最新刊期
卷 35 ， 期 12 ， 2014
- 摘要：MgxZn1-xO:Ga (x=0, 0.03, 0.14) films were prepared by metal organic chemical vapor deposition method. The transmission spectra of MgxZn1-xO:Ga films were measured. The optical band gap shows blue shifting on the transmission spectra with the increase of letter x. 12 pairs of interdigital electrodes were prepared on all MgxZn1-xO:Ga films. I-V curves of MgxZn1-xO:Ga films were measured at different temperature, and the temperature resistance curves of MgxZn1-xO:Ga films were obtained under certain voltage. The normalized R-T curve shows that the resistance of MgxZn1-xO:Ga films increases with the increasing of x at the same temperature. It is attributed to that the width of bandgap expands with the concentration of Mg ions, which leads to reduction of carrier concentration. The ionization energy for shallow donor impurities in the MgxZn1-xO:Ga lattice was calculated. When the mole fraction of Mg is 0, 3% and 14%, the ionization energy for shallow impurity is 45.3, 58.5 and 65 meV, respectively. The data show that the ionization energy for Ga donor obviously increases with the increasing of Mg concentration .关键词：MgZnO;Ga doped;ionization energy;resistivity114|103|0更新时间：2020-08-12
- 摘要：Highly crystallized Sm(TTA)3Phen with small size and uniform morphology was prepared by a rapid and efficient microwave-ultrasound technology. Frontier FT-IR/FIR spectrometer (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FSEM), and photoluminescence (PL) spectra were employed to characterize the samples. The relationships among reaction time, relative crystallinity, particle morphology and fluorescence properties were discussed. The results indicate that the highly crystalline Sm(TTA)3Phen can be successfully synthesized by microwave-ultrasound method. The optimum reaction time is 4 h for typical triclinic crystal powder with size of 5 μm, which has 72% highly-crystalline and good luminescence property. When the samples were tested after 90 d, the fluorescence decayed. The higher the crystallinity is, the less fluorescence decreases.关键词：microwave;ultrasound;rare earth organic complex;Sm(TTA)3Phen104|69|0更新时间：2020-08-12
- 摘要：KLa(MoO4)2:Sm3+ phosphors were prepared via high temperature solid state reaction. The crystal structure of the products was characterized via XRD technique, and it was found that all the obtained samples with various Sm3+ concentrations exhibited monoclinic phase. The excitation and emission spectra for the samples were measured, and broad excitation bands in ultraviolet and blue-greenish region were observed, meanwhile four emission peaks were detected when the samples were excited at 404 nm. The emission spectra and fluorescence decays at various temperatures were measured, and the mechanism for fluorescence temperature quenching was analyzed. Furthermore, the crossover process was confirmed to be responsible for the temperature quenching. Finally, Arrhennius equation was used to fit the experimental data and the activation energy was derived to be 0.48 eV. This result implies the excellent luminescent thermal stability of the studied phosphors.关键词：KLa(MoO4)2:Sm3+;red phosphor;temperature quenching;crossover131|266|2更新时间：2020-08-12
- 摘要：A series of BaZnF4:Er3+,Yb3+ upconversion luminescence nanoparticles with various doping concentrations were synthesized via thermal decomposition method. X-ray diffraction (XRD), transmission electron microscope (TEM) and fluorescence spectrophotometer were used to investigate the morphology, crystal structure and upconversion properties of the samples. The morphology of the sample is ball shape with an average size about 8 nm. 4%Er3+and 20%Yb3+ are the best doping mole fraction. Red and green emissions were observed for the synthesized samples under 980 nm excitation. The red and green emissions are corresponding to the transitions 2H11/2→4I15/2 (Green), 4S3/2→4I15/2 (Green) of Er3+, 4F9/2→4I15/2 (Red) of Er3+ ions, respectively.关键词：rare earth doping;BaZnF4;thermal decomposition;upconversion luminescence108|97|0更新时间：2020-08-12
- 摘要：Hydrothermal etching method was employed to prepare iron-passivated porous silicon (IP-Si) samples with peak energy around 2.0 eV and FWHM of 0.40 eV. As the excitation wavelength increases from 240 to 440 nm, the peak energy of photoluminescence red-shifts first, and then blue-shifts before it reaches a constant energy. The changing curve demonstrates a spoon-like pattern. By analyzing the statistics results from 15 IP-Si samples, it is found that the turnover excitation wavelength corresponding to the peak energy is about 330 nm and the related photon energy is 3.8 eV. The spoon-like relationship found between the peak energy and excitation wavelength is in good agreement with the photoluminescence behavior under the combined action of two types of non-bridging oxygen hole center of ≡ Si—O↑ and ≡ Si—O↑…H—O—Si ≡.关键词：porous silicon;iron passivated;photoluminescence;non-bridging oxygen hole;hydrothermal etching95|125|0更新时间：2020-08-12
- 摘要：KSr4(BO3)3:xEu2+(KSB:xEu2+) phosphors were synthesized by solid-state reaction method. The phase, morphology, and luminescence properties of the samples were characterized by using XRD, SEM, and photoluminescence spectra. XRD results show that the as-prepared samples are orthorhombic KSr4(BO3)3 single-phase. When x=1.5%, two broad bands are observed from 250 to 550 nm in the excitation spectra, which are attributed to 4f7-4f65d1 transition of Eu2+. Under the excitation of 400 nm, the emission spectrum shows an asymmetric yellow emission band around 560 nm, attributed to 4f65d1-4f7 transition of Eu2+. Because of three Sr crystallographic sites in KSr4(BO3)3 compound, one can infer that the asymmetric emission results from multiple Eu2+ centers by the spectral characteristics.关键词：KSr4(BO3)3:Eu2+;LEDs;phosphor123|81|0更新时间：2020-08-12
- 摘要：NaYF4:Eu3+ fluorescence powders were synthesized by mild hydrothermal method using EDTA-2Na as the complexing agent or sodium citrate as the assistant agent. Some physical properties were characterized by powder-X-ray diffraction (XRD), scanning electron microscopy (SEM), flourescence spectra, and FT-IR. XRD results show that all the samples synthesized at 140 ℃ for 24 h are pure hexagonal phase NaYF4. SEM images indicate that the as-prepared NaYF4:Eu3+ is uniform microsphere with diameter of about 20 μm using EDTA-2Na as the complexing agent, while hexagonal prism microrod with length of 1.8 μm using sodium citrate as the assistant agent. EDTA-2Na and sodium citrate, as assistant agent introducing into the reaction system, play a critical role in the morphology control. The morphology of the microsphere and hexagonal prism microrod is determined by the complexation of EDTA-2Na and the selective adsorption of sodium citrate, respectively. The samples mainly emit blue-white light under 395 nm excitation. The fluorescence intensity of NaYF4:Eu3+ microsphere is much stronger than that of microrod.关键词：NaYF4:Eu3+;hydrothermal synthesis;microsphere;fluorescence127|112|3更新时间：2020-08-12
- 摘要：This paper reports the experimental study of multiphonon relaxation (MR) involving a large energy gap (5 800 cm-1) crossover from bulk to nanocrystal (NC) system. The temperature dependence of MR rate for 5D3→5D4 of Tb3+ in β-NaGdF4:Tb3+ NCs was analyzed in a single-frequency approximation of phonon spectrum in the framework of the nonlinear theory of MR. The experimental data well agree with the theoretical curves within the range of 12 K to 312 K. It is shown that MR occurs predominantly via high-energy optical phonons. In Rayleigh limit, assuming that the Tb3+ emitter was located at the center of a nanosphere, the spontaneous decay rate Γrad was calculated using Green tensor approach. No significant variation in the local density of states (LDOS) was found inside the nanospheres. However, for R<35 nm, a new Gaussian distribution of LDOS was obtained based on Chew's theory outside the nanospheres.关键词：multiphonon relaxation;local density of states;β-NaGdF4:Tb3+ dielectric nanosphere;spontaneous-decay rate123|38|0更新时间：2020-08-12
- 摘要：Pt/TiO2 nanocomposites with three different TiO2 morphologies (nanocup, (001) nanosheet, (100) nanosheet) were prepared for removing dye from wastewater. Transmission electron microscopy results confirmed the formation of nanocup, (001) nanosheet, (100) nanosheet of TiO2 and the presence of Pt nanoparticles attached on TiO2 nanostructure. All TiO2 samples are anatase indicated by X-ray diffraction. The as-prepared Pt/TiO2 nanocomposites were used as adsorbent to remove dye from wastewater using the organic dye Rhodamine B as adsorbate. The nano-cup Pt/TiO2 sample exhibited the best efficiency on the degradation rate of Rhodamine B, and the removal ratio of the dye gets to 99.1% less than 1.5 h. Adsorption kinetics and isotherm were investigated and the possible mechanism of the different photocatalytic efficiency was suggested.关键词：Pt/TiO2;photocatalysis;nanocup;nanosheet94|117|2更新时间：2020-08-12
- 摘要：The electronic structures and optical properties of Li-doped ZnO systems were studied by the first-principle approach based on the density functional theory. The obtained results indicate that the band gap increases linearly and the absorption edge shifts to the short wavelength direction with the increasing of Li doping concentration. Due to the impurity absorption, a new absorption peak near the visible region in the doped system was observed. The absorption rate in visible light region can be promoted by suitable doping. Thus, the photocatalytic properties of system can be improved.关键词：ZnO;Li doping;electronic structure;optical properties;first-principles107|241|1更新时间：2020-08-12
- 摘要：Low Ohmic contact layers with the specific contact resistance of 4.5×10-5 Ω·cm2 were fabricated on the organic layer surface of PTCDA/P-Si photodetector chip. The electronic states of the interface of Al/Ni/ITO structure Ohmic contact layer were investigated using X-ray photoelectron spectroscopy (XPS). In ITO, In3d and Sn3d arise two peaks of split level, respectively. They are the binding energy of In and Sn atom located in oxidizing environment. Ni2p has two spectra peaks of Ni2p(1) and Ni2p(2). The lower binding energy location is Ni2p(1) which is excited by X-ray. It indicates that no chemical reaction happens between Ni and ITO layer, and the formation of A12O3 has been prevented. As for Ni2p(2) peak, it indicates that Al3Ni alloy phase has formed,which is good for the formation of low resistance Ohmic contact layer.关键词：organic photodetector;low-resistance Ohmic contact layer;reaction mechanism;X-ray photoelectron spectroscopy94|190|1更新时间：2020-08-12
- 摘要：Red phosphorescent microcavity organic light-emitting device (MOLED) with structure of Glass/DBR/ITO/MoO3(1 nm)/TcTa(55 nm)/CBP:Ir(piq)2acac(44 nm, 6%)/TPBI(55 nm)/LiF(1 nm)/Al(80 nm) was fabricated. For comparison, an OLED without cavity also was fabricated. The effect of microcavity structure on luminescent properties of phosphorescent devices was studied. The electroluminescence (EL) spectrum peak of OLED is at 626 nm, and the full width at half maximum (FWHM) is 92 nm. The electroluminescence (EL) spectrum peak of MOLED is at 628 nm, and the FWHM is 42 nm which is narrowed half compared with the 92 nm value. The micro cavity structure can narrow the luminescence spectrum of OLED and improve the colour purity. For MOLED, the maximum brightness, the maximum current efficiency, the maximum external quantum efficiency (EQE) are 121 000 cd/m2, 27.8 cd/A and 28.4%, respectively. For OLED, its maximum brightness, current efficiency and external quantum efficiency are 54 500 cd/m2, 13.1 cd/A and 16.6%, respectively. Comparing with the no cavity device, the luminescence properties of microcavity device have been improved greatly.关键词：organic light-emitting device(OLED);phosphorescent;microcavity157|187|1更新时间：2020-08-12
- 摘要：A fabrication method of transparent thin-film transistors based on Sb2O3/Ag/Sb2O3 (SAS) multi-layer transparent conductive film is developed by self-assembling diffraction. A self-assembled channel between SAS source/drain electrodes was formed by electron beam thermal evaporation in the one-shadow-mask process. The multi-layer transparent conductive film has desirable photoelectrical properties. Consequently, we obtained high performance devices with mobility of 11.36 cm2/(V·s) and an average visible range transmittance of 80%. Our results demonstrate that such transparent device is promising for low-cost optoelectronic product.关键词：transparent conductive film;Sb2O3/Ag/Sb2O3 multilayer;self-assembled channel;transparent thin- film transistors114|76|0更新时间：2020-08-12
- 摘要：Computational fluid dynamics (CFD) simulation and experimental analysis are presented for a semiconductor laser bar, which is cooled by a 5-layer oxygen-free copper micro-channel heat sink. A fluid-solid coupling conjugate heat transfer model is built for the micro-channel cooler and 10 mm-wide, 1.5 mm-cavities long bar. The curves of thermal resistance and pressure drop to flowing rate are plotted. The temperature of the laser bar and the characteristic of the cooling water are studied at 300 mL/min flowing rate. An experimental testing is performed for the thermal resistance and pressure drop of an 808 nm laser, which is packaged with the micro-channel cooler. The simulation results consistent with experiment. In the flowing rate of 300 mL/min, the thermal resistance is 0.38 ℃/W, which can dissipate a continuous 90 W heat below 70 ℃.关键词：semiconductor laser;CFD;micro-channel cooler;thermal resistance143|265|5更新时间：2020-08-12
- 摘要：5-(4-aminophenyl)-10,15,20-triphenyl-porphyrin (H2ATPP) was prepared and covalently connected to mesoporous silica thin films. Based on the porphyrin compounds's characteristic of being sensitive to acid and base, the molecular logics of RS-latch for sequential logic were achieved. The molecular logics have the advantages of larger surface area, periodic arranged uniform pore structure, and high transmission because of the covalent connection of porphyrin compounds to mesoporous silica. This hybrid mesoporous structure is not only advantageous to the interaction between the inputs and response materials, but also advantageous to the separation of the response materials and inputs without information loss.关键词：porphyrin;molecular logic;mesoporous silica thin film;covalently connected;RS-latch99|89|0更新时间：2020-08-12
- 摘要：2,7-dibromo-9,9-bis(3-propylamide-2-methylpropane sulfonic acid) fluorene (FSO3H) was synthesized by Michael addition reaction. Then, sulfonated polyfluorenes, poly[9,9-bis(3-propylamide-2-methylpropane sulfonic acid) fluorene] -alt-poly(9,9-dihexyl-fluorene) (PF6SO3H) and poly[9,9-bis(3-propylamide-2-methyl propane sulfonic acid) fluorene]-alt-poly(4,4'-diphenyl) (PFDBSO3H) were synthesized by Suzuki Coupling. The structure and properties of sulfonated polyfluorenes were investigated by 1H NMR, gel permeation chromatography (GPC) and UV-visible absorption spectroscopy. Photoluminescence performances of polyfluorenes under various conditions were studied. The results show that these copolymers have high molecular weights and can dissolve in methanol and water/methanol mixture. The photoluminescent wavelengths of the sulfonated polyfluorenes are red shifted with the increasing of polarity of the solvents. The fluorescence intensity of the polyfluorenes increases with the increasing of the polyfluorenes concentration under low concentration. Under high concentration, the quenching effect can be observed. A gradually increasing trend of fluorescence intensity is found when pH varied from 1 to 7.5, and a reduction in fluorescence intensity even completely quenching is observed when the pH changed from 7.5 to 12.5. Ions, such as Mv+, Ag+, K+, Na+ and Li+ have quenching effects on the fluorescence of polyfluorenes. The quenching effect of metal ions on PF6SO3H shows much stronger than on PFDBSO3H because of the more rigid backbone of PF6SO3H and the interaction between the polymer and the ions.关键词：sulfonated polyfluorenes;fluorescence spectrum;fluorescence quenching;ion microprobe96|132|0更新时间：2020-08-12
- 摘要：The photonic crystal multiple quantum well structure made of two kinds of single-negative materials was investigated by transfer matrix method. It is demonstrated that the resonance tunneling modes are weak dependence on incident angle and polarization. The number of the resonance modes can be controlled by adjusting the periodic structure of the constituents, and the quality factors of the resonance peaks can be greatly improved by increasing the scaling of the barrier photonic crystals. When the losses of two kinds of single negative media are taken into account, the effects on the resonance modes are striking difference.关键词：single-negative material;multiple quantum well structure;photonic crystal83|160|2更新时间：2020-08-12
- 摘要：For the limited power capacity problem of single photoconductive antenna, we use photoconductive antenna power combining technology to research high power and ultra-broadband terahertz radiation. By constructing a power combining system of three-way photoconductive antenna, using 500 μm aperture dipole photoconductive antenna as the object, we studied the power combining technology. When the optical path differences of terahertz emitted by three-way 500 μm aperture photoconductive dipole antenna are the same, the power combined time-domain spectral reaches to maximum peak, the degree of temporal coherence up to 90.6%, the output power of terahertz is improved efficiently.关键词：terahertz;photoconductive antenna;power synthesis105|175|2更新时间：2020-08-12
- 摘要：During the process of evaluating ICF micro-target image with the current image definition evaluation function, owing to the changes in image contrast of different components of micro-target, the evaluation function may lose its ideal curve characteristics easily. This may not only result in the decrease of focus accuracy but also, in some cases, the failure of the entire focusing process. Based on the analysis of the causes for the blurring defocused image, we discovered that the primary reason for defocused image was structural distortion. With the characteristic of Zernike moment of describing the image structure in mind, we propose a new function for evaluating the image definition of micro-target. The new evaluation function is consisted of Zernike moments weighting of different steps, and it is realized through the evaluation of image contrast for micro-targets of different definitions by regulating the weight coefficient. We confirm that the new evaluation function maintains the ideal curve characteristics during the process of evaluating the micro-target images compared to the current evaluation function. In the condition of low contrast, however, the new approach holds a distinct advantage in terms of sensitivity and noise immunity.关键词：ICF micro-target;image definition evaluation function;contrast;Zernike moment104|176|1更新时间：2020-08-12
- 摘要：The electroluminescence and infrared thermography were used to detect the defects of the solar cells by applying different forward bias and reverse bias voltage. The solar cell under forward bias mainly emits infrared light from 850 to 1 200 nm due to the recombination of electron and hole. The intensity of the emitted light depends on the series resistance and minority carrier diffusion length of the solar cell, so it can be used to detect the defects of finger disturbing, crack, and electrode etching, et al. The emission of light under reverse bias is intra-band emission which covers a wide spectrum from visible light to IR. The breakdown can be detected by reverse bias electroluminescence (RBEL). Only under high bias, weak Ohmic shunt appears in RBEL. Linear and nonlinear shunt can be detected using IR thermography under different bias. Strong Ohimc shunt can be detected in forward and reverse bias. The nonlinear shunt depends on the type.关键词：electroluminescence;solar cell;different bias;thermography102|251|5更新时间：2020-08-12
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