexes were found. In the glass–ceramics the presence of Eu2+ ions was observed by a broad emission band in the 400–500 nm spectral range. The most promising doping combinations for white light luminophores within our research are…
Excitation and photoluminescence spectra of single- and non-single-phased phosphors based on LaInO3 doped with Dy3+, Ho3+ activators and Sb3+ probabl…
2017
Abstract Single-phased La 0.95 Ln 0.05 InO 3 ( Ln – Dy, Ho), La 0.90 Dy 0.05 Ho 0.05 InO 3 , LaInO 3 ceramic samples as well as the La 0.95 Ln 0.05 In 0.98 Sb 0.02 O 3 ( Ln – Dy, Ho), La 0.90 Dy 0.05 Ho 0.05 In 0.98 Sb 0.02 O 3 , LaIn 0.98 Sb 0.02 O 3 samples with additional impurity LaSbO 3 phase were prepared by solid-state reactions method. Their excitation and photoluminescence (PL) spectra were measured at room temperature. It was established that PL bands intensity of spectra obtained for samples of nominal composition La 0.95 Dy 0.05 In 0.98 Sb 0.02 O 3 , La 0.95 Ho 0.05 In 0.98 Sb 0.02 O 3 , La 0.90 Dy 0.05 Ho 0.05 In 0.98 Sb 0.02 O 3 is much higher than that of single-phase La 0.95…
Spectral properties of AIN ceramics
1997
Spectral properties of oxygen-related defects are studied in AIN ceramics at room temperatures. Original results concerning the photoluminescence under ultraviolet irradiation are obtained; they include the excitation spectrum and irradiation dose effects. The ultraviolet light energy storage and its release under irradiation with visible or infrared light in the form of the photostimulated luminescence has been observed in AIN ceramics. The properties of the photostimulated luminescence such as creation, emission and stimulation spectra are reported. For the explanation of the experimental results the mechanism of the recombination luminescence involving the oxygen-related defect is propos…
Valence-band splitting energies in wurtzite InP nanowires : Photoluminescence spectroscopy and ab initio calculations
2010
We investigated experimentally and theoretically the valence-band structure of wurtzite InP nanowires. The wurtzite phase, which usually is not stable for III-V phosphide compounds, has been observed in InP nanowires. We present results on the electronic properties of these nanowires using the photoluminescence excitation technique. Spectra from an ensemble of nanowires show three clear absorption edges separated by 44 meV and 143 meV, respectively. The band edges are attributed to excitonic absorptions involving three distinct valence-bands labeled: A, B, and C. Theoretical results based on “ab initio” calculation gives corresponding valence-band energy separations of 50 meV and 200 meV, r…
Isoelectronic series of oxygen deficient centers in silica: experimental estimation of homogeneous and inhomogeneous spectral widths
2008
We report nanosecond time-resolved photoluminescence measurements on the isoelectronic series of oxygen deficient centers in amorphous silica related to silicon, germanium and tin atoms, which are responsible of fluorescence activities at approximately 4 eV under excitation at approximately 5 eV. The dependence of the first moment of their emission band on time and that of the radiative decay lifetime on emission energy are analyzed within a theoretical model able to describe the effects introduced by disorder on the optical properties of the defects. We obtain separate estimates of the homogeneous and inhomogeneous contributions to the measured emission line width, and we derive homogeneou…
Photoluminescence spectral dispersion as a probe of structural inhomogeneity in silica
2011
We perform time-resolved photoluminescence measurements on point defects in amorphous silicon dioxide (silica). In particular, we report data on the decay kinetics of the emission signals of extrinsic oxygen deficient centres of the second type from singlet and directly excited triplet states, and we use them as a probe of structural inhomogeneity. Luminescence activity in sapphire (alpha-Al(2)O(3)) is studied as well and used as a model system to compare the optical properties of defects in silica with those of defects embedded in a crystalline matrix. Only for defects in silica did we observe a variation of the decay lifetimes with emission energy and a time dependence of the first moment…
Nature of the blue luminescence bands in PbWO4
1997
Abstract The photoluminescence spectrum of PbWO 4 is composed of blue and green bands, previously attributed to the regular WO 4 group and to the defect-related WO 3 group, respectively. Untill now only green emission was observed in the thermostimulated luminescence (TSL) above 77 K. Investigation of the TSL spectra starting from 20 K indicates that the blue band, being definitely present at least in the 28 K TSL peak, is also due to recombination emission at defect sites.
Inhomogeneous Broadening of Photoluminescence Spectra and Kinetics of Nanometer-Thick (Phenethylammonium)2PbI4 Perovskite Thin Films: Implications fo…
2021
An outstanding potentiality of layered two-dimensional (2D) organic–inorganic hybrid perovskites (2DHPs) is in the development of solar cells, photodetectors, and light-emitting diodes. In 2DHPs, an exciton is localized in an atomically thin lead(II) halide inorganic layer of sub-nanometer thickness as in a quantum well sandwiched between organic layers as energetic and dielectric barriers. In previous years, versatile optical characterization of 2DHPs has been carried out mainly for thin flakes of single crystals and ultrathin (of the order of 20 nm) polycrystalline films, whereas there is a lack of optical characterization of thick (hundreds of nanometers) polycrystalline films, fundament…
Homogeneous and inhomogeneous contributions to the luminescence linewidth of point defects in amorphous solids: Quantitative assessment based on time…
2008
The article describes an experimental method that allows to estimate the inhomogeneous and homogeneous linewidths of the photoluminescence band of a point defect in an amorphous solid. We performed low temperature time-resolved luminescence measurements on two defects chosen as model systems for our analysis: extrinsic Oxygen Deficient Centers (ODC(II)) in amorphous silica and F+ 3 centers in crystalline Lithium Fluoride. Measurements evidence that only defects embedded in the amorphous matrix feature a dependence of the radiative decay lifetime on the emission energy and a time dependence of the first moment of the emission band. A theoretical model is developed to link these properties to…
Fast Luminescence Studies of NaLaF4: Pr3+ Glass Ceramics
2021
Cathodoluminescence (CL) emission and photoluminescence (PL) emission and excitation spectra of $16\mathbf{Na}2\mathbf{O}-9\mathbf{NaF}-5\mathbf{LaF}_{3}-7\mathbf{Al}_{2}\mathbf{O}_{3}-63\mathbf{SiO}_{2}$ (mol%) activated with 3% $\mathbf{PrF}_{3}$ , hereinafter referred to as $\mathbf{NaLaF}_{4}:\mathbf{Pr}_{9}^{3+}$ have been investigated. In particular, CL spectra were measured with time resolution after excitation with a 120 keV electron beam. The characteristic Pr3+ ion emission with fast decay times $\tau_{1}=1.77$ ns and $\tau_{2}=52.97$ ns at peak intensity at 406 nm were observed, which correspond well to the emission bands of the $\mathbf{Pr}^{3+}$ ion in other luminescent materia…