最新刊期
卷 35 ， 期 7 ， 2014
- 摘要：Three AlxGa1-xN samples were grown by metal organic chemical vapor phase deposition (MOCVD), and their optical properties were analyzed by the steady-state and time-resolved photoluminescence (PL) techniques. In view of the fact that the experimental phenomena cant be fully explained by a single mechanism of polarization electric field or that of local state, which remarkably influence luminescent properties of nitrids, the competition mechanism between local state and internal polarization electric field was proposed. By analyzing the experimental data, two crucial conclusions are drawn. First, the temperature starting point of PL peak blue-shift basically corresponds to the shift point between the effect of local state and the effect of polarization electric field. The temperature starting point of PL peak blue-shift is well consistent with the temperature point where the slope of illuminant intensity-temperature curve changes significantly. Then, there is non-uniform polarization electric field distribution in the sample if the PL peak has two blue-shifts with the temperature increasing in AlGaN alloy.关键词：illuminant intensity;local state;polarization electric field;temperature;AlGaN alloy117|216|0更新时间：2020-08-12
- 摘要：Reduced graphene oxide-ZnSe (r-GO/ZnSe) nanocomposites were successfully synthesized by an easy hydrothermal method. This process used the graphene oxide nanosheets as dispersant and two-dimensional growth template for ZnSe, resulting in the in situ formation of ZnSe nanoparticles on graphene oxide nanosheets and subsequent reduction of graphene oxide to r-GO. The samples were characterized by XRD, TEM, and FT-IR. The results show that the cubic ZnSe nanoparticles with the mean size of 30 nm distribute on r-GO sheets to form compact composites. UV-Vis absorption spectra indicate that the absorption edge of r-GO/ZnSe is at about 445 nm. PL spectra show a strong emission peak at 470 nm excited by 430 nm. The obtained r-GO/ZnSe nanocomposites may play important role in white LED field.关键词：reduced graphene oxide;ZnSe;nanocomposites;optical properties112|292|2更新时间：2020-08-12
- 摘要：The reddish-orange Ca3Y2-xSi3O12:xSm3+ phosphors were synthesized by the high temperature solid-state method at 1 400 ℃, and the effects of Sm3+ ion doping concentration and fluxes on the luminescence property of the phosphors were studied. The principal crystalline phase of the samples is Ca3Y2Si3O12. Ca3Y2Si3O12:Sm3+ silicate phosphors can be effectively excited in the range of 320~500 nm, and emit reddish-orange light. Excited by 402 nm, the emission peaks mainly locate at 562 nm (4G5/2→6H5/2), 598 nm (4G5/2→6H7/2), and 646 nm (4G5/2→6H9/2), The peak locating at 598 nm is the maximum. With the increasing of the doping concentration of Sm3+, the emission intensity of the phosphors increases firstly and then decreases. The optimum doping content of Sm3+ is x(Sm3+)=5%. The concentration quenching mechanism is the interaction among ions. The influence of several kinds of fluxes was discussed also. The emission intensities all decrease by adding a certain amount of NH4F, CaF2, NaCl, but increase significantly by adding H3BO3 with the optimum doping mass fraction of 1%.关键词：phosphors;reddish-orange light;Sm3+ doping;high temperature solid-state method;fluxes156|95|9更新时间：2020-08-12
- 摘要：The photocrosslinking properties of poly(4-methacryloyloxy-4'-dimethyl aminochalcone) (PMADMAC) and poly(4-acryloyloxychalcone) (PAC) homopolymers were investigated by Fourier transform infrared spectoscopy (FT-IR), thermogravimetric analysis, UV-visible spectroscopy (UV-Vis), and fluorescence spectroscopy. Photocrosslinking results of PMADMAC and PAC indicate the photo-induced [2+2] cycloaddition reaction takes place rapidly with the increase of light irradiation time and is carried out easily at presence of shortwave UV light. The photocrosslinking rate of polymers in the state of thin film is slower than that of solution due to the limited molecular motion in solid. Compared to PAC, the cycloaddition reaction of PMADMAC with intramolecular charge transfer properties takes place more easily and completely, and the photocrosslinking rate more rapidly. The photoluminescent properties were investigated by fluorescence spectroscopic techniques and the results show PMADMAC with solvent polarity sensitive fluorescence and PAC without fluorescence. With the increase of 365 nm UV light irradiation time, the fluorescent intensity of PMADMAC dilute solution decreases drastically and the fluorescent wavelength blueshifts in the late of UV irradiation. Thermogravimetric analysis results show a good thermalstability of PMADMAC and PAC, and a decrease in thermalstability after the formation of cyclobutane ring by photocrosslinking.关键词：poly(meth)acrylates;photocrosslink;chalcone;fluorescence145|237|0更新时间：2020-08-12
- 摘要：We have performed first-principles calculations based the framework of density-functional theory to determine the effects of Te doping on the band structure, density of state and photoelectric properties of single-layer MoS2. The calculated results indicate that the direct band-gap of pure single-layer MoS2 is 1.64 eV. The top of valence band is fundamentally determined by the S-3p and Mo-4d states, and the bottom of conduction band is occupied by the Mo-4d and S-3p states in the pure single-layer MoS2. Meanwhile, the indirect band-gap of Te-doped single-layer MoS2 is 1.47 eV, while the band gap of Te-doped single-layer MoS2 has decreased and the optical absorption has shown a red-shifted observably as compared with the pure single-layer MoS2, which provides important theoretical guidance for the applications of single-layer MoS2 in optical detectors.关键词：first-principles;single-layer MoS2;electronic structure;photoelectric properties119|349|8更新时间：2020-08-12
- 摘要：Excited-state processes in T4 organic dye-sensitized Al2O3 and TiO2 films were studied by femtosecond transient absorption spectroscopy and femtosecond time-resolved photoluminescence dynamics based on up-conversion method. By multiexponential analysis, we obtained the electron injection efficiency of 93% in T4 dye-sensitized TiO2 film. In addition, we further got the electron injection rate of 1.17 ps-1 in the T4 dye-sensitized TiO2 film by a static inhomogeneous electronic coupling model.关键词：organic dye;dye-sensitized;electron transfer117|130|2更新时间：2020-08-12
- 摘要：A stable and repeatable p-type ZnO is the key to realize the practical applications of photoelectric devices. Nitrogen has been considered as a possible acceptor dopant for p-type ZnO for a long time. However, the low solubility of nitrogen acceptor at oxygen site in ZnO is considered to be one of the main obstacles for p-type ZnO. In this paper, B/N co-doped p-type ZnO thin films were grown on sapphire substrate by plasma-assisted molecular beam epitaxy. The effect of boron on the nitrogen doping was studied by comparing with the single nitrogen doped thin films. X-ray photoelectron spectroscopy demonstrated there exists boron and B—N bond in the ZnO thin film. Compared to the single N-doped sample, B/N codoped samples present much higher carrier density. And the ZnO:(B,N) thin films show stable p-type conduction in two years. It is attributed to the increase of solubility of nitrogen acceptor. It benefits from the strong B-N bonding and weak donor character of boron at zinc site. Boron will not bring strong compensation for acceptors. It suggests that boron is a good co-doping candidate for nitrogen doped ZnO thin films.关键词：ZnO;B/N codoped;stable p-type conduction93|162|0更新时间：2020-08-12
- 摘要：Er3+/Yb3+ codoped and Tm3+/Yb3+ codoped laurustinus shaped NaY(WO4)2 microspheres were prepared via microwave assisted hydrothermal reaction. The XRD patterns indicated the resultant isbody-centered phase, and the SEM images showed the obtained samples are laurustinus shaped microspheres. In order to avoid the heating effect of high power infrared laser irradiation, the temperature sensing curve and sensitivity curve were obtained by using the down-conversion spectra at different temperatures under 380 nm excitation. Furthermore, a mixture with the weight ratio 1:10 of Er3+/Yb3+ codoped NaY(WO4)2 to Tm3+/Yb3+ codoped NaY(WO4)2 was prepared, and the upconversion emission spectra upon 980 nm excitation were measured. The laser irradiation induced thermal effect and the dependence of blue upconversion luminescence intensity on the irradiation time within 40 min were studied. It was found that the sample temperature was elevated at the initial time of laser irradiation, and then reached an equilibrium temperature. Additionally, it is also confirmed that the infrared laser irradiation affects the Tm3+/Yb3+codoped sample much more obviously than Er3+/Yb3+ codoped one.关键词：microwave assisted hydrothermal reaction;upconversion luminescence;temperature sensing;thermal effect151|38|1更新时间：2020-08-12
- 摘要：γ-zirconium phosphate(γ-ZrP) and a modified zirconium phosphate (γ-DDZrP)were prepared by direct precipitation method. Then, the chromophore pyrazinecarboxylic acid as guest molecules was intercalated into the modified zirconium phosphate. The changes of their layer spacing and spectroscopic properties were studied in detail. The results of X-ray-diffraction demonstrate that the interlayer spacing is reduced to 3.29 nm from 3.70 nm after intercalation. The fluorescence spectra show that the emission peak is blue shifted from 373 nm in aqueous solution to 366 nm in suspension. Furthermore, the fluorescence property of pyrazinecarboxylic acid assembled into lamellar framework is dramatically improved as compared to the chromophores in aqueous solution. As the chromophore concentration is 15 μmol/L, the fluorescence intensity is enhaced 6-fold. It is concluded that γ-DDZrP provides a special microenvironment which can improve the optical properties of chromophores.关键词：pyrazinecarboxylic acid;modified zirconium phosphate;hybrid assembly;fluorescence properties87|25|0更新时间：2020-08-12
- 摘要：It is significant to develop new cyclometalated iridium (Ⅲ) complexes with phenylquinoline derivatives because of their good luminescence property. Structure of these complexes were characterized by means of NMR and mass spectra. Photophysical properties were detected by means of ultraviolet spectra, fluorescence spectra and cyclic voltammetry(CV). The electrochemiluminescence properities were also studied. According to the ultraviolet and fluorescence spectra, the iridium(Ⅲ) complex 1[(pq)2Ir(phen)](PF6) and 2[(dpq)2Ir(phen)](PF6) emit yellow light centered at 554.5 nm and 566.5 nm, while the iridium(Ⅲ) complex 3[(pqcm)2Ir(phen)](PF6) and 4[(pqca)2Ir(phen)](PF6) emit red light centered at 621 nm and 618.5 nm, which are desirable for organic light-emitting device applications. Their quantum efficiencies are from 2.5% to 7.9%, and the complex 1 is as high as 7.9%. The ECL efficiency of 1 is the highest of all, which is 9.50 times than that of [Ru(bpy)32+]reference substance. The results suggest that the iridium complex 1 has a great application potential in ECL detection.149|323|1更新时间：2020-08-12
- 摘要：Sr3SiO5:Ce3+, Li+ phosphors were synthesized by the high temperature solid state reaction method. The crystal structure and luminescent properties of the samples were analyzed by X-ray diffraction and fluorescence spectrophotometer. Sr3-2xSiO5:xCe3+,xLi+ samples with tetragonal phase structure can be synthesized at 1 420 ℃. The excitation spectral distribution is in the near-ultraviolet range of 270 ~ 500 nm with two bands, and the double peak positions are located at 328 nm and 410 nm, respectively. The emission spectrum under 410 nm near-ultrviolet excitation shows a broad band centered at 528 nm. The optimum doping content of Ce3+ is x(Ce3+)=0.8%. With the increase of doping concentration, the luminescence intensity firstly increases and then decreases because of the concentration quenching effect. The concentration quenching is attribute to the dipole-dipole interaction of Ce3+, according to Dexter theory.关键词：solid state reaction method;Sr3SiO5：Ce3+;Li+;near-ultrviolet;dipole-dipole104|88|1更新时间：2020-08-12
- 摘要：Phosphorescent white organic light-emitting diodes with double light-emitting layers were fabricated based on phosphorescent blue emittor bis [3,5-difluoro-2-(2-pridyl)phenyl-(2-earboxypyribyl)iridumⅢ] (FIrpic) and red emittor bis(2-methyldibenzo[f,h]quinoxaline)(acetylacetonate) iridium(Ⅲ)(Ir(MDQ)2acac). FIrpic was doped in an ultra wide band-gap host 1,3-bis(triphenylsilyl)benzene (UGH3), and Ir(MDQ)2acac was doped in the host 4,4',4"-tris(carbazol-9-yl)triphenylamine(TCTA). A hole transporting wide-band-gap material 1,3-bis(carbazol-9-yl)benzene (mCP) was introduced between the emitting layers. The device structure was ITO/NPB(40 nm)/TCTA:Ir(MDQ)2acac 7%(10 nm)/mCP(x nm)/UGH3:Firpic 8%(30 nm)/BPhen(30 nm)/LiF(0.8 nm)/Al(200 nm). The results show that the interlayer plays an important role of balancing charge carriers, and blocking energy transfer between the emitting layers. With an appropriate thickness of the interlayer, the device performances can be significantly enhanced. Compared with the device without interlayer, the maximum current efficiency can be enhanced from 3.4 cd/A to 13.2 cd/A.关键词：white OLED;efficiency;interlayer;two-band;energy transfer119|134|1更新时间：2020-08-12
- 摘要：AlGaN/AlN/GaN HEMT structures were grown on sapphire substrate by MOCVD with different AlN growing time, and the influence of AlN thickness on electrical properties was investigated. When AlN growth time is about 12 s corresponding to the AlN thickness of 1~1.5 nm, the sample has the best performance of electrical properties with the lowest sheet resistance of 359 Ω·sq-1, the highest 2DEG concentration of 1.16×1013 cm-2, and a high 2DEG mobility of 1 500 cm2· V-1·s-1. AFM results indicate that AlN layer within a certain thickness range has little influence on the surface morphology. HRXRD results show that AlGaN/AlN/GaN HEMT has a good heterostructure interface.关键词：AlN thickness;PALE;MOCVD;HEMT;electrical properties171|325|0更新时间：2020-08-12
- 摘要：In order to restrain the scintillation effect in the course of laser transmitting through the atmosphere, the relation between the laser coherence and the scintillation index was researched. First, the mathematic model correlating with laser coherence was established based on the generation mechanism of scintillation effect. Then, the laser was divided into four beams, and the coherence was destroyed. On this basis, the atmosphere turbulence emulation experiment device was made using the random phase screen as core element, and the far field spot scintillation index with different laser coherence was evaluated. Experimental results indicate that the scintillation index with four beams reduce about 75% in comparison with single beam. So the availability of multiple partially coherent beams limiting laser intensity scintillation effect has been approved by the result of theory analyzing and experiment.关键词：scintillation effect;coherence;random phase screen;scintillation index103|116|5更新时间：2020-08-12
- 摘要：The principle of self-heating effect of AlGaInP micro-LED cells was analyzed. By analyzing the temperature distribution of each cell with square-circle electrode, the relationships of the internal quantum efficiency vs. anode current and the lattice device temperature vs. anode voltage were got. Under 2.2 V driving voltage, the thermal impedance of each layer was calculated and the effective thermal impedance was obtained as 96.7 ℃/W. After adding heat-sink to the device, the thermal impedance of the device with heat-sink structure was as low as 30.6 ℃/W in ideal condition. The results show that the thermal performance can be improved obviously with the designed heat-sink structure.关键词：AlGaInP;square-circle electrode;micro-arrays;thermal analysis;heat-sink structure92|210|1更新时间：2020-08-12
- 摘要：An organic/inorganic composite electrical bistable device with the sandwich structure of ITO/PVP/ZnO nanocrystal (NCs)/PbS nanocrystal (NCs)/PVP/Al was fabricated. Compared with the device structure of ITO/PVP/ZnO NPs/PVP/Al, the ON/OFF ratio of target device was improved by 2 orders of magnitude. The carrier transportation and resistance switching mechanism of device were discussed via I-V characteristics and the energy band structures of the devices. The effective capture/release of electrons could be attributed to the optimization of device structure and modification of ZnO NCs surface by PbS NCs layer.关键词：electrical bistable;ZnO nanocrystal;resistance switching mechanism;PbS nanocrystal modification layer102|68|0更新时间：2020-08-12
- 摘要：In order to realize the unltrasensitive analysis by using the surface enhanced Raman scattering (SERS), we presented a simple and reproducible approach to encapsulate the aggregation of 4-mercaptobenzoic acid-modified Ag nanoparticles with silica. In order to obtain "hot spot", the level of aggregation could be controlled by varying the concentration of NaNO3, and then the aggregation was coated with silica, which was demonstrated with SEM. In conclusion, the SERS signal seriously depended on the level of aggregation. Due to the strong enhancement effect, this technique has the potential in biomedical field.关键词：surface enhanced Raman scattering;Ag nanoparticles;hot spot;silica-coated153|152|6更新时间：2020-08-12
- 摘要：SiO2 coated ZnS:Mn quantum dots were synthesized and modified with PVP. The proce dure of modification was based on the effect between amido band of PVP and hydroxyl of SiO2. ZnS: Mn/SiO2/PVP quantum dots had an excellent fluorescence stability and colloid stability in sea water. Based on the fluorescence quenching of Pb2+ to ZnS:Mn/SiO2/PVP, a novel method for determination of Pb2+ in sea water was developed. With a concentration of 10-3 mol/L, the quenched fluorescence intensity of ZnS:Mn/SiO2/PVP is linearly in proportion to the concentration of Pb2+ in sea water from 10 to 100 μmol/L. The correlation coefficient R is 0.994 6, and the detection limit for Pb2+ in sea water is 8×10-7 mol/L.关键词：ZnS：Mn/SiO2/PVP quantum dots;fluorescence sensor;sea water;Pb2+ ions144|128|2更新时间：2020-08-12
- 摘要：A new-type 12 W LED bulb was proposed based on the cold spray technology and the integrated design of an aluminous heat sink to replace the traditional incandescent bulb. The heat sink was made of aluminum and manufactured by cutting and bending. The temperature fields for the different shape LED bulbs were simulated by ANSYS to obtain the optimal shape with the lowest temperature. The internal structure of the copper-based plate was analyzed. Meanwhile, simulation was performed to get the temperature fields with the different copper circuit layers. The results show that the junction temperature of LED decreases with the thickness of the copper circuit layer when the thickness of the copper-based plate keeps constant. The maximum junction temperature of the 12 W LED bulb is 71.252 ℃ lower than the safe temperature of 85 ℃. It implies that the new-type 12 W LED bulb could meet the requirements of heat dissipation and lighting habits.关键词：LED bulbs;aluminous heat sink;copper circuit layer;thermal analysis120|106|8更新时间：2020-08-12
- 摘要：A novel coupled-cavity waveguide based on two-dimensional triangular lattice photonic crystals was proposed. This structure was composed of the line-defect waveguides, resonant micro- cavity, and ellipse-holes which are located between line-defect waveguide and resonant micro-cavity. The band structure of line-defect waveguide was simulated by the method of the plane-wave expansion. The transmission characteristics and quality factor of the coupled-cavity waveguides were investigated by the finite-difference time-domain (FDTD) method. By optimizing the structural parameters such as amount, size, and arrangement of ellipse-holes between the resonant micro-cavity and the line-defect waveguide, a 90% transmission efficiency was obtained with a Q-factor of 104. Then, appropriate parameters were selected, a high Q-factor of 107 was achieved, the transmission efficiency corresponding to the resonance frequency was still above 60%.关键词：two dimensional photonic crystal;finite difference time domain method;Q-factor;transmission responses133|110|1更新时间：2020-08-12
- 摘要：Based on the birefringence effect, a novel duel-core photonic crystal fiber polarization beam splitter was proposed. Tellurite glass and SF6 glass were used as the material for the PCF, respectively. Using the full-vector finite element method (FEM), the effects of structural parameters on birefringence and relative coupling length were analyzed, and the characteristics of the splitters,such as coupling length, extinction ratio and bandwidth were simulated. The numerical simulation results demonstrate that the tellurite glass splitter has higher extinction ratio and bandwidth than the SF6 glass splitter. The extinction ratio of the tellurite glass splitter is -53.46 dB at the wavelength of 1.55 μm, and the bandwidth is over 120 nm when the extinction ratio is less than -20 dB.关键词：photonic crystal fibers;polarization splitter;full-vector finite element method;coupling length95|125|2更新时间：2020-08-12
- 摘要：An ultra-compact wavelength filter on silicon-based hybrid plasmonic waveguide is proposed and simulated. The present hybrid plasmonic structure needs only one layer to be patterned and is favorable for fabrication. The light is confined strongly in a thin silica dioxide layer between the metal substrate and silicon top layer. The filter consists of a stub structure coupled to a straight waveguide. The output spectra calculated by the 3D FDTD method are similar as those devices based on the 2D metal-insulator-metal waveguide structure in the previous literatures. In addition, the effects of the dimensions of the stub and waveguide structure on the device's performance are analyzed.关键词：surface plasmon;stub-type wavelength filter;silicon-on-insulator;hybrid plasmonic waveguide109|135|0更新时间：2020-08-12
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