TeO2-ZnO-Na2O-K2O玻璃中Er^3＋离子掺杂浓度对其发光及荧光寿命的影响

测量了不同掺杂浓度下Er^3+离子在碲酸盐玻璃中的吸收光谱、发射光谱和Er^3+离子的荧光寿命，计算了Er^3+离子的发射截面σc，分析了Er^3+离子掺杂浓度对其发光强度和荧光寿命的影响．结果表明，Er^3+离子掺杂浓度较低时，对其荧光强度和荧光寿命没有显著的影响；掺杂浓度高时，出现了浓度猝灭效应，使Er^3+离子荧光光强度降低，荧光寿命下降．实验确定了掺杂浓度最优值，同时对浓度猝灭机制进行了分析．

Gd3+ -> Eu2+ energy transfer in BaLiF3 : Eu, Gd

Photoluminescence characteristics and the energy transfer between Gd3+ and Eu2+ in BaLiF3,, matrix have been investigated. A series of concentrations of Gd3+ ion with a fixed Eu2+ concentration doped in BaLiF3 : Gd3+, Eu2+ has been studied. When the doping concentration for Gd3+ was 0.3%,, the system reached the highest energy transfer efficiency. Due to the competitive absorption for the Gd3+ and the Eu2+ ions in BaLiF3 : Gd3+ : Eu2+, when the doping concentration for Gd3+ ion exceeded 0.3 Vo, the continuously increasing concentration of Gd3+ ions caused the competitive absorption ratio for Gd3+ increasing and the emission intensity of Eu2+ decreasing. The energy transfer processes were discussed, while the transfer probability was calculated to be 1.35 X 10(5) s(-1).

Effect of doping concentration on the structural and optical properties of pure and tin doped zinc oxide thin films by nebulizer spray pyrolysis (NSP) technique

Pure and tin doped zinc oxide (Sn:ZnO) thin films were prepared for the first time by NSP technique using aqueous solutions of zinc acetate dehydrate, tin (IV) chloride fendahydrate and methanol. X-ray diffraction patterns confirm that the films are polycrystalline in nature exhibiting hexagonal wurtzite type, with (0 0 2) as preferred orientation. The structural parameters such as lattice constant ('a' and `c'), crystallite size, dislocation density, micro strain, stress and texture coefficient were calculated from X-ray diffraction studies. Surface morphology was found to be modified with increasing Sn doping concentration. The ZnO films have high transmittance 85% in the visible region, and the transmittance is found to be decreased with the increase of Sn doping concentration. The corresponding optical band gap decreases from 3.25 to 3.08 eV. Room temperature photoluminescence reveals the sharp emission of strong UV peak at 400 nm (3.10 eV) and a strong sharp green luminescence at 528 nm (2.34 eV) in the Sn doped ZnO films. The electrical resistivity is found to be 10(6) Omega-cm at higher temperature and 10(5) Omega-cm at lower temperature. (C) 2012 Elsevier Ltd. All rights reserved.

Room temperature synthesis of Mn2+ doped ZnS d-dots and observation of tunable dual emission: Effects of doping concentration, temperature, and ultraviolet light illumination

Mn2+ doped (0-50.0 molar %) ZnS d-dots have been synthesized in water medium by using an environment friendly low cost chemical technique. Tunable dual emission in UV and yellow-orange regions is achieved by tailoring the Mn2+ doping concentration in the host ZnS nanocrystal. The optimum doping concentration for achieving efficient photoluminescence (PL) emission is determined to be similar to 1.10 (at. %) corresponding to 40.0 (molar %) of Mn2+ doping concentration used during synthesis. The mechanism of charge transfer from the host to the dopant leading to the intensity modulated tunable (594-610 nm) yellow-orange PL emission is straightforwardly understood as no capping agent is used. The temperature dependent PL emission measurements are carried out, viz., in 1.10 at. % Mn2+ doped sample and the experimental results are explained by using a theoretical PL emission model. It is found that the ratio of non-radiative to radiative recombination rates is temperature dependent and this phenomenon has not been reported, so far, in Mn2+ doped ZnS system. The colour tuning of the emitted light from the samples are evident from the calculated chromaticity coordinates. UV light irradiation for 150 min in 40.0 (molar %) Mn2+ doped sample shows an enhancement of 33% in PL emission intensity. (C) 2013 American Institute of Physics. http://dx.doi.org/10.1063/1.4795779]

Concentration quenching in erbium-doped tellurite glasses

Er2O3-doped TeO2-ZnO-La2O3 modified tellurite glasses were prepared by the conventional melt-quenching method, and the Er3+ : I-4(13/2) -> I-4(15/2) fluorescence properties have been studied for different Er3+ concentrations. Infrared spectra were measured in order to estimate the exact content of OH- groups in samples. Based on the electric dipole-dipole interaction theory, the interaction parameter, C-Er,(Er), for the migration rate of Er3+ : I-4(13/2) -> I-4(13/2) in modified tellurite glass was calculated. Finally, the concentration quenching mechanism using a model based on energy transfer and quenching by hydroxyl (OH-) groups was presented. (c) 2005 Elsevier B.V. All rights reserved.

Effects of Yb concentration on the fluorescence spectra of Yb-doped YAlO3 single crystals

0.5 at.% Yb:YAlO3(YAP), 5 at.% Yb:YAP and 15 at.% Yb:YAP were grown using the Czochralski method. Their absorption and fluorescence spectra were measured at room temperature and their emission line shape was calculated using the method of reciprocity. It was observed that the fluorescence spectra changed appreciably with the increasing of Yb concentration. For 0.5 at.% Yb:YAP, the line shape of fluorescence is very similar with the calculated emission line shape; with the increasing of Yb doping concentration, the line shape of fluorescence is very different from the calculated emission line shape. These phenomena are caused by the strong self-absorption at 979 and 999 nm for Yb:YAP. (c) 2005 Elsevier B.V. All rights reserved.

High quantum efficiency and high concentration erbium-doped silica glasses fabricated by sintering nanoporous glasses

A new method was used to prepare erbium-doped high silica (SiO2% > 96%) glasses by sintering nanoporous glasses. The concentration of erbium ions in high silica glasses can be considerably more than that in silica glasses prepared by using conventional methods. The fluorescence of 1532 nm has an FWHM (Full Wave at Half Maximum) of 50 nm, wider than 35 nm of EDSFA (erbium-doped silica fiber amplifer), and hence the glass possesses potential application in broadband fiber amplifiers. The Judd-Ofelt theoretical analysis reflects that the quantum efficiency of this erbium-doped glass is about 0.78, although the erbium concentration in this glass (6 x 103) is about twenty times higher than that in silica glass. These excellent characteristics of Er-doped high silica glass will be conducive to its usage in optical amplifiers and microchip lasers.

Annealing study of carrier concentration in gradient-doped GaAs/GaAlAs epilayers grown by molecular beam epitaxy

We measured the carrier concentration distribution of gradient-doped GaAs/GqAlAs epilayers grown by molecular beam epitaxy before and after annealing at 600 degrees C, using electrochemical capacitance voltage profiling, to investigate the internal variation of transmission-mode GaAs photocathodes arising from the annealing process. The results show that the carrier concentration increased after annealing. As a result, the total band-bending energy in the gradient-doped GaAs emission layer increased by 25.24% after annealing, which improves the pbotoexcited electron movement toward the surface. On the other hand, the annealing process resulted in a worse carrier concentration discrepancy between the GaAs and the GaAlAs, which causes a lower back interface potential barrier, decreasing the amount of high-energy photoelectrons. (C) 2009 Optical Society of America

Study on the oxygen concentration reduction in heavily Sb-doped silicon

It was determined that oxygen concentration in heavily Sb-doped silicon was about 40% lower than that in the lightly doped Czochralski grown silicon and decreased with increasing content of Sb by means of coincident elastic recoil detection analysis. Through thermodynamic calculation, the oxygen loss by evaporation from the free surface of melt is only due to the formation of SiO, and Sb2O3 evaporation can be neglected. The basic reason for oxygen concentration reduction in heavily Sb-doped CZSi was that oxygen solubility decreased when element Sb with larger radius doped degenerately into silicon crystal. (C) 1999 Elsevier Science B.V. All rights reserved.

High-concentration hydrogen in unintentionally doped GaN

We use nuclear reaction analysis to study hydrogen in unintentionally doped GaN, and high-concentration hydrogen, nearly 10(21) cm(-3), is detected. Accordingly, a broad but intense infrared absorption zone with a peak at 2962 cm(-1) is reported, which is tentatively assigned to the stretch mode of NH: Ga complex. The complex is assumed to be one candidate answering for background electrons in unintentionally doped GaN. (C) 1998 Elsevier Science B.V. All rights reserved.

Effect of dopant concentration on photocatalytic activity of TiO2 film doped by Mn non-uniformly

The thin films of TiO2 doped by Mn non-uniformly were prepared by sol-gel method under process control. In our preceding study, we investigated in detail, the effect of doping mode on the photocatalytic activity of TiO2 films showing that Mn non-uniform doping can greatly enhance the activity. In this study we looked at the effect of doping concentration on the photocatalytic activity of the TiO2 films. In this paper, the thin films were characterized by UV-vis spectrophotometer and electrochemical workstation. The activity of the photocatalyst was also evaluated by photocatalytic degradation rate of aqueous methyl orange under UV radiation. The results illustrate that the TiO2 thin film doped by Mn non-uniformly at the optimal dopant concentration (0.7 at %) is of the highest activity, and on the contrary, the activity of those doped uniformly is decreased. As a comparison, in 80 min, the degradation rate of methyl orange is 62 %, 12 % and 34 % for Mn non-uniform doping film (0.7 at %), the uniform doping film (0.7 at %) and pure titanium dioxide film, respectively. We have seen that, for the doping and the pure TiO2 films, the stronger signals of open circuit potential and transient photocurrent, the better photocatalytic activity. We also discusse the effect of dopant concentration on the photocatalytic activity of the TiO2 films in terms of effective separation of the photon-generated carriers in the semiconductor. (C) Versita Warsaw and Springer-Verlag Berlin Heidelberg. All rights reserved.

Modeling and optimizing of high-concentration erbium-doped fiber amplifiers with consideration of ion-clusters

Starting from the modeling of isolated ions and ion-clusters, a closed form rate and power evolution equations for high-concentration erbium-doped fiber amplifiers are constructed. Based on the equations, the effects of the fraction of ion-clusters in total ions and the number of ions per cluster on the performance of high-concentration erbium-doped fiber amplifiers are analyzed numerically. The results show that the presence of the ion-clusters deteriorates amplifier performance, such as the signal power, signal gain, the threshold pump power for zero gain, saturated signal gain, and the maximum gain efficiency, etc. The optimum fiber length or other parameters should be modified with the ion-clusters being taken into account for the amplifiers to achieve a better performance. (c) 2007 Elsevier B.V. All rights reserved.

Formation and Properties of a Novel Heavy-Metal Chalcogenide Glass Doped with a High Dysprosium Concentration

A novel heavy-metal chalcogenide glass doped with a high dysprosium ion (Dy(3+)) concentration was prepared by the well-established melt-quenching technique from high-purity elements. The results show that when Cadmium (Cd) is introduced into chalcogenide glass, the concentration of Dy(3+) ions doped in GeGaCdS glasses is markedly increased, the thermodynamic performance improves, and the difference between T(g) and T(x) is >120 degrees C. The Vickers microhardness is also modified greatly, about 245 kgf/mm(2). The optical spectra indicate that all absorption and emission bands of Dy(3+) are clearly observed and red-shifted with increasing Dy(3+) concentration.