最新刊期
卷 34 ， 期 7 ， 2013
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Optical Properties of ZnxCd1-xSe/MgSe Quantum Wells Grown on InP Substrate by Molecular Beam Epitaxy
摘要：We studied the band gap structure of ZnxCd1-xSe/MgSe heterostructure grown on (001) InP substrates by molecular beam epitaxy. In the single quantum well growth of ZnxCd1-xSe/MgSe, the in situ reflection high energy electron diffraction intensity oscillations and streak patterns demonstrate that zincblende (ZB) MgSe has been formed. Furthermore, with the introduction of thick ZnxCd1-xSe spacer layers, the ZB MgSe/ZnxCd1-xSe multi-quantum wells can be obtained. Based on the results of photoluminescence and calculation, the offset for conduction and valence band in MgSe/ZnxCd1-xSe heterostructure is estimated to be 1.2 eV and 0.27 eV, respectively. Using the estimated value of band offset, the calculated ISB transition energies agree well with results of infrared absorption experiments. With such a large band offset, ISB transitions in this material system could be extended to 1.55 μm within an asymmetric double quantum wells with coupling effects.关键词：molecular beam epitaxy;Ⅱ-Ⅵ quantum wells;zincblende MgSe;band offset95|124|0更新时间：2020-08-12 - 摘要：A metal complex[(4m2pq)2Ir(acac)] was synthesized under mild condition of dichloromethane as solvent and potassium carbonate as deacid reagent at 25℃, where "4m2pq" is the ortho-C-deprotonated derived from 4-methyl-2-phenylquinoline and "acac" is derived from pentane-2,4-dione. The molecular structure of (4m2pq)2Ir(acac) was characterized by 1H NMR spectral,13C NMR spectrum and X-ray diffraction. UV-visible absorption spectrum, photoluminescence spectrum, luminescence quantum yields and phosphorescence lifetime were measured for studying photophysical properties of (4m2pq)2Ir(acac). The single crystal structure of (4m2pq)2Ir(acac) is in triclinic and space group P1. The orange phosphorescent emission with high fluorescence quantum efficiencies of 50.4% and lifetime of 0.33 μs can be observed with peaks at 597 nm in degassed CH2Cl2 solution at room temperature. Moreover, (4m2pq)2Ir(acac) was utilized as phosphorescence dopant in OLEDs with the structures of ITO/NPB (30 nm)/CBP:(4m2pq)2Ir(acac) (mass fraction of 6% and 8%, 20 nm)/BCP (10 nm)/Alq3 (20 nm)/LiF (1 nm)/Al. The device showed orange emission at 597 nm, maximum brightness of 39 667 cd/m2, current efficiency of 14.2 cd/A, and power efficiency of 8.1 lm/W.182|139|1更新时间：2020-08-12
- 摘要：NaYS2:0.20Yb3+, 0.03Er3+ and NaYS2:0.03Er3+ powder samples were synthesized with solid-state reacting methods, respectively. The Stocks and Anti-Stocks light-emitting properties with Er3+ were researched. Dependences of the emission features on excited population processes were exhibited with the spectra obtained following an excitation, respectively, at 980, 532 and 408 nm. Effects of local field of doped Re3+ (Re3+ standing for Yb3+ or Er3+) on S2-Re3+ charge transfer state (CTS) were observed. Further, the energy-transfer processes between Yb3+ and Er3+ based on the energy matching conditions and the Stocks and Anti-Stocks emission mechanism with Er3+ should be suggested with schematic energy-level schemes.关键词：rare earths;Stocks and Anti-Stocks transition;CTS117|120|1更新时间：2020-08-12
- 摘要：3-Mercaptopropionic acid capped CdTe quantum dots (QDs) were synthesized in aqueous solution under nitrogen protection. The samples were characterized by photoluminescence (PL) spectroscopy, Ultraviolet-Visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. The XRD result show that CdTe QDs have a cubic zinc-blende structure, and the TEM result show that CdTe QDs are spherical with good dispersibility. The effects of reflux time, reflux temperature and pH on the property of QDs were studied. Experimental results show that reflux time, reflux temperature and pH can influence the particle size, size distribution and the rate of growth. The obtained CdTe QDs are water-soluble and have fluorescence sensitivity to Ni2+ ions,thus CdTe QDs can be used as the fluorescent probe to investigate Ni2+ ion in water.关键词：CdTe;QDs;fluorescent probe157|505|7更新时间：2020-08-12
- 摘要：SrMgAl10O17:Eu2+ blue phosphor was obtained by one-step calcination process of precursor synthesized by the co-precipitation method. Eu2O3(AR), Sr(NO3)2(AR), Mg(NO3)2·6H2O(AR), Al(NO3)3·9H2O(AR) were used as raw materials and NH4HCO3 was as precipitating agent. The crystal structure and luminescent properties of the samples were analyzed by the X-ray diffraction and the fluorescence spectrophotometer. The results show that the calcination temperature can be dropped to 1 200℃, which is 300℃ lower than the temperature of high temperature solid state reaction. The peak of emission wavelength of SrMgAl10O17:Eu2+ is at 470 nm. The optimum mole fraction of Eu2+ is 10%. H3BO3 was chosen as fluxes agent, and the optimum mass fraction is 1.5%.关键词：co-precipitation;one-step calcination process;SrMgAl10O17：Eu2+ phosphor;fluxes agent99|122|0更新时间：2020-08-12
- 摘要：Carbon nanotubes (CNTs) fabricated by thermal chemical vapor deposition (T-CVD) on GaAs microtips were investigate. Scanning electron microscope and Raman spectrum were used to characterize the properties of the nanotubes. The results showed that the GaAs tips changed into ladder-like array at high temperature and carbon nanotubes connected the neighbor GaAs with high graphite microcrystal structure. A model for the CNTs grown on GaAs microtips was also proposed. The results presented here make a significant step to the connection for micro or nano devices.关键词：carbon nanotubes;T-CVD;GaAs;liquid phase epitaxy86|192|0更新时间：2020-08-12
- 摘要：Semiconducting polymer CN-PPV nanoparticles (NPs) were prepared by the reprecipitation method and further encapsulated by a facile method. The particle size and the distribution were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The average diameter is ~30 nm for bare CN-PPV nanopartilces and ~60 nm for encapsulated ones. UV-Vis and fluorescence spectroscopy showed consistent results between CN-PPV and SiO2/CN-PPV nanoparticles. More importantly, silica capsulation improved the photostablility of CN-PPV nanoparticles, and provided reliable surface for covalent conjugation with biomolecules. These photostable nanoprobes are promising for biomedical imaging applications.关键词：conjugated polymer;nanoparticles;encapsulation;silica;fluorescence121|118|0更新时间：2020-08-12
- 摘要：Er3+,Yb3+ co-doped NaGd(MoO4)2 phosphors were synthesized via solid-state reaction method. Their structures were investigated with X-ray diffraction at first,and the down-conversion and up-conversion properties of the phosphors were investigated as well. On one hand, it is confirmed that the excitation energy can be effectively transferred from host lattice to luminescent centers, Er3+, upon analyzing excitation spectrum and emission spectrum. On the other hand, it is found, from the up-conversion luminescent spectrum, that the two-photon process is responsible for both red and green up-conversion emissions in the samples of wide range of Yb3+ concentrations. In addition the effect of LD pump current and dopant concentrations on up-conversion luminescence intensity were studied. Finally, the mechanism of up-converting luminescence was interpreted.关键词：up-conversion;solid-state reaction method;NaGd(MoO4)2;energy transfer141|115|4更新时间：2020-08-12
- 摘要：The lamp used green (Ce0.67,Tb0.33)MgAl11O19 phosphor was synthesized by the flux method using different fluxes, and the luminescent properties of obtained samples were investigated in details. The influence of single flux and multi-fluxes on the brightness and morphology of particles was also studied. It is found that the optimal components of the multi-fluxes is 0.2%H3BO3+2.0%Li2CO3+2.0%AlF3 (mass fraction). The particles of optimal (Ce0.67,Tb0.33)MgAl11O19 sample have regular and uniform morphology, and the rate of brightness of this sample to present commercial (Ce0.67,Tb0.33)MgAl11O19 phosphor is about 103:100.关键词：(Ce0.67;Tb0.33)MgAl11O19;flux method;phosphor114|82|0更新时间：2020-08-12
- 摘要：Using C19H42BrN as surfactant, ZnS:Mn nanocrystallines were synthesized by hydrothermal method. The phase, size and luminescent properties of the nanocrystals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and fluorescence photometer. The results show that ZnS:Mn nanocrystals are 4~8 nm of particle size and have a cubic zinc blend crystal structure. The fluorescence spectra showed that the emission peak increased with the increment of Mn-doped concentration and the increment of surfactant.关键词：ZnS：Mn;nanocrystalline;ion doping;hydrothermal method;photoluminescent property93|253|3更新时间：2020-08-12
- 摘要：Yb3+ and Ho3+ codoped BaGd2ZnO5 phosphors were synthesized by using the sol-gel method. The upconversion emission spectra of BaGd2ZnO5:Yb3+, Ho3+ phosphors were measured under the excitation of 971 nm LD laser at different excitation density. Under the excitation of 971 nm LD laser modulated by a square wave signal, the excited and decay processes of green upconversion luminescence in Yb3+/Ho3+ codoped BaGd2ZnO5 were observed by an oscilloscope. The rate equations of energy level 5F4(5S2),5I6 with Ho3+ ion and energy level 2F5/2 with Yb3+ ion were built to analyze the upconversion mechanism in Yb3+/Ho3+ codoped system, then the rate equation of the energy level 5F4(5S2) with Ho3+ ion was used to fit this processe in order to determine the lifetime of the energy levels. When excitation is steady, the population of 5F4(5S2) energy level with Ho3+ ion mainly come from the energy transfer from Yb3+ to Ho3+, and the effect of excited state absorption was able to be ignored.关键词：upconversion;Yb3+/Ho3+;BaGd2ZnO5;green upconversion emission96|135|1更新时间：2020-08-12
- 摘要：We report a dramatic increase in the internal quantum efficiency (IQE) of ZnO/ZnMgO multi-quantum wells (MQWs) fabricated on c-plane sapphire substrate by introducing asymmetric double-quantum-well (ADQW) structure. A marked enhancement in efficiency, by as much as 1.56 times, was observed for the ZnO/ZnMgO five-period ADQW grown by plasma-assisted molecular beam epitaxy (P-MBE), compared to the ten-period symmetrical MQWs with asymmetric structure. The effects of excitons tunneling from the narrow well to the wide well, which was proved by photoluminescence spectra and time-resolved photoluminescence spectroscopy, can influence the IQE.关键词：ZnO;quantum wells;excitons tunneling;internal quantum efficiency97|180|1更新时间：2020-08-12
- 摘要：Red and green phosphorescent organic light emitting diodes were fabricated, utilizing GIr1 and R-4B (novel red and green) phosphorescent materials. Device structure was ITO/MoO3(50 nm)/NPB(40 nm)/TCTA(10 nm)/CBP:14%GIr1(30 nm)/TCTA(x)/CBP:2%R-4B(10 nm)/BCP(10 nm)/Alq3 (40 nm)/LiF(1 nm)/Al(100 nm). The luminescent properties were studied by inserting different thickness of TCTA (regulation of carrier) spacer layer between red and green emitting layer to adjust the distribution of carriers and excitons. The results showed that the optimum performance of OLED was achieved when the thickness of TCTA spacer layer is 1 nm. The maximum the device performance reached 13.72 cd/A, 0.509 mA/cm2 and 69.91 cd/m2 at 6 V. While for 0 nm (none spacer), the device performance reached 11.67 cd/A, 1.848 mA/cm2 and 215.7 cd/m2 at 6 V.关键词：organic light emitting diodes;phosphorescence;blocking layer;spacer111|148|0更新时间：2020-08-12
- 摘要：An abnormal jump of emission current was observed in a single wall carbon nanotube (SWCNT) rope field emitter, in which two soda-lime glass flakes were set on both sides of SWCNT rope. It gave rise of an apparent enhancement of the emission current after the jump. All these peculiar characteristics of field emission were attributed to the modification of electric field at the presence of glass flakes and its contribution to the selective divergence of electron trajectories. Theoretic analysis and subsequently evidential investigations were carried out to certify the influence of the dimension, separation distance and dielectric constant of the dielectric medium on the I-V characteristics of SWCNT rope, which suggests a feasible way to control the field emission properties from Spindt-type emitters including CNT rope.关键词：carbon nanotube;field emission;trajectory;dielectric84|111|0更新时间：2020-08-12
- 摘要：A three-layered near-infrared OLED with structure of ITO/PEDOT:PSS/PVK/neodymium tris-(8-hydroxyquinoline) (Ndq3)/Al was fabricated, in which poly(N-vinylcarbazole) (PVK) was hole transport layer, and poly(3, 4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) was hole injection layer. The EL spectrum shows three emission peaks at 905, 1 064, 1 340 nm in the near-infrared range which are correspond to Nd3+ transitions of 4F3/2→4I9/2, 4F3/2→4I11/2, 4F3/2→4I13/2, respectively. The influence mechanism of functional layers was discussed with help of I-V curves, in reference with single layer device (ITO/Ndq3/Al) and double layer device (ITO/PVK/Ndq3/Al). The increase in device current corresponding to the reduction of the series resistance was observed and was related to the high conductivity of PEDOT:PSS layer. The joint action on the hole injection barrier by PVK and PEDOT:PSS was contributed to the improvement of the charge carriers balance of device and EL emission intensity. Also, the decrease of the ITO surface roughness was realized as one of the key issue for the performance improvement.关键词：near-infrared light emitting diode;hole injection layer;hole transport layer;neodymium tris-(8-hydroxyquinoline)114|78|1更新时间：2020-08-12
- 摘要：CdSe/CdS/ZnS quantum dots were synthesized in oil phase. Comparing with the CdSe quantum dots, the absorption-peaks and PL-peaks wavelengths of the CdSe/CdS/ZnS quantum dots had a red shifted. By using the COMSOL software, the electric field distribution of the CdSe/CdS/ZnS doped fiber and toluene doped fiber were simulated. The results show that the electric field intensity of the CdSe/CdS/ZnS quantum dots doped fiber is higher than that of the toluene one. The signal voltage value of the toluene doped fiber, CdSe/ZnS quantum dots doped fiber, and CdSe/CdS/ZnS quantum dots doped fiber were measured by 532 nm CW laser. The results demonstrate that the signal voltage value of the CdSe/ZnS and the CdSe/CdS/ZnS quantum dots doped fibers are enhanced to 6.28 mV and 18.43 mV, respectively. It shows that the gain of CdSe/CdS/ZnS quantum dots doped fiber is higher than that of the CdSe/ZnS one. So, the CdSe/CdS/ZnS quantum dots are more suitable for fiber signal transmission as gain medium in the future.关键词：fiber optics;quantum dots;red shift;spectroscopic analysis;gain133|156|0更新时间：2020-08-12
- 摘要：In recent years, all-solid-state passively Q-switched laser technology gets a rapid progress in obtaining picosecond pulses. Comparing with mode-locked lasers with complicated structure, sensitive and difficult alignment, these Q-switched picosecond lasers show great practical potentials for their characters of low cost, simple structure and easy alignment. These Q-switched lasers can provide picosecond pulses with considerable energy, and with the advantage of adjustable pulse repetition rate. In this paper, two existing passively Q-switched picosecond laser approaches, namely, Cr:YAG microchip lasers, semiconductor saturable absorber mirror(SESAM) microchip lasers, are discussed accompany with the consideration of further treatment to the latter one by nonlinear optical processing and amplification, which are introduced to get narrower pulse width and higher pulse energy. In two categories, we review remarkable work in this field along with breakthroughs of them.关键词：all solid-state;passively Q-switching;picosecond laser technology;microchip laser technology;nonlinear optics technology156|99|3更新时间：2020-08-12
- 摘要：The software simulation and theoretical calculations are used to analysis the relationship between InxGa1-xN quantum well blue LED's photoelectric properties and quantum well bound state energy level. A bound state split level model is established. When the quantum well thickness is narrower, the band bending caused by the polarization effects is the main reason for the spectral red-shift, and electron leakage is the main reason for efficiency droop. But as the well width increase, level filling is the main reason for the red-shift of spectrum, Auger recombination and carrier delocalization are the main reason for lower efficiency. By this article, the optimization quantum well width for InGaN/GaN light-emitting diodes can be obtained. The maximum internal quantum efficiency and luminous efficiency can be obtained when the optimization quantum well width is 2.5~3.5 nm.关键词：width of quantum well;efficiency droop;numerical simulate;InGaN/GaN LED89|40|0更新时间：2020-08-12
- 摘要：InGaN/GaN multiple-quantum well (MQW) light-emitting diodes (LEDs) were fabricated, in which a SiO2 current blocking layer (CBL) was inserted underneath the p-pad electrode. Samples were divided into three groups: normal surface, surface roughing, and surface roughing plus side wall etching. Each group had two different structure devices: with and without CBL. In each group, the voltage Vf at 20 mA for the LEDs with a CBL (Vf=3.156, 3.282, 3.284 V) were slightly higher than those of without CBL (Vf=3.105, 3.205, 3.210 V). However, the luminous efficiency and the light-output power of the LEDs with CBL were better than those without CBL. At 20 mA current, the output power of the LEDs with a CBL increase 10.20%, 12.19%, 11.49% compared with those without CBL. It is due to the current spreading effect in CBL devices. The CBL can also reduce parasitic optical absorption in the p-pad electrode.关键词：LED;CBL;light-output power;luminous efficiency86|113|0更新时间：2020-08-12
- 摘要：In order to fast acquire the gamut boundary of a LED display panel, an iterative method was proposed for the calculation of intersections between mapping lines and the gamut boundary, which was further used to get the fitting gamut boundary in each hue plane. Firstly, the judgment method if a color was in the LED display panel color gamut was supplied based on the colorimetric principles of LED display. And then, in the CIELAB uniform color space, it analyzed the iteration principle, determined the initial values for iteration, and carried out the analysis of calculation precision and speed. Finally, with D65 as reference, a LED display panel boundary fitting experiment and its color difference analysis were carried out in the same hue plane. Experiment result shows that the fitting boundary is very smooth after 11 iterations, and the maximum color difference between the true value and calculated value of the gamut boundary point on every mapping line is only 0.23. Compared with the interpolation methods, the maximum color difference is decreased and calculation speed is increased by an order of magnitude respectively. The method suggested could meet the needs of gamut analysis and gamut mapping with other display devices for the LED display panel in both the calculation precision and speed.关键词：LED display panel;color gamut boundary;iteration algorithm129|594|8更新时间：2020-08-12
- 摘要：In Tris-HCl buffer solution(pH=7.40), the reaction between bovine serum albumin (BSA) and Glipizide can lead the fluorescence of BSA quenching regularly. Based on this pheno-menon, a new method that determining the content of Glipizide was established, in which BSA was used as the fluorescent probe. The concentration of Glipizide presented a nice liner relation with the fluorescence intensity from 0.25 to 20 μmol/L. The detection limit was 0.071 μmol/L. The method was applied to analysis the Glipizide content in drugs samples, and the RSD was from 1.29% to 2.80%, the recovery rate was from 86.79% to 96.43% with six parallel determinations.关键词：bovine serum albumin;glipizide;fluorescent probe;content determination79|209|1更新时间：2020-08-12
- 摘要：We fabricated a subwavelength metallic grating using nanoimprint technology and mea-sured the reflection spectrum using ultraviolet-visible-near-infrared spectrophotometer. Based on the theory of conventional rigorous coupled wave analysis, we used a new method to analyze the diffraction problems of subwavelength metallic gratings. We used fast Fourier factorization (FFF) method to derive the coupled wave equations, then each space harmonic can be expanded in terms of Legendre polynomials in grating region. Using this modified vector diffraction theory, we calculated the diffraction efficiency and the field distribution. All calculated results show great agreement with the experimental results.关键词：subwavelength metallic gratings;nanoimprint;surface plasmon360|81|3更新时间：2020-08-12
- 摘要：In order to convert elliptical Gaussian laser beam to circle flat-top beam, a two-mirror unobscured reflective optical system is designed. Based on the energy conservation law, the Flattened Lorentzian function is chosen as the distribution expression of the output flat-top beam to build the relationship between the input and output aperture coordinates. The equations in integral form that describe the reflective surfaces of the shaping system are derived by applying the law of reflection expressed in vector. Through the numerical calculation of the surface data and optical design software simulation, the circle flat-top collimated output beam is achieved and the illumination uniformity of the target area is above 95%. It indicates that the shaping system could improve the flatten degree of the elliptical Gaussian laser beam apparently.关键词：laser beam shaping;elliptical Gaussian beam;flat-top beam;reflective system161|232|3更新时间：2020-08-12
- 摘要：A polymer waveguide sensor was designed based on the theory of surface plasmon resonance (SPR). The sensor with SU-8 polymer as the waveguide core material is fabricated on a silicon substrate with a under cladding layer of PMMA. Effect of refractive index of polymer, refractive index of analyte, the different metal, and the thickness of metal on SPR curve is analyzed. Theoretical analysis results show that the sensor sensitivity is improved with the refractive index of analyte increase. The resonance wavelengths of SPR sensor move to longwave direction when the refractive index of polymer is low, and its detection range trend to move to long refractive index. Otherwise the results are contrary.关键词：polymer waveguide sensor;surface plasmon resonance;index of refraction128|207|5更新时间：2020-08-12
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