最新刊期
卷 32 ， 期 12 ， 2011
- 摘要：One-dimensional ZnO nanoshuttles were synthesized on Si substrates by a hydrothermal method at 90 ℃ for 24 h using hexamethyenetetramine(HMT) and zinc nitrate as raw materials. The morphology and crystal structure were characterized by field-emission scanning electron microscopy, X-ray diffraction, and high resolution transmission electron microscope. All the data indicated that ZnO nanoshuttles are homogeneous in morphology and uniform in size, with a single-crystal hexagonal wurtzite structure and acceptable crystal quality. Room-temperature photoluminescent spectra showed that a strong near-bang-edge UV emission peak and a much weak defect emission, which suggested that ZnO nanoshuttles have a good optical quality. The nucleation and growth mechanism in the reaction process of ZnO nanoshuttles were also discussed in this work.关键词：ZnO nanoshuttle;hydrothermal method;optical properties;growth mechanism102|279|1更新时间：2020-08-12
- 摘要：Red phosphors of Eu3+ and Bi3+ single- and double- doped LaMgB5O10 have been synthesized by a solid-state reaction. The red emission intensities were enhanced with the increase of Bi2O3 content. The crystal structures were analyzed using the X-ray diffraction. It indicated that the crystallization is better in the codoped samples than the Eu3+ monodoped sample. According to the results calculated by the Judd-Ofelt theory, the internal quantum efficiencies keep a constant value of about 43%. Moreover, red emission intensity increase 50% in the codoped sample comparison with the Eu3+ monodoped one under 394 nm excitation. It was confirmed that the enhanced red photoluminescence is due to the increase of Eu3+absorption strengths.关键词：LaMgB5O10;Judd-Ofelt theory;enhanced red photoluminescence119|156|2更新时间：2020-08-12
- 摘要：The photoluminescence spectra of K2GdF5:Tb3+(0.5%, mole fraction) single crystal under various excitations were measured and compared. The room temperature excitation spectra of 5D3→7F6 and 5D4→7F5 transitions exhibited three broad bands and three groups of narrow peaks. The narrow peaks were assigned as 8S7/2→6FJ6GJ, 8S7/2→6DJ and 8S7/2→6IJ transition of Gd3+ and the broad bands were assigned as the absorption from the ground state 7F6 to the low-spin states of 4f7(8S)5d configurations of Tb3+. The mechanism of energy transfer from Gd3+ to Tb3+ and the cross relaxation between Tb3+ ions were also analyzed.关键词：K2GdF5;Tb3+;VUV;energy transfer;cross relaxation102|107|0更新时间：2020-08-12
- 摘要：Erbium-doped fiber amplifier (EDFA), utilizing the emission transition 4I13/2→4I15/2 of Er3+, is a key element of the 1.5 μm window telecommunication system. In recent years, in order to raise amplifier gain parameters, many solutions, such as Er3+/Yb3+, Er3+/Eu3+, Er3+/Sm3+-doped, were introduced. In this paper, novel Er3+-doped and Er3+/Yb3+co-doped TeO2-Bi2O3-SiO2-B2O3 glass were prepared by high-temperature melt-quenching method. The absorption spectra and emission spectra of Er3+- doped glass, the emission spectra and lifetimes of Er3+/Yb3+co-doped glass were measured and investigated. The intensity parameters Ωt (t=2,4,6) were calculated by using the theory of Judd-Ofelt. Under 808 nm semiconductor laser excitation, the infrared emission intensity ratio of Yb3+ ions to Er3+ ions and mechanism of counter energy transfer were discussed in Er3+/Yb3+co-doped glass. The results indicate that a maximum value of full width half maximum (FWHM) of 1.53 μm infrared emission spectra is 90 nm in Er3+-doped glasses, and the suitable content of Yb3+ ions is helpful for decreasing the disappearing population velocity of Er3+:4I13/2 level, increasing the emission intensity of Er3+:4I13/2→4I15/2 transition and lifetime of Er3+:4I13/2 level.关键词：Er3+/ Yb3+ co-doped;tellurite glass;infrared emission;counter energy transfer130|139|1更新时间：2020-08-12
- 摘要：NaYF4∶Yb3+, Er3+ nanoparticles with the size about 40 nm were successfully prepared by the combination of coprecipitation and hydrothermal methods using trisodium citrate as chelator. The obtained sample was divided into two parts, one of them was annealed in nitrogen at 300 ℃ for 2 h. The crystal structure of the NaYF4∶Yb3+, Er3+ nanoparticles before and after annealing treatment are in cubic phase, the size of which is about 40 nm. Under the excitation of 980 nm laser, the total upconversion luminescence intensity and the relative green emission intensity of the sample after annealing is much stronger than that of the sample without annealing treatment. It is found that high temperature annealing improved the crystallization of the sample and reduced the concentration of the organic molecules on the surface of the nanoparticles, resulting in a great improve of the upconversion luminescence property.关键词：nanocrystals;upconversion;rare earth;annealing137|69|1更新时间：2020-08-12
- 摘要：The up-conversion NaGdF4∶Yb3+,Ho3+ and GdF3∶Yb3+,Ho3+ nanocrystals were successfully prepared by hydrothermal method. The samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and luminescence spectra. The crystal structure and morphology can be well controlled by adjusting the molar ratio of n(F-)∶n(Ln3+),the value of pH and the molar ratio of n(Citrate)∶n(Ln). The hexagonal NaGdF4∶Yb3+,Ho3+ and GdF3∶Yb3+,Ho3+ samples exhibit green(541 nm)and red(647 nm)emissions under 980 nm excitation, which are assigned to the transition of 5F4,5S2→5I8 and 5F5→5I8 in Ho3+,respectively. It was found that the upconversion efficiency of the hexagonal prism and flake NaGdF4∶Yb3+,Ho3+ samples are much stronger than that of GdF3∶Yb3+,Ho3+ samples, but the spherical NaGdF4∶Yb3+,Ho3+ samples are weaker than GdF3∶Yb3+,Ho3+ samples. This indicates that the upconversion efficiency of hexagonal NaGdF4∶Yb3+,Ho3+ samples are greatly impacted by the different size and crystalline for different morphology.关键词：NaGdF4∶Yb3+;Ho3+;GdF3∶Yb3+;morphology controlled;upconversion emission121|45|2更新时间：2020-08-12
- 摘要：Tb3+ doped Gd2(MoO4)3 phosphors were prepared by using MoO3, Gd2O3 and Tb4O7 as starting materials via a solid state reaction with flux of NH4HF2. The X-ray diffraction was used to characterize the crystal structure of the final resultants. It was found that the products exist in orthorhombic phase with space group Pba2. Excitation and emission spectra indicated that the studied phosphors can absorb 200~300 nm lights, which corresponding to both the f-d and Mo-O transitions, and emit blue broad band and green narrow lines originate from MoO42- and f-f transitions, respectively. Meanwhile, the concentration quenching and fluorescence decays were also studied, and it was found that in the case of taking carbon powder as reductant, Tb4O7 can not be well reduced. The color coordinates for the phosphors various with Tb3+ concentrations, and that the color purity for the phosphors are not good. From the obtained results, it can be concluded that this phosphor is not a promising one for the practical applications.关键词：Gd2(MoO4)3;Tb3+;green emitting phosphor;fluorescence decay108|72|6更新时间：2020-08-12
- 摘要：ZnAl2O4 composite structure was fabricated using Zn and C powers by CVD method at different temperature. Structure and optical properties of the composite structure were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). SEM results indicated that the sample of ZnAl2O4 structure prepared at 800 ℃ remained the regular pore structure of AAO template. The XRD patterns demonstrated that the diffraction peaks of the ZnAl2O4 appeared at the reaction temperature of 700, 800, 900 ℃. That indicated the ZnAl2O4 structures were obtained successfully. The optimum temperature for CVD method fabricated ZnAl2O4 nanostructure was 800 ℃ by the SEM and XRD results.关键词：spinel-type ZnAl2O4;AAO/Si template;chemical vapor deposition135|66|0更新时间：2020-08-12
- 摘要：Zn1-xMnxO thin films were successfully grown on Si (111) substrates by pulsed laser deposition (PLD). X-ray diffraction measurement revealed that all the films were single phase and had wurtzite structure with c-axis orientation. As Mn concentration increased in Zn1-xMnxO films, the c-axis lattice constant increased gradually. Atomic Force Microscopy (AFM) showed that surface roughness and morphology changed with doping concentrations. Photoluminescence spectra of Zn1-xMnxO thin films were also studied which shows a narrow UV band at 387 nm, a broad blue band of 430 nm and another broad peak at 545 nm. It was deduced that Mn doping leads to a blue shift of the UV band, and a red shift of 430 nm and 545 nm.关键词：X-ray diffraction;photoluminescence;Mn-doped ZnO thin films;PLD134|82|2更新时间：2020-08-12
- 摘要：Calcium silicate glass-ceramic phosphor with green emission was evaluated.The effect of crystals precipitation microstructure on spectral properties was investigated by changing the holding time at melting temperature. With the in crease of holding duration, the amount ratio of luminous β-Ca2SiO4∶Eu2+ crystalline phase to glassy phase tended to be decreased, leading to a red-shift of the emission band and exhibiting more transparent of the glass-ceramic phosphor. The precipitation of SiO2 crystals in priority was proposed. The broad excitation band of the green-emitting glass-ceramic phosphors covers the wavelength from 270 to 440 nm, showing the potential for the high-power phosphor-converted LED.关键词：glass-ceramic phosphors;bulk crystallization;β-Ca2SiO4∶Eu2+113|87|0更新时间：2020-08-12
- 摘要：A white light microcavity organic light-emitting device (WOLED) was fabricated and characterized. Design method of WOLED has been studied.This microcavity has two color matched cavity modes structure and a wide band green organic luminous material. Comparing with the normal structural OLED, EL efficiency of microcavity WOLED was improved by 0.7 times. Optimized microcavity structure can lead to a color coordinator of (0.34, 0.33). The CIE of microcavity OLED was stable at different volatge. Further study should focus on multi mode cavity structure for optimizing color rendering index.关键词：microcavity;white light;organic light-emitting device;structure design119|91|0更新时间：2020-08-12
- 摘要：Exciplex emission is considered to be very important for understanding the fundamental processes of electronic excitation. Here we report a pure exciplex emission device of the binary-blend ITO/ Poly(3,4-ethylenedioxythiophene)∶poly (styrenesulfonate) (PEDOT∶PSS)/poly [-bis (4-butylphenyl)-bis(phenyl) benzidine](Poly-TPD)∶2,5-bis(5-tert-butyl-2-benzoxazolyl) thiophene (BBOT)/Al. The luminance-voltage and current density-voltage characteristics of devices were investigated, and differences between their performances were discussed. The pure exciplex electroluminescence was investigated in terms of the energy level diagram of the Poly-TPD∶BBOT device.关键词：green-yellow emission;organic light emitting devices;Poly-TPD∶BBOT111|170|1更新时间：2020-08-12
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Enhanced Performance of Small Molecular Weight Organic Solar Cells by Incorporating Ag Nanoparticles
摘要：Enhanced performance of small molecular weight organic solar cells based on CuPc/C60 and TiOPc/C60 with Ag nanoparticles fabricated on the ITO anode and MoO3 as the anode buffer layer has been demonstrated. Surface plasmon induced by the incorporation of Ag nanoparticles results in the increased absorption efficiency and photogenerated exciton dissociation probability of the photoactive layers. Meanwhile, the quenching of the photogenerated excitons at the organic/metal interface can be successfully restricted by the MoO3 anode buffer layer. Consequently, the short-circuit current is improved and the other parameters maintain unaffected, which leads to an enhanced power conversion efficiency of the devices.关键词：organic solar cell;Ag nanoparticle;surface plasmon;MoO3125|138|1更新时间：2020-08-12 - 摘要：Contact properties between electrodes and organic layers play a key role for the performance of an organic device. Ohmic contacts at electrode/organic interfaces are required for an ideal device. In order to improve performance of 4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl (DPVBi, a typical blue organic luminescent material) based organic light-emitting diode, MoO3 was introduced at anode interface as a buffer layer and a highly efficient bright nondoped blue electroluminescent device with low driving voltage was fabricated. Luminescent efficiency of the device with a 0.5-nm-thick MoO3 buffer layer is 18 times higher than that of the device without buffer layer, and 1.2 times higher than that of the device with a conventional copper phthalocyanine (CuPc) buffer layer at a current density of 20 mA/cm2. Turn-on voltage, maximum external quantum efficiency and luminance of the device are 3.3 V, 3.1% and 16000 cd/m2, respectively. Commission Internationale de l'Eclairage (CIE) co-ordinates are (0.15, 0.15). Realization of excellent device performance is attributed to formation of ohmic contact between anode and organics by insertion of MoO3.89|98|2更新时间：2020-08-12
- 摘要：Dry etching of InP material based on inductivity coupled plasma(ICP) was thoroughly studied, Cl2/Ar/H2 gas mixture was adopted, and the etching depth could reach 10 μm with a vertical and a smooth surface. The gas percentages of the total gas versus etching rate, and the applicable regions of Ni, SiO2, and the combination of Ni and SiO2 were studied, respectively. The regions of the effective etching rate and selectivity against Ni are 450~1200 nm/min and 175~190,respectively. The choosing and fabrication approaches adopted are highly suitable for any semiconductor material based on ICP system.关键词：hard mask;inductivity coupled plasma;InP;dry etching121|481|0更新时间：2020-08-12
- 摘要：The bottom gate thin-film transistors (TFTs) with un-annealed and annealed ZnO film as a channel layer were fabricated. Compared with the un-annealed device, the performance of the device with annealed ZnO had been improved. The saturation mobility increased from 2.3 to 3.12 cm2/(V·s), the threshold voltage reduced from 20.8 to 9.9 V, the threshold swing varied from 2.6 to 1.9 V/dec, and the threshold voltage shifted from 8.0 to 3.4 V after applying a gate bias stress of 25 V for 3 600 s. The experimental results indicate that using annealed ZnO film as channel layer is an effective approach for improving ZnO-based TFT performance and bias stress stability.关键词：thin-film transistor;ZnO;stability;annealing124|174|0更新时间：2020-08-12
- 摘要：We proposed an effective method to control the incident light power distribution ratio in each core of a core circular symmetrical distribution multi-core optical fiber. This method is realized by tapering the multi-core fiber to be a bi-tapered shape after fusing the multi-core fiber with a normal single mode fiber on the condition of core alignment. Based on the coupling theoretical model and analysis, the controlling method is introduced, and the results are demonstrated by both theory and experiment. Finally, this incident power distribution controlling method provides a helpful and potential application prospect for multi-core optical fibers devices and sensors.关键词：coupling characteristic;core-circular-symmetrical-distribution;optical multi-core fiber120|194|2更新时间：2020-08-12
- 摘要：The relationship between output power and reflectance of the cavity surface was simulated. Simulation results showed that, when the reflectance of cavity surface coatings took the optimum value, the output power of the semiconductor lasers diode reached the maximum. AlN film were deposited on K9 glass substrates by magnetron sputtering using high-purity Al target and N2+Ar. The influence of sputtering conditions, including working pressure, nitrogen concentration, sputtering power on its deposition rate and optical properties has been studied. The optimized AlN coating was used in semiconductor lasers, we found that the COD threshold and the output power have been greatly improved.关键词：AR film;refractivity;sputtering;COD133|328|3更新时间：2020-08-12
- 摘要：The MOCVD growth of AlxGa1-xAs for application in high-power laser diodes was studied by using time resolved reflectance anisotropy spectroscopy (RAS) and normalized reflectance (NR) were studied. Multi-layer AlxGa1-xAs structures with different Al compisition were grown on GaAs (001) substrates. The most suitable photon energy for monitoring the growth process was investigated. The NR and RAS signals at photon energy near the fundamental band gap showed an oscillatory behavior during the growth. The different contribution of surface-induced optical anisotropy and interface-induced optical anisotropy could be distinguished in situ by RAS transient spectra. The intensities of the RAS and NR signals were strongly dependent on the aluminium composition.关键词：epitaxial growth;metal-organic chemical vapor deposition;reflectance anisotropy spectroscopy118|125|0更新时间：2020-08-12
- 摘要：The polarization fluorescence spectra of isopropanol-water mixture excited by ultraviolet light was studied experimentally. The decay process of fluorescence intensity was detected at different center emission peaks. The curve was fitted by an exponential function and the processing data was obtained by deconvolution. Both the polarization degree and fluorescence lifetime were calculated, and mathematical characterization was performed for the fluorescence counts decay curves. The fluorescence emission and polarization characteristics were discussed. It is found that the isopropanol-water mixture excited by ultraviolet light obtains partially polarized fluorescence with certain molecular orientation. The polarization degree and anisotropy degree are 0.542 and 0.441, respectively. Induced by exciting light with wavelengths of 220 nm and 232 nm, the fluorescence lifetime of isopropanol-water mixture at peaks of 277, 284, 293,309 nm is about 17 ns. While the average fluorescence lifetime at peaks of 328 nm, 345 nm and 362 nm is around 21, 22, 16 ns, respectively. It is related with the molecular cluster structure relative stability of isopropanol-water mixture by the action of hydrogen bond. The research will contribute to the study of the molecular characteristic of isopropanol-water cluster.关键词：polarization spectrum;time resolved;fluorescence lifetime;isopropanol-water mixture126|180|0更新时间：2020-08-12
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