最新刊期
卷 32 ， 期 10 ， 2011
- 摘要：Annealing behavior for cubic-phase Mg0.57Zn0.43O thin films grown at 450 ℃ by metal-organic chemical vapor deposition were studied. After annealed at 550, 650, 750 and 850 ℃ in oxygen atmospheres, the crystal quality and surface smoothness of the thin films were improved significantly. Their bandgap shifts continuously to the higher energy the increasing annealing temperature. Confirmed by energy dispersive X-ray spectra, the enlarged bandgap was caused by the decrease of Zn content during annealing. Phase separation of the Mg0.57Zn0.43O films with significant surface roughening can also be observed during annealing at 950 ℃.关键词：MgZnO alloy;thermal annealing;surface morphology;grain size123|232|0更新时间：2020-08-12
- 摘要：Nitrogen-doped ZnO (ZnO∶N) films were grown by N-plasma assisted pulsed laser deposition. The p-type conductivities were achieved by post low-temperature rapid thermal annealing (RTA). The N chemical states, optical and electrical properties of ZnO∶N films were systematically studied by X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Hall measurements. The results revealed that the obtained p-type ZnO∶N films are highly compensated semiconductor, and the RTA process can activate more N acceptors and reduce the self-compensation of intrinsic donor defects. Three N acceptor-related emissions were observed in low-temperature PL spectra. The ionization energy of N acceptor was determined as about 128 meV from free-electron-to-acceptor (FA) transition. Interestingly, donor-acceptor pair (DAP) emission showed a slight redshift with increasing annealing temperature. This phenomenon was understood in terms of a potential fluctuation model.关键词：p-type;ZnO∶N films;PLD;optical and electrical properties131|1150|1更新时间：2020-08-12
- 摘要：A series of Sr3B2O6∶Eu3+, Na+ phosphors were synthesized at 1 200 ℃ by conventional solid state reaction method and their luminescent properties were investigated. Structural characterization of the luminescent materials was carried out with X-ray powder diffraction (XRD) analysis. XRD results showed that no apparently structure transformation of the Sr3B2O6 matrix was observed after doping appropriate amount of Eu3+, Na+. Photoluminescence spectra indicated that the phosphor can be efficiently excited by 394 nm near-UV light and exhibited an intense red luminescence corresponding to the electric dipole transition 5D0→7F2 at 615 nm. It was found that the optimal conditions to obtain the red emitting phosphor are 6% mole fraction of Eu3+, 3 h of the calcination time. In addition, the introduction of charge compensator Na+ can lead to the strongly enhanced emission intensity of Eu3+. Therefore, the material could be a promising red phosphor for possible applications in the white LED.关键词：Sr3B2O6∶Eu3+;Na+;solid-state reaction method;red emitting phosphor;white-LED118|92|9更新时间：2020-08-12
- 摘要：Novel blue-emitting material, Eu2+-doped Ca3SiO4Br2 was reported in this paper. Flaky crystals of Ca3SiO4Br2 were grown out of high-temperature Ca2SiO4/CaBr2 melts. The crystal structure was determined as the chemical composition of Ca3SiO4Br2, and structural investigations have also shown that Ca3SiO4Br2 is composed of the layers of calcium chloride and dicalcium silicate. Based on the photoluminescence analysis, Ca3SiO4Br2∶ Eu2+ phosphor exhibited a broad blue emission band of main peak at 470 nm under the near ultraviolet (n-UV) light (300~450 nm), and efficient n-UV absorption property can be testified by UV-Vis diffuse reflectance spectra. It indicated that halosilicate materials Ca3SiO4Br2∶ Eu2+ phosphor is an excellent phosphor in the application of the white LEDs.关键词：white light LED lighting;blue emission phosphor;halosilicate;crystal structure;rare earth luminescence128|93|3更新时间：2020-08-12
- 摘要：Water soluble NaYF4∶20%Yb3+,3%Er3+ (mole fraction) upconversion nanoparticles (UCNPs) were synthesized by facile solvothermal method using polyvinylpyrrolidone (PVP) as the surfactant. The size and morphology of the UCNPs were confirmed by scanning electron microscopy (SEM). The SEM images showed almost all the UCNPs were nanospheres and the size was about 40 nm. Under the 980 nm excitation, the UCNPs exhibit bright yellow light. The UCNPs could be well dispersed in water to form a clearly transparent solution. MTT assay was performed to analyze the biotoxicity of the UCNPs. The results showed the NaYF4∶Yb3+/Er3+ UCNPs modified by PVP had fairly biological compatibility and no biotoxicity for HeLa cell line, even the concentration of UCNPs reached 200 mg/mL. These results showed that the UCNPs had potential applications in biological field as luminescence labeling probes.关键词：water soluble nanopartical;rare earth;upconversion luminescence;biological compatibility131|54|0更新时间：2020-08-12
- 摘要：Polyaniline (emeraldine base, EB) powder was dissolved in n-methylpyrrolidone (NMP). Then the NMP solution of EB was cast on glass substrate and dried under a vacuum to obtain the EB film. The EB film was doped by exposing them in the atmosphere of hydrogen chloride volatilized by hydrochloric acid. The doped degree was controlled by the concentration of hydrochloric acid solution and different time that the film was exposed in HCl gas. The results show that, in the beginning, the infrared reflectivity of the film in the atmospheric window increases with the doped degree increases. Then the infrared reflectivity begins to decrease after the doped degree come to a certain degree. At last, the value of infrared reflectivity keep steady. The highest reflectivity in the wave range of 3~5 μm is 53.1%, and the highest reflectivity in the wave range of 8~14 μm is 57.6%. The doped degree when the highest reflectivity appears in different wave range is diffe-rent. The interference comes from the thickness of the film also influences the reflectivity in some narrow wave range. Due to the simpleness of the doped method, it is easy to realize the camouflage with thermal colors. The microwave absorption property of the EB film with different doped degree was also investigated. In general, all EB films with different doped degree show the excellent transmittance. In some wave range, the EB film with proper doped degree can also absorb the microwave. It can be used as a part of stealthy composite material to cover the targets on the ground.关键词：polyaniline;infrared stealthy;microwave absorption;doping113|222|2更新时间：2020-08-12
- 摘要：ZnO∶Eu3+ thin films were deposited on quartz substrates by radio frequency(RF) magnetron sputtering. The lattice structure, surface morphology and photoluminescence (PL) properties were analyzed by X-ray diffractometer (XRD),scanning electron microscope (SEM) and spectrometer, respectively. Effects of RF sputtering power and heat treatment on the structure and PL properties were studied in detail. The results showed that all the ZnO films had a hexagonal wurtzite structure and a higher RF sputtering power was beneficial to (002) preferred orientation. The films grains grew up as the RF sputtering power and heat treatment temperature increased. Moreover, we observed the phenomenon of electron transitions in intra-4f shell of Eu3+ and energy transfer from ZnO host to the doped Eu3+ in these ZnO∶Eu3+ films. Besides, as the RF sputtering power increased and after annealed at 780 ℃, the PL properties of ZnO∶Eu3+ films were obviously improved.关键词：ZnO∶Eu3+;photoluminescence;magnetron sputtering121|192|2更新时间：2020-08-12
- 摘要：The salmon pink phosphor CaZn2(PO4)2∶Eu3+ was synthesized by high temperature solid state reaction, and its luminescent characteristics were also investigated. The excitation spectra contains a broad band extending from 350 to 420 nm, which is suitable for UVLED chip, and its main peak located at 394 nm. It showed that the emission spectra of the phosphor was composed of four group major emission peaks locating at 585 and 595 nm, 615 and 622 nm, 654 nm, 687 and 700 nm which corresponding to the 5D0→7F1,5D0→7F2,5D0→7F3 ,5D0→7F4 typical transition of Eu3+, respectively. The effects of doped-Eu3+ concentration to the emission intensity and the ratio of IO/IR were also investigated. It showed that the optimum doped-Eu3+ mole fraction is 10%. The charge compensation of Li+, Na+ and K+ ions to the emission intensity was also studied, and it found that Li+ ions gave the best improvement to enhance the intensity of the emission.关键词：luminescence;phosphor;CaZn2(PO4)2∶Eu3+97|88|4更新时间：2020-08-12
- 摘要：GaN films with SiNx interlayer were grown on sapphire substrates by metal organic chemical vapor deposition. The effect of nanoporous SiNx interlayer growth position on the properties of high-quality GaN epitaxial films was investigated systematically. The high-resolution X-ray diffraction spectra was achieved when a SiNx interlayer was adopted and inserted on a rough GaN layer. The screw and edge dislocation densities have been calculated. The optical and electrical properties of the GaN films were characterized by Raman scattering spectra, low temperature photoluminescence spectra and Hall measurements, etc. The position of the SiNx interlayer has no impact on the strain in GaN films,but the residual carrier concentration changes with the position of the interlayer.关键词：metalorganic chemical vapor deposition;GaN;SiNx;high resolution X-ray diffractions132|68|2更新时间：2020-08-12
- 摘要：By introducing the GaAs interlayer and controling growth temperature, the p-type ZnMgO films were grown on (0001) Al2O3 substrates by metal organic chemical vapor deposition (MOCVD) method. The X-ray diffraction results indicated that the ZnMgO films showed c-axis preferential orientation at temperature of 440~520 ℃. A conversion of conduction type was confirmed by Hall effect measurement in a range of temperature from 480 to 520 ℃. The lowest resistivity was 26.33 Ω·cm, with a carrier concentration of 1.638×1017 cm-3, and a hall mobility of 1.45 cm2/(V·s). The room temperature photoluminescence (PL) spectrum displayed all the p-type ZnMgO films showed good optical qualities, with a big ratio of near band emission (NBE) to deep level emission (DLE).关键词：ZnMgO films;p-type doping;MOCVD139|124|0更新时间：2020-08-12
- 摘要：4,4'-(quinoxaline-2,3-diyl)bis(N,N-dimethylaniline) (QBDMA) was synthesized and its structure was fully characterized by UV-Vis absorption spectra, IR spectra and 1H NMR spectra. The electrochemical analysis was also performed to determine the energy of the frontier molecular orbitals of QBDMA. It was found that QBDMA can be used as the pH sensor of the proton donor compounds based on the analysis of its photophysical properties. At last, the ground state geometry structure of QBDMA was optimized, and the UV-Vis absorption spectra of QBDMA were simulated in DMF and EtOH media at B3LYP1/6-31G* level.关键词：photophysics;theoretical calculation;quinoxaline;luminescent sensor112|232|2更新时间：2020-08-12
- 摘要：A new Ce3+/Tb3+ co-doped BaYF5 glass ceramic was prepared by high temperature melting. The X-ray diffraction spectra, excitation spectra and emission spectra were measured. The results indicate the BaYF5 nanocrystalline phase exists in the glass matrix. Based on the Scherrer equation, the average size about 27 nm of BaYF5 nanocrystalline was calculated. The intense blue emission band(425 nm)assigned to 5d→2F5/2 and 5d→2F7/2 transitions of Ce3+ and blue emission(487 nm), green emission (542 nm), orange emission (582 nm) and red emission (620 nm) assigned to 5D4→7FJ(J=6,5,4,3) transitions of Tb3+ ions, respectively, were observed at room temperature under 338 nm excitation in the glass ceramics. By adjusting the doped concentration of Ce3+ and Tb3+, the chromaticity coordinate of the glass ceramic is measured to be (0.287, 0.336). The energy transfer between Ce3+ and Tb3+ was analysised systematically. The results indicate that Ce3+ / Tb3+ co-doped BaYF5 glass ceramics is a potential matrix material for white LED.关键词：Ce3+/Tb3+ co-doped;glass ceramics;energy transfer;white light LED128|741|2更新时间：2020-08-12
- 摘要：As the increasing applications of laser diodes in laser cladding and laser hardening, the single laser diode optical power can not meet the actual requirements. An improvement of the power and power density is necesary and it can be achieved by beam shaping and beam combination such as polarization coupling. The polarization coupling technology is used to couple two laser beams with thin-film plate polarizer. In this paper, two 808 nm vertically stacked arrays with an output power of 1 500 W was achieved. After fast axis and slow axis collimated, the polarization direction of one stacked arrays is rotated 90° through a half wave plate, thus, the polarization directions of two laser stack are vertical. The beams of two lasers are incident on thin-film plate polarizer; one transmits through it, and the other is reflected on it. Finally, two beams combine to one. Polarization coupling of two bars increases the power by a factor of 1.6, and the output power is 2 600 W, electro-optical conversion efficiency is more than 48%. The spot size is about 1 mm ×2 mm. This source reaches an intensity of 130 kW·cm-2. This laser can be directly applied to cladding, surface hardening and other fields.关键词：laser diode;high efficiency;polarization coupling;thin-film plate polarizer126|121|4更新时间：2020-08-12
- 摘要：High performance organic light emitting devices (OLEDs) should have a low operating voltage, high efficiency and relatively good stability. Inserting of a hole blocking layer (HBL) between hole transporting layer (HTL) and electron transporting layer (ETL) is one of the effective method to improve device performances. In this paper, a DPVBi HBL was incorporated in OLED between the PEDOT∶PSS hole injection layer (HIL) and Alq3 ETL. Such a structure helps to reduce the hole-leakage of the cathode, which resulting an enhanced device performances. The optimized device with a thickness of 30 nm DPVBi HBL shows a signi-ficantly improved current efficiency (5.2 cd/A) and luminance (24 350 cd/m2), which is 20% and 87% higher compared with those data of reference device with the structure of ITO/PEDOT∶PSS/NPB/Alq3/LiF/Al.关键词：OLED;hole blocking layer;DPVBi151|186|1更新时间：2020-08-12
- 摘要：Accelerated aging test at the temperature of 85 ℃ were carried out on high-power GaN-based white light-emitting diodes. The degradation of main performance parameters was investigated. After 6 500 h, the luminous flux rate of the samples was declined about 28% to 33%. Series resistance and reverse leakage current increased with the aging time, which were caused by the degradation of ohmic contact and the increase of the defect density, respectively. The thermal resistance components of LEDs increased gradually. Based on the C-SAM measurement, some voids appeared in the die attach. The experiment results suggested that the degradation both in chip and packaging lead to the invalidation devices.关键词：high-power white LED;aging test;thermal resistance;failure analysis137|229|8更新时间：2020-08-12
- 摘要：An array of 320×240 micro-LED is designed based on AlGaInP epitaxial wafer. The pixel size is 100 μm×100 μm.The optical properties of LED array are affected by the current crowding effect, which is a universal problem in LED array. By simulating the active layer current distribution, effects of some factors including electrode structure,width of electrode and distance between electrodes on the current distribution of LED array are studied. The tri-strip electrode is proposed as an optimized structure of the top electrode. Considering some important details such as the light shading effect, the tri-strip electrode is the best electrode shape comparing with one-strip electrode and bi-strip electrode. The optimized electrode leads to the more uniform current spreading.The uniform lighting area of active layer increase 65.02% and 25.63% than that one strip electrode and bi-strip electrode, respectively. The light emission efficiency of the micro-LED array can be improved.关键词：electrode structure;AlGaInP-LED;current distribution;tri-strip electrode127|149|0更新时间：2020-08-12
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Influence of Optical/Electrical Excitating Style on The Deality Factor of AlGaInP and GaN-based LEDs
摘要：The electrical characteristic of AlGaInP and InGaN/GaN-based LEDs were measured and explored under optical and electrical excitation. One of the significant parameter of LED characteristic, n, was mainly taken into consideration under the two varied excitation styles. The results showed that both junction temperature and injecting intensity of carrier influenced n. The essential performance of devices was gained within injecting intensity range where the action of space-charge region plays the most important role on current transferring. We found n, obtained in different motivation conditions, is independent on the excitation ways. Therefore, optical excitation can be applied to take place of electrical excitation for the non-contact detection of n in LEDs.关键词：ideality factor;light-emitting diode;optical excitation;electrical excitation;junction temperature135|111|0更新时间：2020-08-12 - 摘要：High-power high-brightness tapered laser diodes emitting at 850 nm have been manufactured, and the beam quality of near diffraction limit has been achieved. The beam propagation factor M2 is only 1.7 and the high brightness is up to 16.3 MW·cm-2·sr-1 when the output power is 200 mW, and the values change to 2.8 and 9.9 MW·cm-2·sr-1 under 1 W output. The electro-optical properties of tapered lasers are discussed. We have also studied the influence of tapered section length on output power. The results reported in this paper may become a step forward to new applications of tapered laser diodes.关键词：850 nm;tapered laser diode;high brightness;the beam propagation factor M2177|2139|1更新时间：2020-08-12
- 摘要：The relationship between the thickness d of p-type GaN and light extraction efficiency of GaN based vertical light emitting diodes (VLEDs) was described in this work. The VLEDs were grown on silicon by metal organic chemical vapour deposition (MOCVD). A series of VLEDs were fabricated with varied thickness of p-type GaN. It showed that the thickness d was in the order of wavelength and it had a significant influence on extraction efficiency due to interferences. The maximum in extraction efficiency was two times more than the neighboring minimum, which were located at 0.73λn and 1.01λn, respectively. Therefore, the extraction efficiency of VLEDs can be enhanced by optimizing the thickness of p-type GaN.关键词：LED;GaN;vertical structure;light extraction;thickness of p-type GaN142|179|0更新时间：2020-08-12
- 摘要：The mixed-lamps of bromine tungsten lamps and LEDs were proposed to serve as integrating sphere inner source and LEDs were driven by constant current. Simulated Annealing (SA) algorithm was introduced to study the spectral matching technique of spectrum-tunable integrating sphere light source (STIS). The simulation experiment indicated that mixed-lamps could not only mimic CIE-D65 and equi-energy spectra successfully, but also improve the performance of STIS. The numbers of LEDs reducing 79.8% and 82.9%, respectively, and the average relative error reducing 10% and 40.5%, comparied with LEDs simulation results. A feasible mixed-lamps scheme for Ф 0.5 m integrating sphere, whose maximal radiance between 380 nm and 900 nm is no less than 50 W/(m2·sr). The validating experiment indicated that the SA algorithm and constant current drive mode would be feasible in STIS' engineering practice.关键词：LED;bromine tungsten lamp;integrating sphere light source;spectrum-tunable;spectral matching133|202|12更新时间：2020-08-12
- 摘要：A DOSC-WPT-PLS method based on partial least squares (PLS) regression with direct orthogonal signal correction (DOSC) and wavelet packet transform (WPT) as preprocessed tools was proposed for the simultaneous fluorespectrophotometric determination of Vitamin B1, vitamin B2 and vitamin B6. A program (PDOSCWPTPLS) was designed to execute the relative calculations. Three chemometric methods (DOSC-WPT-PLS, WPT-PLS and PLS) were compared in this study. The relative standard errors of prediction (RSEP) obtained for all components with DOSC-WPT-PLS, WPT-PLS and PLS were 2.29%, 4.23% and 5.36%, respectively. Experimental results showed that the DOSC-WPT-PLS method was successful and had advantages over the WPT-PLS and PLS. The method was applied to determine the contents of vitamin B1, vitamin B2 and vitamin B6 in the tap water with satisfactory results and their recoveries were 93.4%~109.2%, 91.0%~105.2% and 94.7%~107.7%, respectively.关键词：chemometric;fluorespectrophotometry;simultaneous determination;vitamin B124|139|1更新时间：2020-08-12
- 摘要：Making use of optical tweezers Raman spectroscopy system to study the differences between normal human red blood cells and the red blood cell RBC in patients with myocardial infarction. We also investigate the changes of the contents in RBC and its variation mechanism. It is hopeful to provide a new, quick and easy method to diagnosis this disease, and may provide reliable experimental evidence for clinical diagnosis.关键词：myocardial infarction;optical tweezers;raman spectra;red blood cells118|161|0更新时间：2020-08-12
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