最新刊期
卷 32 ， 期 8 ， 2011
- 摘要：Metal-oxide-semiconductor structure of ITO/Si-rich SiO2∶Er/Si containing erbium ions and silicon nanocrystals was fabricated by ion implantation of Si and Er combined with post-annealing. The electroluminescence spectra and current-voltage characteristics were measured to investigate the influence of silicon concentration on the excitation mechanism of luminescence centers and conductance process. It was found that the excitation mechanism of erbium ions was variational in the MOS-LED with silicon content. For the silicon concentration less than 5%, the upper levels of erbium can be excited by resonant energy transfer from silicon-oxygen deficiency centers, which induce an enhancement of the 522 nm peak emission intensity of Er3+ ion. For the silicon concentration above 5%, the excess silicon formed silicon nanocrystals by post-annealing. The direct tunneling of electrons between silicon nanocrystals dominate the conductance, resulting a decrease of average energy of hot electrons and quenching of all the electroluminescence peaks of erbium.关键词：erbium-doped silicon nanocrystal;electroluminescence;ion implantation;MOS-LED104|50|1更新时间：2020-08-12
- 摘要：Sr1-xBaxAl2O4∶Eu2+ phosphors were synthesized in a reducing atmosphere by high temperature solid state method at 1 350 ℃. The patterns of XRD indicated that the crystal structure of the phosphors are the monoclinic phase of SrAl2O4 when x<0.4 and the simple hexagonal phase of BaAl2O4 when x≥0.4 because of crystal lattice expands with Ba2+ ion substitution for Sr2+ ion. Photoluminescence experiments were carried out to study the luminescence properties of the phosphors excited under 360 nm. The results showed that emission spectra gradually changed from single green emission (λmax=516 nm) to blue-green dual-emission (λmax1= 441 nm, λmax2=486 nm) with the increase of x. When x was 0.5, there was a better property in Sr0.5Ba0.5Al2O4∶Eu2+. From the relationship between the concentration of Eu2+ ion and the intensities of emissions in Sr0.5Ba0.5Al2O4∶y%Eu2+, we get that the maximum dual-emission intensity when y=0.29%. There exist a concentration quenching effect in Sr0.5Ba0.5Al2O4∶Eu2+, and the study points out that the mechanism of concentration quenching effect is electric dipole-dipole interaction.关键词：white LED;phosphors;SrAl2O4;concentration quenching127|41|0更新时间：2020-08-12
- 摘要：Optically transparent Er3+/Yb3+ codoped glass ceramics based on the system 60TeO2-10CaF2-25H3BO3-1Er2O3-4Yb2O3 have been successfully prepared by melt-quenching method at 900 ℃.The Er2Te5O13 nanocrystals, whose phonon energy was 886 cm-1 by Raman measurement, were characterized by XRD and TEM in the tellurite glass ceramics. Both up-conversion and down-conversion emission spectra were measured. The red and green emissions have different luminescent processes under different excitation sources. The energy transfer processes were discussed individually.关键词：Er3+/Yb3+;glass ceramics;energy transfer90|38|2更新时间：2020-08-12
- 摘要：The long afterglow luminescence materials of SrAl2O4∶Eu2+ ,Dy3+ was synthesized by a two-step spray pyrolysis process. Structure, morphology and luminous performances of SrAl2O4∶Eu2+ ,Dy3+ were investigated via the technologies of X-ray diffraction, field emission scanning electron microscopy, emission spectra and so on. The results showed that the higher pyrolysis temperature was conductive to formation of SrAl2O4∶Eu2+ ,Dy3+ spherical particle. The initial brightness, afterglow time, emission peak intensity of SrAl2O4∶Eu2+ , Dy3+ increased with temperature and reached the maximum at 850 ℃.The emission spectrum shape of SrAl2O4∶Eu2+ ,Dy3+ that prepared by different pyrolysis temperatures are similar, with wideband peaked at about 512 nm, corresponding to the emission caused by the typical Eu2+ 5d → 4f (4f65d configuration to the ground state 4f7) transition, it is just difference in relative strength and the peak emission spectrum does not change. The afterglow time was prolonged by adding appropriate amount polyethylene glycol, and it was the longest when the dosage was 0.03 mol/L. Adding citric acid reduced the afterglow time of luminescent materials, and the afterglow performance declined slowly when the content changes from 0.1 g/L to 0.3 g/L. Additivesis was beneficial to formation of luminescent global particles. The liquid drop of disperse and spray showed a better effect when the polymeras can be synthesized by the esterification of polyethylene glycol and citric acid at high temperature. With increasing the reduction temperature, the afterglow properties of SrAl2O4∶Eu2+ ,Dy3+ prepared via spray pyrolysis method increased firstly and then decreased. The best reduction temperature was 1 250 ℃ which was distinct advantage over by solid state method. The SrAl2O4∶Eu2+ ,Dy3+ prepared by spray pyrolysis belongs to the ɑ-SrAl2O4 phosphor crystal structure and it do not affect the crystal structure of SrAl2O4 when a small amount of Eu and Dy introduced into the mixture. The emission spectrum shape of SrAl2O4∶Eu2+, Dy3+ of obtained by two methods are similar, both wideband spectrum and the peaks corresponding to the typical 4f→5d transition of Eu2+ were observed at 512,513,516,518 nm,respectively. With the rising of reduction temperature, the emission in the main peak all showed an obvious red shift.The results showed that the synthesis temperature used spray pyrolysis method can be significantly reduced, and the sample received more regular morphology, smaller particle size, narrower particle size distribution and more excellent luminescent properties, comparing with that prepared by solid state method.关键词：spray pyrolysis process;SrAl2O4∶Eu2+;Dy3+;long afterglow;luminescent performances175|168|0更新时间：2020-08-12
- 摘要：According to Monte-Carlo ray tracing method, this paper simulated the GaN-based flip-chip LED light extraction efficiency (LEE), compared the differences between the status of sapphire with substrate and without it, with one side roughening and double sides roughening, with and without buffer layer, and made further selection and optimization about the structure and the size of surface roughing unit. The results showed that both the thicker substrate and introduction of AlN buffer layer were favorable for the increase of LEE, the LEE for the chip with double surfaces roughened sapphire substrate was significantly better than the one with single surface roughened sapphire substrate, the structure and size of the surface roughing unit have great influences on the LEE, the LEE was relatively higher when the size of micro roughened structure was comparable to its one-to-one distance.108|61|4更新时间：2020-08-12
- 摘要：Trivalent terbium (Tb3+) doped strontium molybdate (SrMoO4) was synthesized by sol-combustion method and the crystal structure and luminescent properties were investigated in this paper. The X-ray diffraction patterns (XRD) showed that the phosphors sintered at 750 ℃ for 3 h were pure SrMoO4 phase. The excitation spectrum consisted of a broad band and a series of narrow bands, in which the higher energy peaks located at 288 nm and 375 nm, respectively. The emission spectrum was composed of four narrow bands and the strongest emission peak was located at 548 nm. The appropriate doping molar fraction of Tb3+ was 0.05 for the 548 nm emission. The concentration quenching of 548 nm (5D4→7F5) was attributed to d-d interaction. When the dosage of urea was 3 times of theory dosage, the luminescent intensity reached the maximum. The optimal sintering temperature and time were 750 ℃ and 3 h, respectively. These results showed that this Tb3+ activated SrMoO4 was a promising green phosphor for ultraviolet (UV) and blue InGaN-based white LED.关键词：Tb3+;SrMoO4;sol-combustion method;green phosphor97|45|9更新时间：2020-08-12
- 摘要：Silica xerogels doped with Eu3+ ions and co-doped with Eu3+ /CdS nanoparticles were prepared through a two-step hydrolysis process. The effect of annealing temperature on photoluminescence properties of Eu3+-doped silica xerogel was investigated. The results showed that the photoluminescence intensity of Eu3+-doped silica xerogels was significantly dependent on the annealing temperature, which was closely related to the amount of the defect in xerogel network. The emission intensity increased with the annealing temperature from 40 ℃ to 300 ℃ . But when the temperature exceeded 300 ℃, the intensity decreased with the annealing temperature. The study of the photoluminescence of co-doped xerogels showed that the intrinsic emissions due to 5D0→7FJ transitions of Eu3+ were observed, and the intensity was sensitive to the surface states of CdS particles and of the porous silica gel.关键词：photoluminescence;CdS nanoparticles;Eu3+;co-doped;silica xerogel95|39|0更新时间：2020-08-12
- 摘要：Self-assembled GeSi quantum dots (QDs) were grown by gas source molecular beam epitaxy (MBE). Morphology and optical properties of the QDs were studied by atomic force microscopy (AFM) and photoluminescence (PL) spectra. QDs structure grown by gas source MBE at lower temperature showed a higher QDs coverage, lower defect and impurity density. Below 200 K, carriers are trapped in QDs as excitons with bonding energy of about 17 meV.The transport process changes as increasing the temperature to 200 K. By fitting the temperature dependence curves of PL integrated intensity, the activation energy of 129 meV representing the energy difference between the wetting layer and QDs was obtained.关键词：gas source MBE;GeSi quantum dots;exciton;PL;thermal quenching93|55|0更新时间：2020-08-12
- 摘要：CdS thin film was prepared by chemical bath deposition at different n(S) ∶n(Cd) using the precursors of CdCl2·H2O, CS(NH2)2,NH4Cl,NH3·H2O and deionized water. The surface morphology, structure and optical properties of all the samples have been analyzed by scanning electron microscopy, X-ray diffraction,transmission and photoluminescence (PL) spectra. The results indicated that spherical particle like morphology and cubic structure CdS thin films were obtained at n(S) ∶n(Cd) greater than or equal 3 ∶1.All CdS thin films with a close stoichiomerty S/Cd=0.91 were Cd-rich belong to n-type semiconductor.The absorption edge of CdS films was about 450 nm, the optical transmittance was more than 70% in the wavelength range from 510 to 2 500 nm.Intensity of the photoluminescence peak at 500 nm is stronger.关键词：chemical bath deposition;CdS thin film;n(S)∶n(Cd);photoluminescence96|34|0更新时间：2020-08-12
- 摘要：Fluorescent hybrid nanospheres of SiO2/Rhodamine B were prepared. Firstly, 3-glycidyloxypropyl trimethoxysilane (KH560) reacted with Rhodamine B in water-in-oil microemulsion, and then they reacted with TEOS in the microemulsion by sol-gel in-situ. The hybrid nanospheres were characterized by FTIR,UV-Vis, TG, PL and TEM. The results showed that Rhodamine B was linked to SiO2 via chemical bond,the diameter of hybrid nanospheres was about 200 nm. The nanospheres showed better heat resistance and UV light resistance than Rhodamine B. The PL intensity of the hybrid nanospheres was about 4 times of Rhodamine B.关键词：SiO2;rhodamine B;nanospheres;organic-inorganic hybrid;microemulsion135|48|1更新时间：2020-08-12
- 摘要：Strontium fluoride (SrF2) was used as the p-type dopant in hole transporting layer (HTL) of blue phosphorescent OLEDs with different doping ratios. The hole injection and transporting of devices have been significantly improved. The 6% doping ratio device showed a high power efficiency (19.1 lm/W), current efficiency (26.9 cd/A), and luminance (22 220 cd/m2), which was superior to those for traditional ITO anode reference device with the data of 10.3 lm/W, 18.6 cd/A, and 12 320 cd/m2, respectively.关键词：blue phosphorescent OLED;hole transporting layer;doping;SrF2105|38|2更新时间：2020-08-12
- 摘要：The light out-coupling efficiency of polymer light-emitting devices (PLED) flat panel based on poly (MEH-PPV) was simulated by applying the transfer matrix method and software MATLAB. The influence of emitting layer, PEDOT layer, ITO layer on the performance of the PLED flat panel’s out-coupling efficiency was studied. The influence of different micro shapes on glass surface, such as flat panel, hemispherical shape,circular mesa,and conical shape, is simulated by software TRACEPRO. The results show that the light out-coupling efficiency is the largest and the uniformity of flat panel light output is the best when the glass surface is with micro conical shape. At last, the thermal properties were studied during the working of PLED flat panel. A great quantity of heat in emitting layer can not be diffused quickly. These results provided a basis for the optical and thermal optimization of PLED flat panel light source.关键词：polymer light-emitting diode flat panel lighting source;out-coupling efficiency;light output uniformity;thermal characteristics109|49|0更新时间：2020-08-12
- 摘要：In the third-generation low-level-light image tube, a super thinner ion barrier film (IBF) was covered on the input surface of microchannel plate (MCP) to protect the photocathode and prolong the operation life of the image tube. In order to further investigate the properties of IBF, a Monte-Carlo simulation on the stopping and transmission characteristics of particles in Al2O3 and SiO2 IBFs were conducted. It was found that the dead-voltage was 230~240 V and 220~230 V for Al2O3 and SiO2 IBF with the thickness of 5 nm, respectively. The number of the back-scattered electron was as high as 19% for the incident electrons with energy of 0.24 keV. For the incident energy of 0.8 keV, the electron transmittance was 87.16% and 88.12%, and the limited thickness of the IBF was 15 nm and 16nm for Al2O3 and SiO2 film, respectively. For C+, N+ and O+ ions with energy of 0.26 keV, the ion stopping power was 95%~99% for Al2O3 IBF. The Al2O3 IBF showed satisfied electron transmittance and ion stopping power when the thickness of IBF was 5 nm.关键词：microchannel plate;ion barrier film;Monte-Carlo simulation;electron transmittance;ion stopping83|53|0更新时间：2020-08-12
- 摘要：The ZnMgO/n-ZnO/ZnMgO/p-GaN heterojunction LED was fabricated by plasmas assistant molecular beam epitaxy (P-MBE) on GaN substrate. Ni/Au contact to the p-GaN layer and In contact to the n-ZnMgO showed a good ohmic contact behavior. This heterojunction showed a good diode rectifying behaviors with turn-on voltage of 2~3 eV. The EL spectra consist of a strong peak at 370 nm and a weaker broad band centered at 430 nm under the forward current at 20 mA. It concluded the 370 nm emission belong to ZnO free exciton recombination, and the 430 nm emission to the defect of GaN substrates by comparing with the PL spectra of ZnO and GaN. By observing the ZnO free exciton emission in ZnMgO/n-ZnO/ ZnMgO/p-GaN, the heterojunctions could be attributed to the double heterojunction structures. The double heterojunctions could block the electrons of ZnO from passing across the ZnMgO layer and entering into the GaN layer. As for holes, the barrier height that hinders the holes in p-GaN from entering into the ZnO is much smaller.关键词：ZnO;GaN;ZnMgO;electroluminescence113|66|2更新时间：2020-08-12
- 摘要：W∶Bi4Ge3O12 and Bi12GeO20 crystals were prepared by Czochralski(Cz) method. The absorption, photoluminescence (PL) and PL lifetime spectra were investigated. The results revealed the PL intensity of W∶Bi4Ge3O12 was stronger than that of Bi12GeO20, and annealing in N2 can increase the PL intensity of W∶Bi4Ge3O12. Near infrared PL (at about 745 nm) was observed in Bi12GeO20 annealed in N2, and the lifetime was about 10 μs. The mechanisms of luminescence in W∶Bi4Ge3O12 and annealed Bi12GeO20 was discussed.关键词：W∶Bi4Ge3O12;Bi12GeO20;photoluminescence;anneal127|53|0更新时间：2020-08-12
- 摘要：A CW, LD pumped Nd∶YVO4, 532 nm green laser with high stability output power of 144 mW was reported. The laser stability was achieved by double closed-loop feedback system, which provided the high accuracy temperature control of LD and KTP crystal by thermoelectric cooler (TEC) and feedback control of laser power. The accuracy of temperature control reached the level of ±0.1 ℃ in the experiment. Meanwhile, the real-time feedback of LD output power was based on the error variance of nonlinearity curve by Si-photo detecting variables with LD current. Threshold mode PI control algorithm could reduce the stable error and their output signals were used to adjust LD pump current source as so to gain the output power stability. The long-term stability was excellent with ±1% variation in the output power.关键词：laser diode (LD);high stability laser;temperature control;optic feedback115|71|3更新时间：2020-08-12
- 摘要：The devices of top-emitting 4×4 VCSELs array with the emission wavelength of 850 nm was produced, and the production process of VCSELs were described. Coherence of the device were measured, the visibility of interference figure was calculated, and the effect factor of interference fringe visibility was also analyzed.关键词：vertical-cavity surface-emitting laser;array;coherence102|74|0更新时间：2020-08-12
- 摘要：On the basis of a traditional phosphorescent organic light emitting device (PHOLED) with the structure of ITO/NPB/CBP∶Ir(ppy)3/BAlq/Alq3/LiF/Al, a new structure PHOLED was fabricated in this paper, where concavo-convex shape was constructed at the NPB/CBP∶Ir(ppy)3, CBP∶Ir(ppy)3/BAlq and BAlq/Alq3 interface. A series of measurements of optical and electrical properties of device indicated that, (1) this concavo-convex interface structure with suitable protrusion thickness can reduce current density of device, hence reduce the formation of phosphorescence quench centers induced by high current density, (2) it can increase the area of charge carrier recombination interface and then disperse triplet excitons, hence decrease triplet-triplet quenching, (3) it can enhance the out-coupling of the waveguide light without spectral distortion. Therefore, this new structure with suitable protrusion thickness can increase remarkably the current efficiency of the device. When the protrusion thickness was 10 nm, the maximum current efficiency of the device can reach to 34.0 cd/A with an increase of 55% compared with the traditional device.关键词：organic light emitting devices;phosphorescence;interface;luminous efficiency110|63|1更新时间：2020-08-12
- 摘要：ZnO nanowires were assembled on Au interdigital electrodes by dielectrophoresis method and fabricated the nanowires UV detector. In order to assemble the ZnO nanowires on interdigital electrodes, the long ZnO nanowires were grown three times by hydrothermal method. Then, the ZnO nanowires was annealed under 700 ℃, which increased the availability of the surface defects. The photoresponse current ratio and recovery time of the UV detector fabricated with the annealed ZnO nanowires were significantly improved. The possible mechanism was studied by the photoluminescence and photoresponse spectra.关键词：ZnO nanowire;dielectrophoresis;nanodevice;UV detector96|58|1更新时间：2020-08-12
- 摘要：Mesoporous hexagonal silica MCM-41 with pore sizes of 2.7 nm was synthesized and was used as host materials for the fabrication of photodynamic therapy materials by loading of rose bengal. Nitrogen sorption techniques, transmission electron microscopy, scanning electron microscopy, and X-ray diffraction were used to characterize the particles. The UV-Vis and photoluminescence of rose bengal in the channels of MCM-41 were also investigated. The functionalized composites showed strong fluorescence and obvious redshift of emission band comparing with rose bengal in DMF.关键词：mesoporouse materials;photosensitizing agent;photodynamic therapy139|62|0更新时间：2020-08-12
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