最新刊期
卷 30 ， 期 1 ， 2009
- 摘要：The transmission properties of two-dimensional photonic crystals with triangular dielectric rods were studied using the finite difference time domain (FDTD) method for different lattice structures, section areas, azimuth angles and incident angles. The results showed that the photonic band gap (PBG) width and the central frequency depends on the lattice structure and sectional areas. Azimuth angle of cylinder affects the PBG in some degree, however the widths of band gaps are the same when their effective incident section are equal, such as with the θ value of 0° or 60°. In addition, transmission characteristics have no changes with the variation of incident angle in range of low frequency (below 0.26a/λ), but the transmission coefficient decreases dramatically with increasing frequency(0.28a/λ~0.37a/λ), even new wider forbidden band is formed under certain conditions. This work will be of significance in fabricating PC devices.关键词：two-dimensional photonic crystals;the finite difference time domain method;transmission characteristic;triangular dielectric rods118|124|0更新时间：2020-08-12
- 摘要：Fe3+, Ce3+ co-doped LiAlO2 samples were successfully prepared by solid-state reaction method. The XRD and the SEM results showed that tetragonal γ-LiAlO2 with diameter less than 10 μm was obtained. It was found firstly that the luminescence intensity of γ-LiAlO2 ∶ Fe3+ is enhanced greatly by introducing a small amount of Ce3+ ions. The Ce3+ plays a role as sensitizer in host lattice, resulting in the enhancement of deep red emission of Fe3+ ions. The improved phosphor might be widely applied to agricultural film and fluorescent lamps relating to plant growth.关键词：phosphor;luminescence;efficiency;co-doped121|182|0更新时间：2020-08-12
- 摘要：In,P codoped ZnO ∶ (In,P)] films were grown on quartz by radio frequency magnetron sputtering, the ZnO target was mixed with 1.5% P2O5 and 0.3% In2O3,and the mixing gas of Ar and O2 was used as the sputtering gas. The as-grown ZnO ∶ (In,P) film shows insulating conduction, but n-type conductivity after annealing at 600 ℃ for 5 min, and p-type conduction after annealing at 800 ℃ for 5 min. The p-type ZnO:(In,P) has a resistivity of 12.4 Ω·cm, a carrier concentrativity of 1.6×1017 cm-3 and a Hall mobility of 3.29 cm2·V-1·s-1 .XRD mea-surement indicates that both the as-grown and annealed ZnO ∶ (In,P) films have a preferred (002) orientation and larger (002) diffraction angles than that of undoped ZnO prepared at the same conditions, implying that both In and P occupy Zn site in the ZnO ∶ (In,P). The XPS result confirm that the P substitutes Zn site (PZn) but not O site in the ZnO ∶ (In,P). Therefore, it was suggested that both In and P substitute at Zn sites in the ZnO ∶ (In,P) and the PZn combines with two Zn vacancies(VZn) to form a PZn-2VZn acceptor complex, which is responsible to p-type conductivity of the ZnO ∶ (In,P).关键词：ZnO;codoping;RF magnetron sputtering;XPS107|131|1更新时间：2020-08-12
- 摘要：Slurry method based on a phosphor suspension in a water-soluble photoresist was discussed. A conformal-coating phosphor layer was deposited on the surface of LEDs. The luminous performance of power white LEDs was found to be mainly depending on the concentration and ratio of ingredients in slurry and the structure of coating layer. In this paper, the parameters were investigated and some advices, which were suggested to improve the performance, were proven to be effective in our experiment. The aging testing of LEDs with this slurry method showed that the luminous flux was 95.95% of that of the beginning after the LED was lightened for 168 h at 700 mA.关键词：white LEDs;slurry;extraction efficiency;packaging102|93|1更新时间：2020-08-12
- 摘要：Photonic crystal(PC) is a new artificial material. Its unique optical properties enable it to be used in fabricating novel optical devices. Optical power splitters made of photonic crystal waveguides are believed to become essential components for compact photonic integrated circuits. It can engender photonic crystal waveguide (PCW) in the complate two-dimensional photonic crystals by introducing line defects. We designed a 1×4 optical power splitter made of linear-defect waveguides in photonic crystals, and analyzed its properties using the finite-difference time-domain method. Results showed that the transmission properties vary with wave frequency and branch geometry, and that an incident wave is divided equally into four output parts. To reduce the reflections at the three Y-branching regions in the 1×4 splitter, we can adjust the radius of the medium cylinder in the branching region, and achieve high transmission for <em>R</em>=0.13<em>a</em> at each output waveguide. We analyzed the physical origins of this performance and this kind of multi-mode interference may find potential application in PC optical circuits.关键词：finite-difference time-domain method;photonic crystals waveguides;splitter113|155|1更新时间：2020-08-12
- 摘要：Propagation characteristic of two-dimensional triangular lattice photonic crystals in THz range was studied by using PWM. The band gap structure and density of photon states of two-dimensional triangular lattice photonic crystals constructed from air in Si dielectric matrix was calculated. It was found that when the radius was 0.47<em>a</em>, it can generate maximum absolute photonic band gap with 0.070 1 THz, and it can generate maximum photonic band gap with 0.102 2 and 0.192 3 THz when the radius was 0.49<em>a</em> and 0.45<em>a</em>, respectively. The photonic band structure was also shown by the photonic density of states. This research provides a theoretic basis for the development of THz devices.关键词：THz wave;photonic crystal;plan wave expansion method;triangular lattice111|152|0更新时间：2020-08-12
- 摘要：As novel functional materials, long afterglow phosphors have drawn more and more attention in recent years because of a constantly growing market for their applications in traffic signs, emergency signage, watches and clocks, textile printing, among others. Amid the newly developed long afterglow materials which have already found commercial use, green-emitting SrAl<sub>2</sub>O<sub>4</sub>∶Eu<sup>2+</sup>,Dy<sup>3+</sup> is of special interest because of its high quantum efficiency, good stability and excellent persistent luminescence combined with an easy proces-sability. However the mechanism of afterglow phosphors is still unclear, even the effect of the reductive using on the producing process on the luminescence is not well studied. In this paper, compounds of SrAl<sub>2</sub>O<sub>4</sub>∶Eu, Dy were prepared in air atmosphere by high temperature solid state reaction firstly, and then were treated in weak reductive atmosphere (95%N<sub>2</sub>+5%H<sub>2</sub>).Thirdly, in air atmosphere again, and finally, in weak reductive atmosphere (95%N<sub>2</sub>+5%H<sub>2</sub>). The effect of this process on the structure, luminescent properties, and themoluminescent spectra of the samples were studied by X-ray diffraction (XRD), fluorescent spectrophoto-meter and thermoluminescence dosimeter (TLD) respectively. The monoclinic structure remains the same irrespective of the process, and is in good agreement with that of the powder diffraction file (JCPDS) 34-0379 (SrAl<sub>2</sub>O<sub>4</sub>). The reduction of Eu<sup>3+</sup>→Eu<sup>2+</sup> was firstly observed in the aluminate phosphor of SrAl<sub>2</sub>O<sub>4</sub>∶Eu, Dy synthesized in air condition and the reductive mechanism was also discussed in this paper. Eu<sup>3+</sup> shows completely different luminescent properties with Eu<sup>2+</sup> in SrAl<sub>2</sub>O<sub>4</sub>. Eu<sup>3+</sup> has two narrow, intense spectra peaking at 592 nm and 612 nm, which resulted from the <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>1</sub> transition and <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>4</sub> transition respectively, implied that the Eu<sup>3+</sup> may occupy two different lattice sites in the host crystal lattice; while Eu<sup>2+</sup> has only one broad band spectra peaking at 513 nm, which resulted from the 4f<sup>6</sup>5d→4f<sup>7</sup> transition. The emission of Dy<sup>3+</sup> was not found in all the four samples, indicated that the Dy<sup>3+</sup> ions play a roll as trap centre in the phosphor, but not the luminescence centre. The concentration of Eu<sup>2+</sup> in the samples treated in weak reductive atmosphere greatly increased whereas the concentration of Eu<sup>3+</sup>greatly decreased when compared to the samples treated in air atmosphere. The samples treated in weak reductive atmosphere have much higher thermoluminescent peak than that of the samples treated in air atmosphere. But all the samples, irrespective being treated in air atmosphere or reductive atmosphere, have the same trap depth (about 0.65 eV), which derived from Dy<sup>3+</sup>. All these phenomena indicated that, for the long after-glow phosphor material of SrAl<sub>2</sub>O<sub>4</sub>∶Eu, Dy prepared in air atmosphere, the process of being treated in weak reductive atmosphere, air atmosphere and weak reductive atmosphere orderly, changes the valence of Eu ion and luminescence intensity, but doesnt change the trap depth in the material.关键词：long afterglow;strontium aluminate;europium;valence-change94|113|4更新时间：2020-08-12
- 摘要：Recently, most of interest in luminescent rare-earth ions have concentrated on one species: trivalent erbium, in particular its emission band around 1.5 μm. Because the 1.5 μm is the wavelength for telecommunications,and trivalent erbiums emission band around 1.53 μm offered several advantages including the capability to produce gain at many different wavelengths simultaneously—a key requirement for wavelength division multiplexing (WDM). As for all amplifiers, broad emission cross sections are essential. Er<sup>3+</sup>-doped borate glass has broad emission cross-section. However, the high phonon energy prevents it from application for Er<sup>3+</sup>-doped fibre amplifier.
In this paper, Er<sup>3+</sup>-doped borate glass containing high Ag<sup>+</sup> contents was synthesized and their absorption spectra were measured. The results showed that no metal silver cluster exists in the glass and silver element was equably distributed into the glass as sliver ions. Judd-Ofelt parameters, radiative lifetimes as well as the quantum efficiency were calculated. It is found that introducing high content of Ag<sup>+</sup> into Er<sup>3+</sup> doped borate glass leads to an enhancement of the refractive index and reduces the phonon energy in glass host. As a result, the quantum efficiency and emission cross-sections increase, and the 1.5 μm emission intensity increases. Meanwhile, Er<sup>3+</sup>-doped borate glass containing high content of Ag<sup>+</sup> shows the broad full width at half maximum (FWHM)of about 80 nm.关键词：sliver;judd-ofelt parameters;quantum efficiency;1.5 μm light emission90|141|1更新时间：2020-08-12 - 摘要：Transient voltage-current characteristics of OLED show hysteresis effects in the bias regime depending on the direction and speed of bias sweep. This behaviour was investigated here for the example of device based on the configuration of ITO/CuPc/NPD/Alq<sub>3</sub>/LiF/Al. The existence and relatively long recharging time of p-type deep accepter-like trap on the recharging process after the change of bias of OLED should be responsible for these phenomena. According to the above mentioned analysis, some measurements were taken to change the concentration of those deep traps in order to improve the optical and electric performance of OLED.关键词：OLED;voltage-current characteristic;p-type deep accepter-like trap;forward sweep106|199|0更新时间：2020-08-12
- 摘要：Tremendous progress has been made in the science and technology of organic light-emitting diode in developing flat panel displays. OLED efficiency and lifetime are the primary issues limiting the widespread commercial use. To solve the problem, finding out novel materials and applying new structure are usual methods. The degradation of the interfaces between electrode and organic layer is also an important factor for the stability. Up to now, different treatment both physical and chemical technique has been used to modify the interface, and also, there is a good choice of inserting a nano-layer into the interface. <br>Organic light-emitting diodes inserted LiF film,which usually is used for cathode modifying layer, between anode and organic layer were fabricated by vapor thermal deposition. The structure of the diode is ITO /LiF /TPD(30 nm)/Alq<sub>3</sub>(40 nm)/Al(100 nm) (TPD:N, N'-diphenyl-N, N'-bis(3-methylphenyl )-1,1' -biphenyl-4, 4'-diamine, Alq<sub>3</sub>: tris(8-quinolinolato)- aluminum), and the thicknesses of the LiF film are 0.5,1.0,1.5 and 2.0 nm detected by INFCON XTM/2 deposition monitor. The insertion of the ultra-thin LiF layer between ITO and organic layer improves the photoelectric characteristics of the diodes directly, which blocks the hole injection and improves the efficiency of the diodes. Firstly, the ITO surface is smoothed after depositing a LiF film and that may reduces the formation of non-emissive traps and block the diffusion of In<sup>+</sup> ion from ITO to organic layer. The efficient recombination of holes and electrons in emissive layer improves the luminance and efficiency. Secondly, the LiF buffer layer can blocks hole injection and improves the properties of the diodes, however, a thicker LiF layer can reduce the characteristic of the diodes and it was necessary to optimize the LiF thickness. Finally, it was found that the luminance and efficiency of the diode are maximized when 1.0 nm LiF hole buffer layer is inserted between ITO and TPD.关键词：OLED;LiF buffer layer;hole buffer187|466|1更新时间：2020-08-12
- 摘要：It is a general method to vary emission color by doping dyes in OLED devices. The energy transfer from host to dyes is important process in blend system in OLED devices. In this paper, the spectra of the active layer based on co-polymer poly doped with DCJTB were studied in LEC devices. The structure of the device is ITO/poly∶DCJTB +PEO +LiCF3SO3/Al.The photoluminescence (PL) spectrum of the co-polymer (peak at 550 nm) is almost cover the absorption spectrum of DCJTB completely, it is necessary for energy transfer from co-polymer to DCJTB. When the blend film was exited by the absorption peak of the co-polymer (450 nm), where there is no absorption of DCJTB, the PL spectra exhibit the emission properties of DCJTB mainly, and the electroluminescence (EL) spectra of the LEC device show similar properties as PL spectra. This result showed that the energy transfer between the co-polymer and DCJTB plays important roles in the active layer of LEC device.关键词：energy transfer;LEC device;doping99|135|3更新时间：2020-08-12
- 摘要：Zinc oxide,which is a direct wide band-gap(3.37 eV) compound semiconductor with the large exciton binding energy(60 meV),has recently become a very popular material due to its good photoelectric and piezoelectric properties.Besides, the pulsed laser deposition(PLD) technique has its unique advantages such as high controllability of film composition, the easy control of experimental parameters and an inherently clean process which make it easy to deposit high-quality complex compound films.The dependence of the surface morphology, crystalline quality and photoluminescence property of the ZnO films prepared by pulsed laser deposition on the growth temperature and the dependence of the surface morphology of the samples on the different deposition time were investigated in this paper. The ZnO thin films were fabricated on Si(100) substrates by pulsed laser deposition in temperature ranging from 300 ℃ to 700 ℃ at a oxygen ambient pressure of 16 Pa. The surface morphology, the structural characteristics and the optical property of ZnO thin films were characterized by atomic force microscopy(AFM), X-ray diffraction(XRD) and PL spectra. The two-dimensional images, three-dimensional images and profiles of the samples were analyzed by AFM. The results indicated that the surface roughness of the films increased at first and decreased later, the quality of crystallization is improved gradually and photoluminescence property is also enhanced.It was found that the film grown at 700 ℃ has a much smoother and denser morphology, ideal crystalline quality and better optical properties. Other ZnO thin films were fabricated at an oxygen ambient pressure of 5.7 Pa in the growth time ranging from 10 to 45 min. Using AFM, we understood that it is important to have crystalline grains grown adequately in a sufficient period of time.关键词：ZnO thin film;PLD;AFM;XRD;photoluminescence102|143|1更新时间：2020-08-12
- 摘要：The development of power-LED needs to improve its light extraction efficiency, secondary optical design based on microlens array is a effective way for improving light extraction efficiency. A packaging structure of high-power LED was presented, microlens array was employed in the secondary optical design, optical properties of the package was studied using Trace Pro. The results showed that microlens array technology can significantly improve the optical performance of the LED and increase light extraction efficiency, illumination attenuation of LED can be reduced by more than 12%, the results are satisfactory.关键词：LED;microlens array;optical proporties;packaging121|166|3更新时间：2020-08-12
- 摘要：The Ⅲ-Ⅴ nitrides have been nowadays successfully used as active layer in high-brightness blue and green light emitting diodes (LEDs) and lasers diodes (LDs). It is more essential to know optical properties of the GaN based semiconductor materials such as optical band gap and radiation recombination transition prior to new devices fabrication. Photoluminescence (PL) spectrum is the most common tools to be employed for studying gap states in GaN. A frequent finding is that when GaN films are exposed to super-band gap illumination, a characteristic yellow luminescence band (YLB) is often observed. Many studies have attempted to uncover the origin of the yellow luminescence in GaN films. In this paper, we present an experimental investigation of the selected GaN samples grown by metal organic vapor phase epitaxy (MOVPE), using photoluminescence (PL) spectra excited with different excitation sources. The samples studied here are nominally un-doped GaN of 1 000 nm thick grown on a 10~30 nm AlN epilayer by MOVPE. Prior to the GaN epilayer growth, a 5~10 nm thick AlN buffer layer was grown on <em>c</em>-plane Al<sub>2</sub>O<sub>3</sub> substrate. The PL spectra of the sample are excited separately by using four different excitation light sources. The correlation of the photoluminescence spectra and excitation source of the GaN film grown by metal organic vapor phase epitaxy on sapphire substrates were investigated. By analysis of the PL spectra, it has been found that the yellow luminescence band appears when continuous wave Xe lamp and He-Cd laser sources are used. The central wavelength of wider YLB is located at near 550 nm and the main peak of the band edge emission is observed at 365 nm. The YLB tends to disappear when, He-Cd and YAG pulse wave sources are employed. This phenomenon was attributed to impurity band saturation when the samples were excited by the pulse wave light sources with the high power density. It was concluded that the yellow radiation evidently depends on the excited light source.关键词：GaN film;photoluminescence spectra;pulse light scurce;continuous light scurce109|98|0更新时间：2020-08-12
- 摘要：The luminous flux efficiency of white LED combining blue LED chip and YAG[DK(]∶[DK)]Ce yellow phosphor was calculated theoretically. According to the principle of photometry and considering the modification of the vision function <em>V(λ)</em>, the theoretical limitation of luminous flux efficiency for white LED was calculated from the emission spectrum of the white LED at the condition of the chromaticity coordinate <em>x</em>=0.325, <em>y</em>=0.322, the rendering index 81.5, and the color temperature 5 913 K. The result showed that the luminous flux for LW white LED radiation power output is 298.7 lm and the total photons are 2.7×10<sup>18</sup>. If under ideal conditions, one electron-hole pair injected yields one blue photon and the quantum efficiency of the phosphor equals one, the numbers of electron-hole pair must equal to the numbers of white photons. So LW white LED radiation power output has to consume 1.51 W electric powers and the luminous flux efficiency limitation of electrical to optical conversion for the white LED is 197.8 lm/W at above condition.关键词：white-emitting LED;luminous flux;luminous efficiency166|512|3更新时间：2020-08-12
- 摘要：The sol-gel technique offers the greatest possibility of preparing thin films of large and small areas by controllability of composition and relatively simple facilities. In the sol-gel process, thin ZnO films are obtained through post-depositional crystallisation. As-deposited films must be transferred into a crystalline state from an amorphous state by post-annealing. This paper addresses the effect of annealing temperature on the microstructure and the photoluminescence of ZnO thin films.<br>
2-methoxy ethanol and monoethanolamine were used as the solvent and stabilising agent, respectively. The dopant source for natrium was natrium nitrate. Zinc acetate dihydrate and the source of dopant (10%) were first dissolved in a mixture of 2-methoxy ethanol and monoethanolamine at room temperature. The concentration of zinc acetate was 0.8 mol/L and the molar ratio of monoethanolamine to zinc acetate was kept at 1[DK(]∶[DK)]1. The solution was stirred for 2 hours at 343~353 K to yield a clear, homogeneous and transparent solution using a magnetic stirrer, which served as the coating solution. The coating was made during the two days when the solution was prepared. The substrates were spun at 3 000 r/min for 30 s, while coating. After spin coating the substrates were kept at 623 K for 10 min. To evaporate the solvent and eliminate the organic component in the film. This procedure was repeated ten times. The films were then annealed at 873, 973 and 1 073 K respectively for 90 min.<br>
High quality <em>c</em>-axis Na-doped ZnO films on Si (100) substrates were grown by the sol-gel process. The PL spectra were investigated at room temperature. Photoluminescence spectrum shows a strong ultra violet exciton emission peak at 361 nm, a weak violet exciton emission peak at 388 nm and a blue emissions in the range of 425~435 nm.关键词：microstructure;optical properties;sol-gel method;Na-doped ZnO105|115|0更新时间：2020-08-12 - 摘要：In order to develop solid-state dye laser with high performance, it is a feasible way to embed dyes in porous medium. As a excellent porous medium, the oxidized porous silicon has a multivariate porous structure, a great specific surface area, and stable physics and chemistry property. Rhodamine 6G is a kind of laser material which has the widest gain bandwidth, always to be the first object when the ultrashort pulse laser technology was researched.<br>
In this paper, porous silicon samples were prepared by electrochemical anodic oxidization.After oxidization at high temperature, oxidized porous silicon samples were fabricated.Through the method of marinating, this research regarded oxidized porous silicon embedded by Rh6G as substrate, and formed Rh6G/ oxidized porous silicon composite films, then made a contrast research on fluorescence features of Rh6G in ethanol liquor, oxidized porous silicon and porous silicon. The samples of porous silicon and oxidized porous silicon were detected by fluorescence spectra. Investigation demonstrated that the PL peak of oxidized porous silicon has a blue shift, along with the obvious reduction of
PL intensity, compared with that of porous silicon.It was also found that the transparency of oxidized porous silicon is increased after high temperature oxidation, and its luminescence cant be examined in composite films. So, the oxidized porous silicon is impossible to disturb the fluorescence spectra of Rh6G which had been embedded in pores.Compared with ethanol liquor, the spectral full width at half maximum of Rh6G in oxidized porous silicon is improved slightly, its peak wavelength has a little red shift, and its spectral symmetry is improved greatly. Similar to in ethanol liquor, Rh6G had the single molecules luminescence in oxidized porous silicon. In the oxidized porous silicon, the Rh6G is subjected to a restriction of the nanopores, and exist mainly the form of single molecule.At the same time, it was possible that a small amount of dipolymer and multipolymer of Rh6G was formed in the nanopores. So, the fluorescence spectrum of composite films were determined by the size distribution variation of the oxidized porous silicon and the degree of the Rh6Gs aggregation.<br>
By this experiment, it was found that the oxidized porous silicon perhaps is a good medium in the deve-lopment of solid-state dye lasers.关键词：oxidized porous silicon;anodic oxidization;Rh6G;fluorescence spectra104|104|1更新时间：2020-08-12 - 摘要：Lanthanide-based nanocrystals have shown great potential to be used as luminescent materials but their biological applications have been limited because most of the nanocrystals synthesized so far do not be water soluble or biocompatible. When synthesizing lanthanide (Ⅲ)-doped nanocrystals, organic surfactants are often used as ligands to control the particle growth and to stabilize the particles against aggregation, and therefore the nanocrystals are not water soluble. In this paper, we developed a very straightforward method to prepare water soluble chitosan/LaF<sub>3</sub>∶Eu<sup>3+</sup> nanocomposite particles with functional chemical groups on their surfaces. Chitosan is found to cap the nanocrystals during the synthesis process, which renders them water soluble and biocompatible, and provides functional groups such as hydroxyl and amino groups for further attachment of biomolecules. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) absorption spectra. The results shown that the nanocomposite particles have average size of about 20 nm, the sizes of the nanocrystals were calculated from the XRD pattern based on the Debye-Scherrer formula, assuming that the particles are spherical in shape. Further, we exhibited the excitation and emission spectra of these nanocomposite particles and described the luminescent mechanism corresponding to the transition levels. The chitosan/LaF<sub>3</sub>∶Eu<sup>3+</sup> nanocrystals were well dispersed in water and their fluorescent properties were studied. The results showed that the luminescent intensity corresponding to <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>1</sub> transition of Eu<sup>3+</sup> ions in the Eu<sup>3+</sup>-doped LaF<sub>3</sub> nanoparticles increased remar-kably with increasing the doping concentration of Eu<sup>3+</sup> ions and reached a maximum at approximately 10%. Finally, we introduced the coupled way between the chitosan/LaF<sub>3</sub>∶Eu<sup>3+</sup> nanocomposite particles and the fluorescent protein(FITC). The nanocomposite particles are very suitable for use in biological applications, for example, intracellular labelling or measurements, because they are very small in size. The use of this method can be extended to the synthesis of other water soluble and biocompatible lanthanide(Ⅲ)-doped luminescent nanocrystals.关键词：Eu;chitosan;nanocomposite particles;photoluminescence89|46|2更新时间：2020-08-12
- 摘要：In my paper, the rare earth (Eu, Tb) complexes were synthesized with citric acid as the first ligand and 1,10-phenanthroline (phen) as the secondary ligand, ternary rare earth complexes with a series of different ratios of Eu/Y and Tb/Y were synthesized. The complexes synthesized were characterized by IR spectra, UV spectra and emission-excitation spectra. IR spectra and elemental analysis show that composition and structure of the complexes synthesized is the same as the data in accordance with a chemical formula, the rare earth ions coordinated with the ligands, and the complexes is the target product. From the IR spectrum it can be seen, the C—O bond(1 729 cm<sup>-1</sup>) of citric acid symmetric stretching vibration, C—O bond (1 217 cm<sup>-1</sup>) symmetric stretching and O—H hydrogenous bond formation of hydroxyl plane bending vibration (945 cm<sup>-1</sup>) disappeared after the formation of complexes. The absorption of the ligand (phen) resulted in the complexe’s absorption which holded the character of π→π<sup>*</sup> transition with the formation of the ligand (phen) having little effect on the transition. Y<sup>3+</sup> does not produce fluorescence itself, but the fluorescence intensity of the europium(Ⅲ) complexes increased with yttrium(Ⅲ) doped. The energy of ligand triplet state was transfered to yttrium(Ⅲ) difficultly because of the high excitation energy and f<sup>0</sup> structure of yttrium(Ⅲ), so that europium(Ⅲ) can get more energy, and its fluorescence intensity increased, which is so-called the co-luminescence.关键词：rare earth complexes;doping;citric acid;benzoic acid;1;10-phenanthroline118|233|1更新时间：2020-08-12
- 摘要：Six new ternary complexes of terbium were synthesized with benzoic acid or its derivatives as the first ligand and succinic acid as the second ligand under the condition of non-aqueous solution. The structure and composition of the title complexes were characterized by means of elemental analysis, EDTA titrimetric method, UV spectra and IR spectra. The fluorescence properties and thermal stability of the title complexes were also studied. The results show that the induction of succinic acid can greatly increase the ability of the first lignd transfering light energy to the central terbium ion. The sequence of energy transmission is as follows:p-chlorobenzoic acid >m-chlorobenzoic acid> anisic acid＞p-toluic acid＞benzoic acid＞p-hydroxylbenzoic acid. The title complexes have much higher luminescence intensity than their corresponding binary complexes.关键词：terbium;complex;photoluminescence83|102|2更新时间：2020-08-12
- 摘要：Five complexes of dysprosium were synthesized, in which benzoic acid or halobenzoic acids were as the first ligand, and nitrogen-heterocyclic (phenanthroline or 2,2'-dipyridine) as the second ligand. By elemental analysis, rare earth coordination titration, the compositions of the complexes were confirmed to be Dy(BA)<sub>3</sub>(bpy), Dy(BA)<sub></sub>3(phen), Dy(ClBA)<sub>3</sub>(phen)(EtOH), Dy(BrBA)<sub>3</sub>(phen)(EtOH) and Dy(IBA)<sub></sub>3(phen)(EtOH),(BA=benzoic acid, ClBA=p-Cl-benzoic acid, BrBA=p-Br-benzoic acid, IBA=p-I-benzoic acid, bpy=2,2'-dipyridine, phen=1,10-phenanthroline), respectively. The ligands and coordination compounds were studied by means of IR spectra, UV-spectra, fluorescence excitation and emission spectra. The results showed that benzoic acid or halobenzoic acid is bonded with Dy(Ⅲ) through oxygen atoms in the carboxyl group, and phen or bpy ligands is bonded to Dy(Ⅲ) through nitrogen atoms. Fluore-scence emission spectra indicated that the fluorescence emission intensity of Dy(ClBA)<sub>3</sub>(phen)(EtOH) is the strongest, Dy(BrBA)<sub>3</sub>(phen)(EtOH) is second, and Dy(IBA)<sub>3</sub>(phen)(EtOH) is the weakest among the Dy(Ⅲ) with halobenzoic acid and phen complexes. The intensity of Dy(BA)<sub>3</sub>(bpy) is little stronger than Dy(BA)<sub>3</sub>(phen) at about 481 nm, but at about 573 nm, Dy(BA)<sub>3</sub>(phen) is more stronger.<p/>
The <sup>4</sup>F<sub>9/2</sub> energy of Dy<sup>3+</sup> ion is 20 509 cm<sup>-1</sup>, the triplet energy of phen is higher than the excitation energy of Dy<sup>3+</sup> ion, thus the absorbing energy of phen can effectively transferred to Dy<sup>3+</sup> ion, and producing a characteristic spectrum. The fluorescence intensity of Dy(ClBA)<sub>3</sub>(phen)(EtOH) is the strongest among the three halobenzoic acid complexes, it shows that the triplet state energy of p-Cl-benzoic acid matches well with the lowest excitation energy of Dy<sup>3+</sup> ion.90|98|0更新时间：2020-08-12 - 摘要：The holographic recording in four azo dye-doped poly(methyl methacrylate) (PMMA) films were studied by a special optical path in this paper, the results indicated that the diffractive efficiency of DMTAA can be up to 22%, and DMTAA is an ideal holographic recording material. Furthermore, we discussed and analyzed the principle for the real time and permanent holographic storage of azo dyes in this thesis.关键词：holographic recording;azo dyes;four-wave mixing105|368|1更新时间：2020-08-12
- 摘要：The field emission display have been recognized as the one of the most promising electron field emitters since the first field emission experiment reported in 1995. CNTs as emitters in the field emission display devices have been demonstrated during the last decade years. Now, the field emission display methods of carbon nanotube include triode structure and diode structure. The diode structure display consists of the anode and the cathode.It needs high drive voltage and wide modulating voltage scope which cost a lot. So, a triode structure was designed by studying the flat grid structure. In addition to the anode and the cathode, the triode structure display contains grid electrode which offers a guarantee to the safe field emission operation. Furthermore, the turned on voltage of the field emission is depressed and the scope of modulating voltage is minished compared to the diode structure. Experiment indicated that the vision brightness can be controlled and grid modulating circuit can be protected by adjusting anode voltage, the grid voltage and modulating voltage scope of field emission can be minished further after the grid is aged and it can also be minished by increasing anode voltage and shortening the distance between cathode and anode. The results will provide helpful information for further research of field emission display.关键词：carbon nanotube;field emission;modulating voltage;flat grid structure95|181|4更新时间：2020-08-12
- 摘要：Since the application of liquid crystal begun in 1960s, the related manufacturing technology has already been considerably mature, but there are still many problems to desiderate to be resolved. The charge-accumulation of TN-LCD is the one of quite intractable problems in producing of LCD. Because quantitative measurement of charge-accumulation is hard to be done, the problem is still up in the air. Here the charge accumulation of LCD was analyzed from the opinion of the dielectric physics in this paper, and it was found that the accumulated charge can be produced in the interface when the ratio of dielectric constant and conductivity for alignment layer doesnt equal to that of LCD layer. The larger the ratio of dielectric constant and conductivity, the higher charge accumulation, and if the ratio of dielectric constant and conductivity equals to each other, there is no charge to be accumulated, this will be helpful to solve the problems such as image sticking, slow response <em>etc</em>.关键词：LCD;charge accumulation;dielectric constant133|386|2更新时间：2020-08-12
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