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Effect of temperature on the structure and luminescence properties of Ag0.05Ga0.05Ge0.95S2-Er2S3 glasses
Abstract
In this article, we present the investigations of temperature dependent luminescence for the Ag0.05Ga0.05Ge0.95S2-Er2S3 glass system. The possibility to use temperature dependences of the photoluminescence of synthesized glasses for thermo sensors is considered. It is shown that logarithm of ratio of the integrated photoluminescence intensities for 980 and 600 nm (ln (I980/I660)) emission bands possess excellent linear dependence of temperature. At the same time, the nonlinear optical effects of two-photon absorption show substantial divergence from the sublinear dependences. These phenomena provide an opportunity to utilize Ag0.05Ga0.05Ge0.95S2-Er2S3 glasses for the fabrication of highly sensitive temperature sensor devices.
... Chalogenide and oxide glasses have long been intensely studied as promising materials for use in optoelectronic devices. They are used as passive and active media for laser technology, optical amplifiers in the visible and near-infrared ranges, and for the design of contactless sensors, fiber optic networks, and absorption photocatalysts [1][2][3][4][5][6][7]. For this purpose, sulfur-containing semiconductors are best compared to selenides and tellurides, as they are characterized by smaller interatomic distances and higher bandgap energy, so they can serve as a basic matrix for the introduction of admixtures to improve their electrical and optical properties [8][9][10]. ...
Erbium-doped chalcohalide glasses of A g C l ( I ) − G a 2 S 3 − L a 2 S 3 systems were synthesized by using the melting-cooling method. The introduction of a halide component leads to a decrease in the absorption coefficient, and the addition of erbium leads to the emergence of narrow absorption bands associated with transitions in the f-shell of E r 3 + ions. Five PL bands were detected in erbium-doped samples when excited by a laser with a 532 nm wavelength, the most intense of which at 980 nm and 1540 nm are promising for use in optical amplifiers and fiber optic networks. It was established that the glass-forming matrix A g C l − G a 2 S 3 − L a 2 S 3 , doped with E r 3 + ions, is an effective light-emitting medium in the near-infrared range. At the same time, the concentration quenching of the PL was observed in the A g I − G a 2 S 3 − L a 2 S 3 system when erbium content increases.
... Chalcogenide glassy system is particularly important because of its considerable applications in the field of infrared spectroscopy, lower phonon energy, high value of non-linear refractive indices and excellent glass-forming ability [1][2][3][4]. Chalcogenide glassy system exhibits higher electrical conductivity than their oxide counterparts as the high polarizability of sulfur or selenium plays vital role in the conduction process [5][6][7]. Recent works [7] exhibit that higher electrical conductivity of silver doped glassy systems should be favourable to enhance lifetime of battery material. It is also observed that Ag + doped chalcogenides may improve the ability of development of such glassy system [8]. ...
Ag2S doped Sulphur–Tellurium chalcogenide glassy system has been developed and their dielectric properties and electrical conductivity have been studied. Electrical conductivity via hopping of polarons in the present system is found to decrease due to large number of defects. TEM micrographs reveal the formation of Ag2S, Ag2Te and AgTe3 nanophases, whose sizes are found to decrease with compositions. Almond-West formalism has been used to analyze the thermally activated nature of conductivity spectra. Hunt’s model is used to reveal dielectric relaxation process with composition, which is justified by microstructure, revealed from TEM micrographs. Peak frequency (ωm) corresponding to imaginary modulus spectra shows Arrhenius relation. The results may reveal the opening for the development, significance and investigation of electrical and dielectric properties of chalcogenide glassy system.
... In recent days, LiI doped chalcogenide glassy system exhibits remarkable change in interfacial resistance and capacitance due to the formation of intergranular contact at the boundary [1]. Electrolyte materials are important for solid state battery applications in terms of their conduction mechanisms involving ionic transport and photoelectric conduction [2]. Recent studies [3] showed that silver based glassy compounds exhibit higher electrical conductivity, which should be helpful to increase the life-time of battery, made from such materials. ...
... Recent years saw increasing interest of scientists in the chalcogenide single crystals doped with rare earth metals (RE) [1]. This is due to the use of these materials in optoelectronic devices such as infrared light sources [2], up-converters [3], optical amplifiers [4], temperature [5,6] and radiation sensors [7]. Sulfide crystals and glasses have the largest transparency window in the visible and near infrared (IR) spectral range of all chalcogenide semiconductors [8]. ...
The investigation of the properties of novel multicomponent chalcogenide single crystals is one of the principal directions of modern semiconductor optoelectronics. Particular attention is paid to the study of the photoluminescence properties of rare earth-doped chalcogenide semiconductors in the visible and near infrared range. This is due to the use of these materials in telecommunication devices, laser and sensor technology. We describe here the growth technique of the single crystal (Ga 69.5 La 29.5 Er) 2 S 300 composition by solution-melt method. X-ray diffraction methods confirm its crystallization in the space group Pna2 1 . Optical absorption spectrum of the single crystal in the visible and near infrared range was studied. Using the functional dependence of (αhν) ² on hν for direct transitions, the bandgap energy of the semiconductor was determined as 1.99 ± 0.01 eV. The increase in the dopant concentration from 0.2 to 0.4 at. % Er does not significantly change the band structure of the single crystal, therefore the bandgap energy is unchanged as well. Narrow absorption bands were recorded that are related to the transitions ⁴ I 15/2 → ⁴ I 11/2 , ⁴ I 15/2 → ⁴ I 9/2 , ⁴ I 15/2 → ⁴ F 9/2 in the f-shell of erbium ions. High concentration of energy levels in the band gap associated with the structure defects of the crystal results in the high value of the optical absorption coefficient. Photoluminescence excitation was achieved by a 532 nm (2.33 eV) laser at 150 mW. Intense Stokes photoluminescence bands were recorded at 1.53 and 0.805 eV, as well as lower-intensity maxima at 1.45, 1.27, 1.88 eV. These emission bands correspond to the transitions ⁴ I 9/2 → ⁴ I 15/2 , ⁴ I 13/2 → ⁴ I 15/2 , ⁴ S 3/2 → ⁴ I 13/2 , ⁴ I 11/2 → ⁴ I 15/2 , ⁴ F 9/2 → ⁴ I 15/2 in Er ³⁺ ions, respectively. An energy transition diagram for the f-shell of Er ³⁺ ions in the (Ga 69.5 La 29.5 Er) 2 S 300 single crystal was plotted. The emission mechanism and the important role of the cross-relaxation processes between the ground and excited states of Er ³⁺ ions were established. As a result of the influence of the local crystalline field on erbium ions, the Stark splitting of the ⁴ I 13/2 , ⁴ I 15/2 levels and the widening of the photoluminescence band with the maximum at 0.805 eV is observed. Intense infrared bands of the photoluminescence (1.53 and 0.805 eV) create prerequisites for using the (Ga 69.5 La 29.5 Er) 2 S 300 single crystal in sensor technology and optoelectronic devices.
... Сульфідні напівпровідники, порівняно з іншими, характеризуються найбільшою прозорістю у видимому та близькому інфрачервоному діапазоні. Це створює переваги при використанні їх в якості перетворювачів світла [5] активних і пасивних елементів в лазерній [6,7] та сенсорній техніці [8][9][10]. Сульфіди германію та галію найбільше поширені серед халькогенідних стекол внаслідок великої області склоутворення та можливості в широких межах змінювати вміст компонентів для отримання оптимального складу [11,12]. ...
Glasses of the composition (70–X) mol.% Ga2S3 - 30 mol.% La2S3 - X Er2S3 (at X = 0, 1, 3) were synthesized and the optical absorption spectra at room temperature were studied. Photoluminescence spectra in the 2.53 - 0.73eV range at 300 and 80K were investigated. Intense PL maxima at 2.25, 1.88, 1.45, 1.26, 1.13, 0.81 eV were found which correspond to transitions in the f-shell of erbium ions. The redistribution of the intensity of PL peaks with temperature was analyzed based on the energy transition diagram of erbium ions.
Стекла 20 моль% Ga2S3 – 60 моль% GeS2 – 20 моль% Sb2S3: Er2S3 (1–4 моль%); Nd2S3 (2 моль%) отримано методом гартування. На основi дослiджень спектрiв оптичного поглинання встановлено смуги поглинання iз максимумами 655, 755, 810, 885, 980 i 1540 нм. При збудженнi фотолюмiнесценцiї випромiнюванням з λ = 805 нм у спектрi з’являються смуги з максимумами при 1070, 1350, 1540, 1700 i 2490 нм, що вiдповiдає переходам 4F3/2 → 4I11/2 (Nd3+), 4F3/2 → 4I13/2 (Nd3+), 4I13/2 → 4I15/2 (Er3+), 4I9/2 → 4I13/2 (Er3+), 4I13/2 → 4I9/2 (Nd3+) у f-оболонках обох рiдкоземельних металiв. Високi значення коефiцiєнта пропускання скляної матрицi та iнтенсивна фотолюмiнесценцiя, зумовлена Er3+ та Nd3+, роблять її придатною для розробки оптоелектронних пристроїв, якi працюють в ближньому та середньому IЧ-дiапазонах.
Series glasses with compositions (100–х-y) Ga2S3 – х La2S3 – y Er2S3 (х = 30, 35, 40; y = 0, 1, 3 mol.%) were synthesized and their optical properties were examined. Glass-forming region for the novel La2S3–Ga2S3 system was determined. Composition−dependent optical absorption spectra within the spectral range 480–1020 nm and photoluminescence (PL) under excitation by laser radiation with 532 nm wavelength were measured. The PL maxima were found at 660, 810, 860, 980 and 1540 nm. The origin of the excited states in Er³⁺ ions was analyzed using an energy diagram. PL decay kinetics processes were analyzed in detail, within the frame of the two exponents model. This one indicates that the Erbium ions emitting in both red and IR spectral ranges are embedded in the glass matrices a like as separate ions or form clusters of erbium ions. The presented research results along with literature data indicate a wide opportunity for potential applications like thermal and radiation sensors, non-linear optical triggers, up-converters, contactless thermometers or active media for IR lasers.
A series of CaSrSiO4: Yb³⁺, Er³⁺, xAg phosphors have been prepared by high-temperature solid-state reaction method. Scanning electron microscope (SEM) images show that more small spherical particles gather together to form bigger cluster when Ag nanoparticles are co-doped into CaSrSiO4: 9Yb³⁺, 1Er³⁺ nanophosphor. Photoluminescence intensities of samples co-doped Ag nanoparticles enhance significantly and the optimized Ag concentration is 0.6 mol%. The fluorescence intensity ratio, the absolute sensitivity, relative sensitivity and temperature resolution are measured, computed and discussed in the range of 303–703 K. The results show that all sensing performances of CaSrSiO4: Yb³⁺, Er³⁺, 0.6Ag phosphor are superior to these of the sample un-doped Ag particles and the maximum SA value can go up to 7.3 × 10–3 K⁻¹, indicating that CaSrSiO4: 9Yb³⁺, 1Er³⁺, 0.6Ag designed and prepared in this work is a promising optical high-temperature sensing material and it is appropriate to practical application in comprehensive fields.
The quasi-ternary systems Er2S3–In2S3–Ga2S3 was investigated by X-ray method, the isothermal section of the system at 770 K was constructed. Using X-ray structure analysis the crystal structures of the new compounds Ga2.78In3.88Y3.35S15 (I), Ga2.98In2.66Er4.37S15 (II), Ga3.37In1.26Tm5.37S15 (III), Ga3.46In1.58Yb4.96S15 (IV) were calculated. They crystallize in the space group C2/m with lattice parameters: a = 23.4104(6) Å, b = 3.81242(12) Å, c = 12.5460(4) Å, β = 90.775(3)° (I); a = 23.5181(17) Å, b = 3.8064(3) Å, c = 12.5592(9) Å, β = 90.954° (II); a = 23.5474(8) Å, b = 3.78634(15) Å, c = 12.5164(4) Å, β = 90.988(3)° (III), a = 23.4427(7) Å, b = 3.77641(8) Å, c = 12.4970(3) Å, β = 90.970° (IV). The photoluminescent spectra of the (Ga54.59In44.66Er0.75)2S300 single crystal were investigated. With the decreasing of the temperature till 300, 250, 200, 150 K the intensity of the photoluminescent spectra decreases. The position and shape of the spectra do not change according to the temperature decreasing. The maximum of the photoluminescent spectra (0.81 eV) corresponds to the transitions ⁴І13/2 → ⁴I15/2 in the f-shell of Er³⁺ ions.
AgI‐based Ge–Sb–S, Ga–Sb–S, and Ge–Ga–Sb–S chalcogenide glasses were designed and prepared by melt‐quenching, thereafter their thermal properties and conductive performance were comparatively investigated on the basis of their composition‐induced network structures. Glass transition in each sample was examined by DSC measurements. Results showed that the samples containing Ge had a higher thermal stability than the Ga–Sb–S–AgI sample, and the Ge–Sb–S–AgI sample obtained had the highest conductivity ion. Raman spectrum analysis was performed, and the results indicated that the [GeS4‐xIx] structural units and [SbS3−xIx] pyramids in the matrix produced effective ion transport channel for dissolved conductive Ag⁺ ions. In the matrix containing Ga, the [Ga(Ge)S4‐xIx] structure was consumed by part of [S3Ga–GaS3] ethane‐like units, which had no contribution to the ion transition framework. The study provided the directions for composition and structure configuration control in effective conductive chalcogenide glasses.
Ge-In-Se system, similar to many other chalcogenide glasses, has attracted much attention due to its interesting physical properties and applications. This article reports thermal analysis and estimation of activation energies of the glass transition and amorphous-crystallization transformation of Ge13In8Se79 chalcogenide glass. The kinetic parameters were investigated under a non-isothermal condition at different heating rates (7–40 K/min) using differential scanning calorimetric (DSC) technique. The amorphous nature of the samples was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The activation energy was calculated from DSC data using five isoconversional methods: Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), Tang, Starink, and Vyazovkin. The results confirm that the activation energy of crystallization varies and depends on the degree of crystallization as well as temperature. It was also observed that the transformation from amorphous to the crystalline structure is complex involving different mechanisms of nucleation, diffusion, and growth.
Preparation technology, the structure determination, multiband luminescence and nonlinear optical properties (NLO) of the chalcogenide glasses are subject of present work. The Ag0.05Ga0.05Ge0.95S2Er2S3 glass samples with two different 0.12 and 0.27 at.% Er content were prepared by classical two-stage melt-quenching method. Glass state and morphology were confirmed by X-ray and EDS techniques. Influence of the Erbium doping on the luminescence and NLO properties was investigated. Based on the diagram of energy levels for the Er3+ ions, we proposed a model that explains photoluminescence (PL) emission mechanism. It should be emphasized that investigated glasses (in comparison with other materials) are exceptional in that all bands of PL are intense due to small energy losses at excitation and emission of ions Er3+. The photoinduced second and third harmonic generations have been measured in the reflected geometry and compared with reference – BiB3O6 (BBO): 10%Nd crystal.
The monograph describes the technique of the synthesis of glasses and the
method of the growth of erbium-doped single crystals. The photoluminescence
spectra of Ag0.05Ga0.05Ge0.95S2-Er2S3 glasses and glasses from the Ga2S3-La2S3-Er2S3
system have been investigated in the visible and near-infrared ranges. According to
the energy transitions in the erbium ions, a radiation mechanism for conversion and
up-conversion luminescence has been established. The role of structural ordering
and the influence of defects on the radiation efficiency of Er3+ ions have been
investigated. The spectra of photoluminescence of (Ga54.59In44.66Er0.75)2S300 and
(Ga69.75La29.75Er0.5)2S300 single crystals have been studied. The efficiency of the
radiation of the amorphous and crystalline materials has been compared. Also, the
temperature dependence of the integral intensity of the radiation of glasses and
single crystals has been studied. It is established that in a limited temperature range,
these materials can be used for the manufacture of non-contact optical
thermosensors.
Electronic structure and optical properties were studied for novel (Ga70La30)2S300 and (Ga69.75La29.75Er0.5)2S300 single crystals synthesized by solution-melt technique. In particular, X-ray photoelectron spectroscopy (XPS) was used to measure core-level binding energies and valence-band spectra for as-synthesized and Ar⁺ ion-irradiated surfaces of these crystals. Presented XPS measurements show that the (Ga70La30)2S300 and (Ga69.75La29.75Er0.5)2S300 single crystals are rather stable in relation to Ar⁺ ion-irradiation. X-ray emission (XE) S Kβ1,3 and Ga Kβ2 bands were measured for the (Ga70La30)2S300 crystal giving information on the energy distribution of the S 3p and Ga 4p states, respectively. A comparison of these XE bands on a common energy scale with the XPS valence-band spectrum of (Ga70La30)2S300 indicates that the principal contribution of the S 3p and Ga 4p states occurs mainly at the top and in the central part of the valence band, respectively. In addition, optical absorption and photoluminescence spectra of the crystals were explored. Energy band gap values are estimated as 2.01 and 1.99 eV at room temperature for the (Ga70La30)2S300 and (Ga69.75La29.75Er0.5)2S300 crystals, respectively. Observed high-intensity green photoluminescence band when excited by a laser emitting at 810 nm suggests that the (Ga69.75La29.75Er0.5)2S300 crystal is a very attractive material for infrared to visible light conversion.
Using solution-melt method two single crystals, (Ga70La30)2S300, (Ga69.75La29.75Er0.5)2 S300, were grown. The maxima of the luminescent radiation in the photoluminescence spectrum of the (Ga70La30)2S300, (Ga69.75La29.75Er0.5)2 S300 single crystal correspond to the intracentric transitions in the erbium ions: ²H11/2 → ⁴I15/2 (525 nm) and ⁴S3/2 → ⁴I15/2 (545 nm).
BeO Dosimeters; Its synthesis and Luminescence Characteristics
It was shown a possibility to use the (Ga54.59In44.66Er0.75)2S300 single crystal as optoelectronics detectors of gamma-irradiation using photoinduced nonlinear optical methods and photoluminescence. The crystal was irradiated by a ⁶⁰Co source at ambient conditions. The average energy of the incident γ-rays was about 1.25 MeV. The luminescence excitation was carried out using a 150 mW cw laser with wavelength 532 nm. The best results sensitive to the gamma irradiation were obtained for the third harmonic generations (THG) of the materials treated by bicolor Er: glass laser two beams propagated at angles about 21°–24°. The photoinduced gratings profile also were explored and their correlation with the gamma radiation and nonlinear optical response were explored. Comparison of photoluminescence and photoinduced nonlinear optical sensitivity to radiations was performed.
This work reports the high-pressure and high-temperature (HP-HT) synthesis of pure monoclinic phase of GdNbO4:Bi3+ phosphors. X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence, and IR spectra were utilized to characterize the synthesized phosphors. The crystal structure distortions operated by the pressure leads to tunable emission varying from blue to yellow. A small increase of the probability of non-radiative energy transfer with increase of pressure is observed. It is shown that the efficiency of the energy transfer process is dependent on pressure. The calculations of CIE chromaticity coordinates were performed.
NbN thin films are the good candidate for superconducting integrated devices. The sputter deposition of NbN on Si or SiO is desirable due to its low cost and availability of high volume equipment. In this study, The NbN thin films films have been deposited over Si and buffer layers including oxidized Si by reactive magnetron sputtering. Sputtering of a Nb target in different compositions of Ar/N2 gas was also used for the preparation of NbN superconducting thin films. Influence of various sputtering power, substrate temperatures and Ar/N2 gas ratio was also investigated on the superconducting transition temperature (Tc). The results showed that increase in the sputtering power and substrate temperature caused increased on the TC. Thus optimum values are observed via R-T curves and calculation of Residual-resistance ratio RRR values. It is shown that the deposition temperature and the flux of N2 have a strong effect on the preferred orientation, while the critical temperature of the films is influenced by the quality of the original vacuum. Finally, we found that the conditions for TC depend primarily on the N and Ar sputter deposition pressures on sputter deposited NbN films.
Single crystals (Ga55In45)2S300 and (Ga54.59In44.66Er0.75)2S300 possessing space group P61 were successfully grown and explored with respect to laser induced piezooptics. Their structural properties were studied by Raman spectroscopy and additionally, dependence of different gamma ray doses on the photoinduced piezo-optical responses were also explored. Structural parameters were evaluated using the Rietveld methods following the X-ray diffraction data. The chemical composition of the synthesized samples was determined by EDS analysis. We discussed the influence of Er³⁺-doping on the crystal structure and piezo-optical properties. It was established that these crystals behavior is very sensitive to γ−irradiation dose and therefore they are promising for applications as elastooptical radiation sensors.
A strategy has been adopted for simultaneous morphology manipulation and upconversion luminescence enhancement of β-NaYF4:Yb(3+)/Er(3+) microcrystals by simply tuning the KF dosage. X-ray power diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectra (PL) were used to characterize the samples. The influence of molar ratio of KF to Y(3+) on the crystal phase and morphology has been systematically investigated and discussed. It is found that the molar ratio of KF to Y(3+) can strongly control the morphology of the as-synthesized β-NaYF4 samples because of the different capping effect of F(-) ions on the different crystal faces. The possible formation mechanism has been proposed on the basis of a series of time-dependent experiments. More importantly, the upconversion luminescence of β-NaYF4:Yb(3+)/Er(3+) was greatly enhanced by increasing the molar ratio of KF to RE(3+) (RE = Y, Yb, Er), which is attributed to the distortion of local crystal field symmetry around lanthanide ions through K(+) ions doping. This synthetic methodology is expected to provide a new strategy for simultaneous morphology control and remarkable upconversion luminescence enhancement of yttrium fluorides, which may be applicable for other rare earth fluorides.
A strategy to realize dual-mode luminescence from identical Tb3+ is provided via Gd-sublattice-mediated energy migration and core-shell engineering techniques. By optimizing structure of NaGdF4:Yb/Tm@NaGdF4:Ce/Tb nanoarchitecture, both upconversion and downconversion emissions, originating from 5D4 → 7F6,5,4,3 transitions of Tb3+, are achieved through Yb3+ → Tm3+ → [Gd3+]n → Tb3+ and Ce3+ → [Gd3+]n → Tb3+ energy transfer processes, respectively.
In this work study of photoluminescence (PL) spectra in the Er-doped glasses of the AgGaS2-GeS2 system is presented. Emission spectra of the glasses at T ≈ 292 K, excited by light with λex ≈ 980 nm and λex ≈ 532 nm are described well by transitions in the 4f-shell of Er3+ ions. Spectral curves of the emission can be deconvoluted into four Gaussian components. Er atoms are localized both in the glass matrix and (with increased concentration) around large structural damages (heterogeneities) which are drains for them. This causes broadening of the emission bands of Er3+ ions that are localized around heterogeneities. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
The concentration dependences of the optical properties of glassy alloys in the HgS-Ga2S3-GeS2 system have been investigated in the spectral range 2.0–2.9 eV. The energy gap E
g
of glasses has been estimated, and the dependence of the energy gap on the content of HgS and Ga2S3 has been analyzed. The spectral dependences α(hν) for glasses in the system under investigation in the fundamental absorption range are described by the Urbach rule. The
alloys containing ≥ 20 mol % (HgS + Ga2S3) are characterized by an ordering and a decrease in the energy gap E
g
, which are explained by the changes in the short-range order in the arrangement of the atoms involved in the composition
of alloys. It has been assumed that, at high concentrations of modifiers, there can arise microscopic inclusions, i.e., different
defects, which can scatter light and decrease the transparency of glassy alloys.
We report the properties of thermally evaporated Ge11.5As24Se64.5 chalcogenide films ion implanted at energies of 2.25MeV with Erbium at concentrations up to 0.4 mol%. The effect of post implant annealing on the refractive index of the films and on the ⁴I13/2→⁴I15/2 Er transition was studied. Photoluminescence was found to increase significantly and a lifetime of 1.35 ms was obtained in films annealed at 180°C. Different apparent lifetimes for the ⁴I13/2→⁴I15/2 transition were obtained for 980nm and 1470nm pumps and the origins of this phenomenon are discussed.
Quantum size effect in the photoluminescence properties of p-type semiconducting transparent CuAlO2 nanoparticles J. Appl. Phys. 112, 114329 (2012) Effects of hydrogen on the electronic properties of Ga(AsBi) alloys Appl. Phys. Lett. 101, 222103 (2012) Visible photoluminescence from MgAl2O4 spinel with cation disorder and oxygen vacancy J. Appl. Phys. 112, 103523 (2012) Effect of calcinations on electrical properties of TiO2 nanotubes J. Appl. Phys. 112, 104308 (2012) One step synthesis of pure cubic and monoclinic HfO2 nanoparticles: Correlating the structure to the electronic properties of the two polymorphs
We reported a new strategy to remarkably improve upconversion luminescence of Ln3+-doped nanoparticles via an active-core/luminescent-shell/active-shell engineering technique. By optimizing the structure of a NaGdF4:Yb@NaYF4:Yb/Er@NaGdF4:Yb sandwich-like nanoarchitecture, significant enhancement of upconversion emission intensity was realized with the help of the synergistic actions of the suppression of Er-defect energy transfer and the efficient energy transfer from Yb3+ in both active-core and active-shell to Er3+ in luminescent-shell.
In this paper, a series of color-tunable phosphors from green to yellow and eventually to red have been successfully synthesized with efficient Ce3+ → Tb3+ → Eu3+ energy transfer in hexagonal NaYF4 host. The energy transfer processes from Ce3+ to Tb3+ and from Tb3+ to Eu3+ and the corresponding energy transfer efficiencies are carefully investigated by the photoluminescence excitation spectra, emission spectra and the decay curves. Impressively, the Ce3+ → Tb3+ → Eu3+ energy transfer mechanism has been proposed and can be attributed to the strong absorption of ultraviolet light by sensitizers (Ce3+), followed by energy migration to Tb3+ ions, from which the energy is finally transferred to activators (Eu3+). Furthermore, the temperature sensing behavior of β-NaYF4:Ce3+/Tb3+/Eu3+ under 248 nm ultraviolet light excitation is also studied to explore the possible application of the as-synthesized sample in optical thermometry. Evidently, the results suggest that the investigated β-NaYF4:Ce3+/Tb3+/Eu3+ sample may be a promising candidate for optical temperature sensor.
The photoluminescence (PL) spectra of Ag0:05Ga0:05Ge0:95S2-Er2S3 glasses excited by a laser diode operating at 980 nm have been investigated. The broadening of the PL band of the glasses with increase in the Er content has been found, by calculating a full-width at half-maximum (FWHM) and the effective width Δλef. Inhomogeneities with dimensions of 6-7 μm have been disclosed in the glassy alloys; their concentration increases with the erbium content and influence the width of the PL spectra.
This chapter discusses the optical properties of chalcogenide glasses and fibers for infrared applications. The chapter describes the theory of optical transmission including intrinsic material losses and extrinsic losses due to impurity absorptions. Refractive index and material dispersion of bulk glass are reviewed. Optical fiber transmission loss and laser power delivery data are discussed. Nonlinear optical processes are explored for active devices including Raman amplification, supercontinuum generation, stimulated Brillouin scattering for slow-light applications and four wave mixing.
Paramagnetic defects in erbium-doped γ-irradiated chalcogenide glasses were investigated by EPR method. Vacancy nature of defects and the dependence of their concentration on the irradiation dose and erbium content were determined. The measurement of the static magnetization revealed the presence of paramagnetic and ferromagnetic subsystems caused by isolated Er3+ ions and ion clusters, respectively. PL spectra of 4f-4f transitions of Er3+ ions and the radiation mechanism of γ-irradiated glasses were investigated. It was determined that PL intensity depends on the number of radiation induced defects and on the nature of the distribution of erbium which were determined by EPR and magnetic susceptibility.
This chapter is mainly devoted to the second-order nonlinear optical processes induced in optically isotropic chalcogenide glasses. The chapter is divided into two main parts related to the second-order nonlinear optical effects in near infrared and IR stimulated processes obtained in chalcogenide glasses. The different processes applied to break the centrosymmetry of glasses, which enables their use for the conversion of wavelength and for electro-optical purposes, are described: optical poling, poling assisted by e-beam or thermal poling. The origin and mechanisms of the phenomena induced by these processes, dedicated to the generation in glasses of a second-order nonlinear optical response, are discussed. In addition to these extrinsic methods, the interest in glass-ceramics containing non-centrosymmetric crystalline phases is considered. This chapter is also dedicated to some experiments describing IR-laser-stimulated changes of main linear and nonlinear optical constants in chalcogenide glasses. The origin of the observed phenomena is described within phenomenological and microscopic approaches, with special attention being paid to the contribution of phonons.
The quasiternary system Ag2S-Ga2S3-In2S3 was investigated by differential thermal, X-ray diffraction analyses. The phase diagram of the Ga2S3-In2S3 system and nine polythermal sections, isothermal section at 820 K and the liquidus surface projection were constructed. The existence of the large solid solutions ranges of binary and ternary compounds was established. The range of the existence of the quaternary phase AgGaxIn5-xS8 (2.25≤x≤2.85) at 820 K was determined. The single crystals (Ga55In45)2S300 and (Ga54.59In44.66Er0.75)2S300 were grown by a directional crystallization method from solution-melt. Optical absorption spectra in the 500-1600 nm range were recorded. The luminescence of the (Ga54.59In44.66Er0.75)2S300 single crystal shows a maximum at 1530 nm for the excitation wavelengths of 532 and 980 nm at 80 and 300 K.
The emission and life time decay characteristics of Eu3 + ions in barium boro-phosphate glasses mixed with different concentrations of Al2O3 are studied. The emission spectra exhibited bands due to 5D0 → 7F0, 7F1, 7F2, 7F3, 7F4 transitions of Eu3 + ions. The highest intensity of these transitions is observed when the glasses are mixed with 3.0 mol% of Al2O3. Using the emission spectra, the Judd–Ofelt (J–O) parameters and the radiative parameters viz., emission probability, A, the radiative lifetime, τ, and the fluorescent branching ratio, β of different transitions originated from 5D0 level of Eu3 + ions are evaluated. The results have been analyzed as a function of Al2O3 concentration with the aid of IR spectral data. The IR spectral data have indicated that Al3 + ions participate in larger proportions in octahedral positions in the glasses mixed with 3.0 mol% of Al2O3, which induce bonding defects, de-cluster the Eu3 + ions and facilitate for minimizing the emission losses due to quenching. The quantitative analysis of these results further indicated that 3.0 mol% of Al2O3 is optimal for achieving the highest luminescence efficiency in these glasses.
The emission and life time decay characteristics of Eu3 + ions in barium boro-phosphate glasses mixed with different concentrations of Al2O3 are studied. The emission spectra exhibited bands due to 5D0 → 7F0, 7F1, 7F2, 7F3, 7F4 transitions of Eu3 + ions. The highest intensity of these transitions is observed when the glasses are mixed with 3.0 mol% of Al2O3. Using the emission spectra, the Judd–Ofelt (J–O) parameters and the radiative parameters viz., emission probability, A, the radiative lifetime, τ, and the fluorescent branching ratio, β of different transitions originated from 5D0 level of Eu3 + ions are evaluated. The results have been analyzed as a function of Al2O3 concentration with the aid of IR spectral data. The IR spectral data have indicated that Al3 + ions participate in larger proportions in octahedral positions in the glasses mixed with 3.0 mol% of Al2O3, which induce bonding defects, de-cluster the Eu3 + ions and facilitate for minimizing the emission losses due to quenching. The quantitative analysis of these results further indicated that 3.0 mol% of Al2O3 is optimal for achieving the highest luminescence efficiency in these glasses.
Theoretical and experimental studies of the AgxGaxGe1-xSe2 (x = 0.333, 0.250, 0.200, 0.167) single crystals are performed. These crystals possess a lot of intrinsic defects which are responsible for their optoelectronic features. The theoretical investigations were performed by means of DFT calculations using different exchange -correlation potentials. The experimental studies were carried out using the modulated VUV ellipsometry for dielectric constants and birefringence studies. The comparison of the structure obtained from X-ray with the theoretically optimized structure is presented. The crucial role of the intrinsic defect states is manifested in the choice of the exchange correlation potential used. The data may be applicable for a large number of the ternary chalcogenides which are sensitive to the presence of the local disordered states near the band edges.
The absorption spectra and up-conversion luminescence of glassy alloys (100−X)Ag0.05Ga0.05Ge0.95S2–(X)Er2S3, where Х=0.42, 0.25, and 0.18 mol% (0.27; 0.16; and 0.12 at% Er, respectively) at excitation using diode laser with wavelength 980 nm in the range 450–1050 nm were investigated. We propose mechanism of emission in the glasses based on the model of intra-4f shell transitions in Er3+ ion. The influence of the formation of the structural units on the optical properties of the glasses using Raman spectroscopy that is important when designing the erbium-containing environments in laser technology was studied.
The theoretical study of two-photon absorption (TPA) properties of a non-conjugated dimer is related to cooperative effects between monomers. This effect leads to a strong increase of the TPA cross-section. This phenomenon is studied in the case of the three-level model.
The atomic structure of Er2S3 was refined by single-crystal X-ray diffraction methods. The compound is isostructural to the δ-Ho2S3 structure type, which has monoclinic symmetry and space group P21/m, a=10.072 (1) Å, b=3.976 (2) Å, c=17.389 (2) Å, β=98.66(1)°, Z=6. Refinement proceeded to R=0.037 for 1745 observed reflections. Experimental high-resolution micrographs (structural images) were obtained along the [010] zone axis and compared with simulated micrographs (using the multislice Cowley–Moodie method) obtained from the average X-ray structure model. Due to electron beam damage, nanocrystallites of ErS (with NaCl-type structure) were formed on the crystal edges. Some disorder was observed by electron diffraction, probably caused by antiphase boundaries.
A review of some properties of chalcogenide glasses and the current status of their applications is given. Techniques to characterize the linear and non-linear properties of these glasses are introduced and used to measure the optical constants of chalcogenide glasses in the form of bulk, thin film and fiber. Different techniques for the fabrication of gratings and waveguides in these glasses are described. Achievable efficiencies of gratings, as well as propagation losses of fabricated waveguides, are presented. The possibilities of fabricating active devices, such as fiber amplifiers and lasers, are presented. Finally, a novel application of chalcogenide glasses, namely all-optical switching for the fabrication of efficient femtosecond switches, is introduced.
Temperature dependence of the two-photon absorption (TPA) excited by Er 3 þ : glass laser wavelength 1.54 μm for the Ag 28 Ga 28 Ge 532 -Er 2 S 3 glass samples at different Er 3 þ ions content
- Fig
Fig. 12. Temperature dependence of the two-photon absorption (TPA) excited by
Er 3 þ : glass laser wavelength 1.54 μm for the Ag 28 Ga 28 Ge 532 -Er 2 S 3 glass samples at
different Er 3 þ ions content.
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