最新刊期
卷 37 ， 期 11 ， 2016
- 摘要：High quality GaN-based material system is the basis of developing the third generation semiconductor optoelectronic and microelectronic devices. The GaN-based materials and quantum structures have the properties of large mismatch, strong polarization, and nonequilibrium growth. The research on growth dynamics and carrier control of GaN-based material has important research significance and practical value, and is attracting the attention of scientific and industrial communities. In this paper, the growth dynamics and carrier control of GaN-based material with large mismatch and strong polarization is investigated, in order to get over the bottle-neck of low emitting efficiency of blue light, break through the difficulty of fabricating GaN-based material with high Al- and high In-composition, and achieve high mobility of heterostructure material and high quantum efficiency of optoelectronic devices. By the fabrication of emitting devices with high-efficiency multi-wavelength and electronic devices with high-frequency high-breakdown, the technology innovation, industrial transformation and upgrade can be realized.关键词：GaN;large mismatch;strong polarization;growth dynamics;carrier control139|205|1更新时间：2020-08-12
- 摘要：Facing on the problem that the existing photocatalysts' sunlight response performance is poor, and the fact that the existing photocatalysts with visible light photoresponse are poorly functioned and tough to prepare, the upconversion luminescence materials with the exact matrix of TiO2 are prepared, and the photoluminescence capacity of materials doped with different ratio of n(Yb3+): n(Tm3+) is studied. Firstly, the materials doped with the designed range of n(Yb3+): n(Tm3+) ratio were prepared by the sol-gel method. Secondly, the performance of prepared photocatalysts was examined by UV-Vis, 3D-EEM and experiments of photocatalytic degradation. Lastly, based on the analysis of the data, an optimum ratio of n(Yb3+): n(Tm3+) was determined. The results show that the materials with n(Yb3+): n(Tm3+) ratio of 4 give the most obvious upconversion luminescence phenomenon and the best degradation effectiveness, with the target organic pollutant removed by 33.33% within 4 h, 49.99% degraded within 6 h and 72.87% degraded within 12 h. It is proved that allowing TiO2 to function as a photocatalyst as well as to assist in the photoluminescence procedure at the same time saves both complicated preparation procedures and over-wasted energy. In addition, the ideal photocatalyst TiO2: 1%Tm, 4%Yb achieves ultraviolet upconversion under visible light and thereby enhances the photocatalyst's sunlight response ability.关键词：TiO2;photocatalysis;visible light;upconversion;n(Yb3+): n(Tm3+)133|61|4更新时间：2020-08-12
- 摘要：Pure and Mg2+-Ni2+ doped LaFeO3 were prepared by sol-gel method, and their emission rates in the near infrared band were studied and compared. The results show that the infrared emission rate in 0.2-2 μm waveband of LaMg0.34Ni0.23Fe0.43O3 (Mg2+ mole fraction of 34%, Ni2+ mole fraction of 23%) is 0.966, much higher than that of undoped LaFeO3(0.446). For Mg2+-Ni2+ co-doped LaFeO3, Mg2+, Ni2+ come into lanthanum ferrite lattice to substitute Fe3+, which introduces the impurity levels and increases the oxygen vacancy concentration. The impurity energy absorption and absorption of oxygen vacancies are improved, and the lattice distortion induced by doping makes the lattice vibration absorption enhance. In addition, the polarized transition of electrons between Fe3+ and Fe4+ greatly enhances the absorption performance of the compounds in the corresponding spectra. So, Mg2+-Ni2+ co-doping can significantly improve the infrared emission rate of LaFeO3.关键词：perovskite;lanthanum ferrite;doping;absorptivity;infrared emissivity123|50|0更新时间：2020-08-12
- 摘要：As an superior performance of laser crystal, Yb-doped YAG crystal has been widely used in high efficiency and power laser field. New research has shown that the response time of Yb: YAG can attain up to 0.411 ns. The super ultrafast scintillation property of Yb: YAG ultrafast scintillator has attracted broad attention in many researches such as pulsed radiation detection, inertial confinement fusion, space radiation detection and nuclear reaction kinetics. First of all, we described the research progress and ultrafast scintillation mechanism of Yb: YAG crystal in this paper. Then, based the ultrafast scintillation mechanism above, the influences of temperature, Yb3+ concentration, size of cation site, high energy ray irradiation and post-treatment on ultrafast scintillation were also discussed in detail. Aiming at the existing problems of Yb: YAG ultrafast scintillation crystal, this paper presented corresponding explanation and the method of co-doped cation to influence the charge density distribution around so that to improve the scintillation properties. At last, we prospected the development direction of Yb: YAG ultrafast scintillator in the future.关键词：Yb: YAG;ultrafast scintillation;scintillation mechanism;co-doped cation245|522|1更新时间：2020-08-12
- 摘要：A series of γ-Ca2SiO4: xCe3+,yAl3+ yellow phosphors were prepared by high temperature solid-state reactions. The structure, morphology and optical properties of the phosphors were characterized by X-ray diffractometer, scanning electron microscope, laser particle size analyzer, and fluorescence spectrometer. The results show that β-Ca2SiO4 and γ-Ca2SiO4 samples form at 1200~1300℃ and 1350~1500℃, respectively. The structures of Ca2SiO4 don't change with Al3+ and Ce3+ doping. The luminescence intensity of γ-Ca2SiO4: 0.5%Ce3+,4%Al3+calcined at 1450℃ reaches the maximum. Under the excitation of 450 nm, a broad band emission centered at 565 nm is observed, which mainly corresponds to 5d→2F7/2 and 5d→2F5/2 transitions of Ce3+. The luminescence intensity of phosphor is influenced by temperature, and it decreases by 37% as the temperature increases from room temperature to 475 K. The decay curves of Ce3+ can be fitted as the single exponential function. The fluorescence lifetime of the phosphor is 104.2 ns, which is basically consistent with the transition types as well as ionic valence of Ce3+.关键词：Ca2SiO4;yellow phosphor;luminescence property145|36|1更新时间：2020-08-12
- 摘要：LTL type zeolite crystals with regular morphology, high crystallinity and different aspect ratio were successfully synthesized by adjusting the composition of the synthesis gel. Then, the organolanthanide complexes were loaded inside of the zeolite LTL channels, denoted as zeolite LTL/Eu-TTA, by using the ‘ship-in-bottle’ method. The luminescence spectra analysis results show that the zeolite LTL/Eu-TTA crystal with 0.2 aspect ratio has the strongest emission of 5D0→7F2 located at 617 nm, whereas the crystals with aspect ratio of 3 has the weakest one under the excitation of 350 nm. Finally, The fluorescent array extending to the centimeter scale was fabricated in an oriented way by rapid wiping the zeolite LTL/Eu-TTA crystals with 0.2 aspect ratio in 10 s on the surface of PEI coated glass substrate. SEM results prove that nearly all zeolite LTL crystals compact closely with their c-axial perpendicularly to the glass surface in a monolayer manner. This one-dimensional orientated fluorescent array can issue bright red light under the excitation of 365 nm.关键词：zeolite LTL;manual assembly;fluorescent array;organolanthanide complexes140|169|0更新时间：2020-08-12
- 摘要：Two blue luminescence materials 2-phenyl-1H-phenanthro[9,10-d] imidazole (Phen-PI) and 2-pyridin-2-yl-1H-phenanthro[9,10-d] imidazole (Pyri-PI) were synthesized. The photophysical properties demonstrated the emission peaks of Phen-PI and Pyri-PI are 371.5, 388.5 and 403.5 nm, the photoluminescent quantum yield is 0.383 and 0.528, the fluorescence decay lifetime is 3.87 ns and 3.68 ns. The Frontier molecular orbital compositions and distribution for Phen-PI and Pyri-PI were calculated by using density functional theory (DFT). The results indicate that the introduction of pyridyl group to phenanthro[9,10-d] imidazole makes HOMO and LUMO of Pyri-PI decline 0.09 eV and 0.23 eV respectively, the energy gap between HOMO and LUMO decrease 0.14 eV, which can explaine the red-shift of Pyri-PI emission in theory.197|74|1更新时间：2020-08-12
- 摘要：Single-component CS and RB nano-films and two-component CS/RB nano-films were fabricated by low vacuum physical vapor deposition (LVPVD) method. Fluorospectro photometer, XRD and SEM were used to characterize the fluorescence, structure and surface morphology of the nano-films. Compared with the powder samples, the fluorescence emission peaks of the nano-films are more, the full widths at half-maximum of the peaks are larger, and the emission wavelength range exceeds 120 nm. The novel fluorescence of the nano-films is caused by the non-crystal state of aggregation of organic low-weight molecules and the effect of the nano layered structure.关键词：LVPVD method;organic fluorescent film;tunable fluorescence98|81|2更新时间：2020-08-12
- 摘要：We consider the pulse compression of higher-order solitons in two cascaded single-mode fibers. The two single-mode fibers have different anomalous dispersion value. When the higher-order soliton pulse achieves maximal compression in the first fiber, by switching the fiber with different dispersion, the pulse is compressed again as a new higher-order soliton in the second fiber. Each fiber length is optimized in order to achieve maximal compression inside each fiber segment. Based on the generalized nonlinear Schrdinger equation, we numerically study the effect of initial frequency chirp on pulse compression of higher-order solitons. Our numerical results show that initial frequency chirp has significant influence on higher-order solitons pulse compression. In comparison with the case of without initial chirp, a positive chirp can enhance the pulse compression and can reduce the pedestal energy in each fiber segment, while a negative chirp does the opposite. In each fiber segment, as the chirp parameter Cp increases, the compression factor increases, while pedestal energy and optimal fiber length decrease.关键词：nonlinear optics;optical pulse compression;optical solitons;chirp141|154|2更新时间：2020-08-12
- 摘要：A watt-class quasi-continuous 351 nm ultraviolet laser was fabricated by using frequency-doubled and frequency-tripled the radiation at 1053 nm from laser diode (LD) end-pumped Nd: YLF crystal under acoustic-optical Q-switched in a simple V-shaped cavity with two LiB3O5(LBO) crystals. An average output power at 351 nm of 1.12 W is obtained at repetition rate of 1 kHz and pumped power of 14 W. The single pulse energy is 1.12 mJ with the pulse width of 34 ns at 351 nm, and the peak power is up to 32.94 kW. The optical-optical conversion efficiency is 8%, and the electro-optical conversion efficiency is 3.4%. The beam quality is satisfactory.关键词：laser;351 nm ultraviolet laser;acousto-optical Q-switch;Nd: YLF crystal128|164|1更新时间：2020-08-12
- 摘要：Most of the oxide thin film transistor (TFT) need thermal annealing process to improve its performance, which is detrimental to their applications in the flexible display devices. Concerning this problem, a new TFT structure with room temperature process was presented, which has good performance without annealing treatment. AZO/Al2O3 stacked thin film was prepared by pulsed laser deposition as a channel layer. The stacked TFT showed better performance than single-layer AZO-TFT. The field effect mobility and on/off current ratio were 2.27 cm2·V-1·s-1 and 1.43×106. By analyzing the thickness, density, roughness, phase and band structure of AZO/Al2O3 stacked thin film, it is found that the electrons can be confined in the potential well of AZO, which forms a two-dimensional electron transport to improve the performance of TFT device.关键词：stacked thin film transistor;room temperature process;two-dimensional electron transport140|149|1更新时间：2020-08-12
- 摘要：An estimation method for the junction temperature of LED devices based on bidirectional thermal model was proposed in this paper. The bidirectional thermal model obtained in thermal measured procedure was applied to the original PET theory to predict the luminous flux. For the junction temperature, the average deviation between the unidirectional model and the measurement is about 11.2% and that between the bidirectional model and the measurement is 5.3%. For luminous flux, the average deviation between the PET theory with bidirectional model and the measurement is 6.3%. The calculated results are in good agreement with the measurements. These results confirm that the PET theory with bidirectional thermal model can provide accurate predictions for luminous flux.关键词：light-emitting diode;photo-electro-thermal theory;bidirectional thermal model;junction temperature;luminous flux101|190|0更新时间：2020-08-12
- 摘要：The circadian action factor (CAF) model was adopted to study the non-visual biological effects for the three-primary color-tunable white LEDs by calculating CAFs at various driving currents. In order to obtain the white light similar to the natural light according to non-visual biological effects, the models of CAF versus current and CCT versus current were generated. Therefore, the driving currents of three-primary LEDs could be determined after the CAF and the CCT of the natural light were known. Based on aforementioned models, and after the natural light at different times in a day was tested, the driving currents of three-primary LEDs were deduced. Then, driven by these currents, white LEDs were tested and their CAFs were calculated. A comparison between calculated values and experimental counterparts shows that the difference lies within 1.1%, suggesting the feasibility of this approach. This work appears meaningful for mimicking the natural light by using three-primary white LEDs.关键词：non-visual effects;RGB LEDs;circadian rhythms factor;natural light129|255|6更新时间：2020-08-12
- 摘要：To improve the display effect of LED screen, the variable control method was adopted to analyze what to cause the large deviation of white balance color temperature of LED screen based on new type of LED testing data of optical property. Firstly, the effect of the color coordinates and brightness of monochrome RGB on the white balance color temperature was analyzed. Then, the parameters that mainly affected the color temperature deviation were found from univariate analysis, and double partial analysis was conducted. Finally, the data validation of variable analysis was performed. The results show that the red chip brightness (Lr), blue chip brightness (Lb) and blue chip coordinates (Yb) are the main causes to influence white balance color temperature of LED screen. To confine the deviation of white balance color temperature to range ±500 K, Lr deviation must be less than 11%, Lb deviation must be less than 14% and Yb deviation must be less than 0.006 under the condition of single partial. Moreover, the corresponding control indexes were given under the condition of double partial. This study is expected to be applied in many related fields including LED spectral chip sorting, white light illumination and color deviation adjustment of LED screen with low current or small interval.关键词：variable control method;white balance;single deviation;double deviation;color deviation adjustment119|135|2更新时间：2020-08-12
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Current Density and Irradiance Distribution of Light-emitting-diode-array Device with Divided Pixels
摘要：When a 300 μm×300 μm chip is divided into 3×3 small chips with 20 μm adjacent spacing, the total saturated output power enhances up to 5.19 times and the maximum inject current increases 7 times nearly. The consequences indicate LED chip with smaller pixels array can possess greater inject current and higher saturated output power than the primary chip. Meanwhile, the effects of chips number and LED chips distance for irradiance distribution on target plane illuminated by multi-LED chips are studied. The irradiance uniformity reaches its peaks when LED chip-to-chip distance equals to maximum flat condition dmax. In addition, the irradiance uniformity area is increasing when the number of LED chips increasing. When the target plane is illumined by nine 300 μm×300 μm LED chips with distance dmax and each chip is divided into nine 80 μm×80 μm smaller pixels, the irradiance value is 3 times as primary LED chips array while the uniformity of irradiance not changing.关键词：LED arrays;current density;chip size;chip-to-chip distance;irradiance120|73|5更新时间：2020-08-12 - 摘要：Within the framework of effective mass approximation, the scattering rate and the mean scattering rate for two electrons and multiple electrons initially in the first excited subband and finally in the ground subband in GaxIn1-xAsyP1-y/InP stepped quantum well were calculated adopting the shooting method and Fermi's golden rule. The results show that the electron-electron scattering rate and the mean scattering rate increase with the increasing of Ga composition and well width, decrease with the increasing of As composition. The scattering rate decreases with the increasing of initial electron energy and intensity of applied electric field. The mean scattering rate increases with the increasing of carrier density. The electron temperature does not have great influence on the mean scattering rate, the mean scattering rate decreases slightly as the electron temperature rises. The calculated results can provide theory basis and guiding significance for the design of optoelectronic devices based on stepped quantum well and GaInAsP/InP material.关键词：GaxIn1-xAsyP1-y/InP;stepped quantum well;electron;Fermi's golden rule;scattering rate118|190|0更新时间：2020-08-12
- 摘要：The interaction between transferrin (TRF) and cefotaxime sodium (CEM) at different temperatures (298, 310 and 318 K) was studied by using UV absorption spectroscopy, traditional fluorescence spectroscopy, synchronous fluorescence spectroscopy and circular dichroism spectroscopy. The experiment results indicate that the fluorescence of TRF is regularly quenched with the addition of CEM. The quenching pattern is static. TRF and CEM are combined by electrostatic interaction, and new compound forms during the process. These different methods verify the accuracy and rationality of the results. In addition, synchronous fluorescence spectroscopy and circular dichroism spectroscopy both show the conformation of TRF is influenced by CEM.关键词：interaction mechanism;transferrin;spectroscopy;cefotaxime sodium115|200|1更新时间：2020-08-12
- 摘要：In order to verify the feasibility of the software simulation on road lighting characteristics, the road illuminations of several kinds of LED street lamps with different light distribution curve were measured, according to their simulation results and standard methods. By comparison, it is found that the ratios of actual illumination to simulation value are equal for different test points on the same road. Further calculations indicate that the both illuminance uniformity are the same. These results show that simulation software can accurately reflect the road lighting conditions. Besides, the luminous decay performance of the road lamps was also studied. The results show that the lamps with better heat dissipation performance decay more slowly and work longer.关键词：LED street lamps;road illumination;illuminance uniformity;luminous decay performance135|160|2更新时间：2020-08-12
- 摘要：Visible-near infrared spectroscopy (Vis/NIRS) is proved to be an effective tool in the prediction of soil properties. Wavelength optimization plays an important role in the construction of Vis-NIRS prediction model. In this article, a total of 130 topsoil samples collected from Guoyang County, Anhui Province, China, were used to establish a Vis-NIRS model for the prediction of organic matter content (OMC) in line concretion black soils. Through comparison, the combined spectral pretreatments of smooth and multiplicative scatter correlation (MSC) were applied to minimize the irrelevant and useless information of the spectra and increase the correlation between spectra and the measured values, and subsequently, SPXY methods were used to select the representative training set. Successive projection algorithm (SPA) and genetic algorithm (GA) were then conducted for wavelength optimization. Finally, the principal component regression (PCR) model was constructed, in which the optimal number of principal components was determined using leave-one-out cross validation technique. Results show that: both SPA and GA can significantly reduce the wavelength and favorably increase the accuracy, especially, GA can greatly improve the prediction accuracy of soil OMC, with Rcc, RMSEP and RPD up to 0.9316, 0.2142, 2.3195, respectively. Conclusively, using appropriate wavelength optimization methods, not only the computational load can be significantly reduced but also the prediction precision can be improved.关键词：visible-near infrared spectroscopy(Vis-NIRS);organic matter content (OMC);spectral pretreatments;sample selection;wavelength optimization119|109|1更新时间：2020-08-12
- 摘要：As a complex mixture of components, petroleum is difficult to be qualitatively identified by conventional detection methods. In this paper, the mixture of gasoline, kerosene and diesel was used to simulate the oil pollutants in the environment. The gasoline, kerosene and diesel could emit fluorescence with the material self information under the excitation of the specific wavelength range, and the fluorescence intensity was directly proportional to the concentration of the substance from the Lambert-Beer law, which was used to identify the kind of the oil. These samples were measured by FS920 steady state fluorescence spectrometer. The data were added to five-dimensional array data by Savitzky-Golay method, then the fourth-order date that contained complex information is obtained to analyze applications. A fourth-order correction method, which coupled unfolded partial least-squares to residual quadrilinearization, was proposed to deal with the five-way data. In order to test its predictive ability, the parallel factor method was used as a reference. Both of them can retrieve the excitation and emission profiles from the test samples. However, the REP value shows that the new method has higher precision than parallel factor analysis.关键词：qualitative identification;five-way data;unfolded partial least squares method;parallel factor method109|202|1更新时间：2020-08-12
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