最新刊期
卷 28 ， 期 3 ， 2007
- 摘要：White light-emitting diode(LED)is rapidly evolving for use in the special and general illumination applications. A main method for producing white LED is to utilize a InGaN blue or near UV LED chip and phosphors which have the characteristic of wavelength-conversion.The essentials of phosphors which are sui-table for white LED include: (1)phosphors are efficiently excited by blue or NUV LED and efficient radiative emission of appropriate visible wavelength; (2)excellent preformence of temperature quenching; (3)good stability and (4)small particle size(≤5nm). In this paper, the schemes and principles on advanced phosphors for white LED are discussed in great detail. It is important that a relationship between the 5d centroid shift in Eu2+ and Ce3+ ions, anion polarizability, covalency, electronegativity of the cations, perturbations of the crystalline environment in phosphor hosts, as P.Dorents's results. Based on our studies, luminescence properties and energy transfer of Ce3+,Pr3+,Tb3+,Eu3+,Eu2+ and Mn2+ ions are presented in the (Y,Gd)3(Al,Ga)5O12 garnet and Ca8A(SiO4)4Cl2 (A=Mg,Zn)chlorosilicate systems and some tungstate and molybdate. The staircase spectrum in Eu2+4f6(7FJ)5d configuration was observed in chlrosilicate phosphors at RT. The purish-blue(Ce3+), green(Eu2+,Mn2+) and red(Eu3+)emission bands arise from Ce3+,Eu2+,Mn2+ ions locating at eight-, six-and four-coordinated inequivalent sites in chlorosilicate, respectively. White LEDs which show the related color temperature in the range of 2700~8000K and high rending index (Ra) are obtained by combining InGaN blue chip and phosphors. The emission spectrum, chromaticity coordinate (x,y),luminous flux and luminous efficiency of white LED packaged by us were reported. The optic characteristic changes at various forward-bias currents(IF)have been discussed. In this study, it was shown that chromaticity coordinate values (x and y) of white LED shifted and resulted in the related color temperature (Tc) increase. The Tc change and stability on a white LED can been characterized by a difference valure (ρTc) of related color temperature at various IF. High power and high brightness white LED is the future of solid state lighting. New efficient phosphors for SSL will be developed.关键词：phosphor;white LED;luminescence;solid state lighting;rare earth activators198|182|24更新时间：2020-08-11
- 摘要：The influence of driving field phase fluctuation on lasing without population inversion in a three-level cascade system was studied. In the rotating wave and slowly varying envelope approximations, the density-matrix motion equations for the three-level cascade system, considered the influence of driving-field phase diffusion is solved, and the exact linear analytical solutions of the three-level cascade system with the driving field having the phase fluctuation in the steady state are obtained. The dependence of LWI gain, dispersion and the populations on the probe field detuning and the strengths of coherent pumping, respectively, are examined and simulated numerically. It was shown from the results of numerical calculation about the steady-state solutions of three-level cascade system that the gain of lasing without population inversion will be decreased due to driving-field phase-fluctuation. The effect can be compensated by increased driving-field intensities. However, the effect that LWI gain is decreased due to driving-field phase-fluctuation can not be always compensated by increased driving field Rabi frequency. Lasing without population inversion is still obtained even if the linewidth due to driving-field phase-fluctuation is large enough. The pre-sence of the linewidth prevents the cascade system from obtaining a high refractive index along with zero absorption. The cascade system can still exhibit a larger refractive index and zero absorption at the lesser linewidth. The linewidth tends to destroy lasing without population inversion and refractive index enhancement. There is no population inversion for the lasing transition and for the driving transition under the given condition. And the condition without population inversion has nothing to do with the variety of linewidth in the steady-state analytical solutions. That is to say, there is not possibility for the cascade system that a change from lasing with population inversion to lasing without population inversion can occur with the linewidth increasing or with the Rabi frequency of driving-field increasing. The conclusion is very different from that obtained in other inversionless lasing system.关键词：atomic coherence;lasing without inversion;phase diffusion;cascade system112|130|2更新时间：2020-08-11
- 摘要：The influence of electric field on properties of strong-coupling magnetopolaron in quantum well was investigated using linear-combination operator and unitary transformation method. The ground state energy and vibration frequency of magnetopolaron were obtained. The effects of well-width L, electric field strength F and the cyclotron frequency ωc of magnetic field on the ground state energy were discussed. The relations of the ground state energy of the magnetopolaron with the coupling constant, the well-width and the electric field strength are derived. Numerical calculations illustrated that the absolute value of the ground state energy of the strong-coupling magnetopolaron will decrease with increasing the well-width and increase with increasing the external electric field strength. The absolute value of the ground state energy of the strong-coupling magnetopolaron will rise with increasing the cyclotron fre-quency. The smaller well-wider and the larger is the absolute value of the ground state energy of the magnetopolaron, the peculiar quantum size effect is significant.关键词：linear combination operator;magnetopolaron;quantum-well;electric field125|186|1更新时间：2020-08-11
- 摘要：Spontaneous emission rate is not only affected by the properties of the material itself, but also depends on the dielectric properties of the surrounding media. Recently, some work has been carried out to study the dependence of spontaneous emission rates of the luminescent-ion-containing nanometer particles on the refractive index of the media. Based on the free distribution of nanometer particles in media, the pro-bability density of luminescent lifetime is analyzed. Since nanometer particles distribute freely in media, the number of nanometer particles in a given volume surrounding the luminescent center obeys the Poission distribution. The local relative refractive index nr, which is the ratio of media effective refractive index to particle refractive index, is affected by the particle number of nanoparticles within a sphere of radius half of the radiative wavelength. The probability density function of nr can be obtained according to the dependence of nr on the particle number. Based on the relation between nr and luminescence lifetime, the analytical form of probability density function of lifetime is obtained. A calculation has been done based on the parameters given in Meltzer's experiment (Eu3+ doped Y2O3 in methanol). The result shows that the relative fluctuation of luminescence lifetime is too small to be observed. However, with increasing size of nanometer particles or density of nanometer particles, the relative fluctuation of lifetime increases greatly and could be observed.关键词：nanometer particle;luminescent lifetime;local-field effect;refractive index;mean square deviation110|102|0更新时间：2020-08-11
- 摘要：A negative-donor center (D-) in a semiconductor heterostructure or quantum well is formed by a neutral center (D0) trapping an extra electron. This system has attracted considerable attention since the early days of quantum mechanics. D- centers are one of the simplest many-body electronic systems which can be used as a test for theoretical descriptions of e-e correlation. In previous experimental and theoretical studies, the dependence of the binding energy of D- on the magnetic-field strength and on the dimension of the quantum well have been investigated. Although there have been great efforts toward understanding the behavior of the D- centers in Q2D systems, very little information is available concerning polaron effects on the properties of the D-center in a parabolic quantum well(PQW). The polarization potential and the binding energy of the D- center in a parabolic quantum well are inves-tigated. The study has taken the effect of bulk longitudinal optical (LO) phonons into account. In order to simplify the calculation, we use the simple trial function for both electrons. By using the method of modified Lee-Low-Pines(LLP) variational method, the polarization potential and the ground state energy of D- center in the GaAs/AlxGa1-xAs PQW are obtained. The contribution of the impurity and LO phonon interaction to the total electron energy can be eliminated by the first canonical transformation, and the effect of this displacement on the lattice polarization leads to the polarization potential which partially compensates the electron-impurity Coulomb interaction. By the second canonical transformation, the ground state energy of the D- center in the infinite parabolic quantum well is worked out, and then the binding energy of D- center can be gained by further calculations. The research results indicate that, the ground state energy and binding energy of the D- center decreases rapidly with increasing L at the beginning, then decreases very slowly with increasing L and finally closes to the three-dimensional value in GaAs. Polaron effects on the properties of the D- center in a PQW were found to be important. Because the binding energy of the D- center is much smaller than that of a shallow donor, the relative contribution of the polaron correction is larger.关键词：parabolic quantum well;polaron;D- center121|135|0更新时间：2020-08-11
- 摘要：In recent years, many works have been devoted to the study of the mesoscopic systems, because the electronic transport property in mesoscopic systems is not only a basic theoretical topic but also could benefit the design of useful electronic devices. Research on these systems revealed many novel phenomena. These phenomena, which usually appear in mesoscopic systems, are called mesoscopic phenomena. One of the mesoscopic phenomena is the persistent current flowing in a mesoscopic ring threaded by a magnetic flux. Experimental and theoretical research has shown that a magnetic flux which threads an isolated ring of mesoscopic dimensions creates persistent current. Moreover, it has been theoretically shown that in such a system self-sustaining current can still run even if the external flux is switched off. General quantum-mechanical principles require that the wave functions, eigenvalues, and hence all observable quantities should be periodic in the magnetic flux threading the loop with a period 0(0=hc/e being the flux quantum). It is well known that the magnetic flux destroys the time-reversal symmetry and, as a consequence, the degeneracy of the states carrying current clockwise and anticlockwise is lifted. Since the discovery of the persistent current, there have been many studies on the single ring, coupled ring, and multiple-arm ring structures. Studies show us that in the presence of a transport current, the persistent current can flow in a ring, even in the absence of a magnetic field. The purpose of this paper is to study persistent currents in the triple-arm ring coupled to two external leads by quantum waveguide theory. It is found that in the presence of a transport current, the persistent currents can flow in a triple-arm ring, even if the magnetic flux is absent and the lengths of the upper and the lower arms are equal. With different lengths of the three arms, the persistent currents in the three arms are different. Beside, the persistent currents in the triple-arm ring and the single ring are different, even though the ratios of the upper arm to the lower arm of the two rings are the same.关键词：quantum waveguide theory;mesoscopic structure;persistent currents103|103|0更新时间：2020-08-11
- 摘要：Photonic crystal is regarded as the counterpart of the electronic crystal in the field of optics, many concepts of the solid state physics are introduced into the photonic crystal, such as reciprocal lattice vector, Brillouin zone and energy band structure, etc. People can understand the operating principle of photonic crystal through researching electronic crystal. Back in the seventies of the 20th century, with the gradual minia-turization of semiconductor devices, the concepts of quantum well and superlattice were introduced in semiconductor materials. People are excited to make photon quantum well and superlattice through imitating the semiconductor quantum well because of the numerous similarities between the photonic crystal and the semicon-ductor, much progress has been made both in experiment and in theory, quantum well structures are realized in one-dimension, two-dimension and three-dimension photonic crystal, the phenomenon of optical quantum well similar to semiconductor quantum well is observed, the quantized photon levels emerge from the transmission spectrum. The observable information of optical spectrum includes frequency and intensity. Traditionally, restricted by the complexity of the spectral intensity and the precision of data processing, the majority research of the spectrum is concentrated on frequency. With the improvement of the experiment condition and the continuous optimization of algorithm as well as the advancement of the calculation conditions, the research on spectrum intensity is becoming more and more important. In order to gain the accurate spectral intensity absolute value, people are always searching for a simple detection method which can reflect the spectrum structure truthfully. Essentially, the calculation of the spectrum intensity is a problem of quantum mechanics. Although the quantum mechanics describes the existence of the microscopic material by the expression of probability, according to the Einstein light quantum supposition, we can also research the light wave by decompounding it into single photon. The light wave is the macroscopic ensemble average of the photon particles, while photon is the micro-quantization of the light wave. In the photon quantum well structure, the spectrum intensity is proportion to the number of the photons which tunnel through the photonic wells. The larger the number is, the stronger the tunneling spectrum intensity is; the more concentrated the light beam is, the higher the efficiency is. It is more suitable to produce the laser source, photoelectric detector, optical switch and many other optical communication devices. The relative studies are more tempting and have great application prospect. The quantized energy states of photonic crystal quantum-well are discussed by finite-difference time-domain method(FDTD). The results show that for the closed photonic quantum-well the number of resonant transmission peaks is equal to that of open quantum-well's, the positions are almost unchanging, but for the closed photonic quantum-well, its extractive light intensity is obviously stronger, the transmissivity is higher, the frequency selectivity is better and the quality factor Q is higher. Simultaneously the optical field distributions in both quantum-well structures are obtained, it is shown that the open quantum-wells are traveling-wave wells while the close quantum-wells are standing-wave wells, which has firmly confirmed the proposal that closed photonic quantum-wells could bound optical field better, the physical mechanics which results in these conclusions are discussed. The research in this area is rarely seen.关键词：closed quantum wells;open quantum wells;resonant tunneling;transmission spectra;photonic band gap118|116|0更新时间：2020-08-11
- 摘要：With the development of several experimental techniques,for instance, metalorganic chemical vapour deposition, molecular beam epitaxy and electron beam lithography combined with reverse mesa etching, there has been of considerable interest in understanding of hydrogenic-impurity states in low-dimensional semiconductor heterostructures such as quantum wells, quantum wires and quantum dots. In recent years, there has been great interest in investigating quantum dots both theoretically and experimentally. Due to the small structures of QD's, some physical properties such as optical and electron transport characteristic are quite different from those of the bulk materials. The study of the impurity states in these low dimensional strictures is an important aspect to which many theoretical and experimental works based. Recent investigations in the reduced dimensionality show that the impurity binding energy will be enhanced with the deduction of the dimensionality. In recent years, the problem of a bound magnetopolaron in a quantum dot has been extensively studied. Au-Yeung et al. studied the combined effects of a parabolic potential and a Coulomb impurity on the cyclotron resonance of a three-dimensional bound magnetopolaron by using Larsen's perturbation method. Chen et al. investigated thickness effecting on energy levels of impurity-bound magnetopolaron in a parabolic quantum dot by the second-order perturbation theory. Khamkhami et al. studied properties of the magneto-bound polaron in CdSe spherical quantum dots in the framework of the effective mass approximation using the strong coupling method (Landau-Pekar approach). Charrour et al. presented a systematic study of the ground state binding energy of a hydrogenic impurity in cylindrical quantum dot subjected to an external strong magnetic field and performed calculations within the effective-mass approximation using the variational procedure and considering an infinite confining potential on all surfaces of the system. Nguyen et al. analyzed magnetic field effects of parabolic confining potentials on the binding energy of hydrogen impurities in quantum dots using a very simple trial function with only one variational parameter. Chen et al. derived ground state properties of the bound magnetopolaron using the linear combination operator and unitary transformation method. One of this paper's authors by using the linear combination operator and unitary transformation methods achieved the vibration frequency and the average number of phonons of the strong-coupling bound magnetopolaron in a parabolic quantum dot. By using the variational method of Pekar type, we have studied both the ground state and the excited state of strong coupling bound magnetopolaron in parabolic quantum dot. The results show that,with the increasing the effective confinement strength,the ground state energy,the average number of virtual phonons around the electron and the resonance frequency of bound magnetopolaron in parabolic quantum dots are decreased. The ground state energy of bound magnetopolaron in parabolic quantum dots increases with increasing the cyclotron frequency of the quantum dots and decrease with increasing the coulomb potential.关键词：parabolic quantum dot;strong coupling;bound magnetopolaron;effective confinement strength101|110|0更新时间：2020-08-11
- 摘要：The quantum information is a new interdisciplinary science in the 21st century, and it has become a research field which attracts strongly much attention in the world. Recently, the study of the quantum computer is in the ascendant. In the process of finding a scheme for quantum computation, quantum chaos aroused much attention. It has been shown that it is possible to induce quantum chaos when running quantum computer and consequently it may destroy the operational condition of the quantum computer. The relationship between quantum entanglement and quantum chaos has already been investigated, and the spin squeezing is regarded as another classical quantum property indeed, then is there a natural relationship between quantum chaos and spin squeezing? In this paper a very typical QKT model in the quantum chaos has been discussed,and the properties of spin squeezing in the quantum chaotic system has been studied. The relation between spin squeezing parameters and chaotic parameter in the two different definitions is worked out by numerical calculation. The stronger that the regular regions are than chaotic ones, which are chosen firstly, in the classical phase space, the stronger the spin system which the initial states locate at the centre of elliptical regions as a result. If the initial states are chosen another condition, the contrary result is obtained naturally. It indicates the spin squeezing is very sensitive to the classical chaos and the classical chaos suppresses the spin squeezing. It is interesting that the definition by Wineland is more sensitive than the one by Kitagawa and Ueda, consequently a conclusion, which the quantum chaos can be described by spin squeezing, is acquired.关键词：quantum chaos;spin squeezing;chaotic parameter103|142|0更新时间：2020-08-11
- 摘要：Organic light-emitting devices (OLEDs) have drawn a large amount of attention due to their potential to be the next generation flat-panel displays instead of current widely using liquid crystal displays (LCDs) since Tang and VanSlyke succeeded in fabricating a high efficient green light emissive OLED driven by low direct bias voltage. The mechanism for electroluminescent (EL) phenomenon involves in the injection of holes from anode and electrons from cathode under forward bias voltage, then the hole-electrons form excitons, and light emission appears through the radiative recombination of excitons. Multilayer organic light-emitting diode with the structure of indium tin oxide (ITO)/N,N′-bis(naphthalen-1-y)-N,N′-bis(phenyl)benzidine (NPB)/aluminum(Ⅲ)bis(2-methyl-8-quinolinato)-4-phenylphenolate(BAlq)/NPB(0~18nm)/tri-(8-hydroxyquinoline)-aluminum (Alq3)/Mg:Ag has been fabricated by changing the film thickness of p-type semiconductor NPB material near to Alq33 layer.111|134|0更新时间：2020-08-11
- 摘要：An oxygen sensing material using tetramethoxysilane (TEOS) and n-octyltriethoxysilane (Octyl-triEOS) as precursors and doped with bis(2,2-bipyridine)(dipyrido[3,3-a 2,3-c]phenazine-N4N5)ruthenium(Ⅱ) (Ru-Dppz) was prepared by the sol-gel method. The fluorescent behaviors of the complex in ethanol and xerogel were investigated. As a result, the emission band of the composite material attributed to the transition from the metal-to-ligand charge transfer (MLCT) shows blue shift compared with that in ethanol. The lifetime of the complex in xerogel was increased compared with that of the pure solid complex. The sensing material with Ru-Dppz as indicator demonstrated good Stern-Volmer plot,high sensitivity, fast response time and long-term stability. The sensitivity was improved using an organically modified silicate (ormosil) as a matrix.关键词：oxygen sensing;ormosil;xerogel;ruthenium complex134|126|0更新时间：2020-08-11
- 摘要：Great interest has been shown in the physics and applications of Fabry-Perot optical microcavity. The spontaneous emission properties of a light emitting material, such as spectrum shape and emission distribution, can be tailored in optical microcavities that have dimensions comparable to an optical wavelength. Up to now, many applications with one-dimensional microcavity structures have been reported, such as resonant light-emitting diodes, vertical-cavity surface emitting lasers and microcavity organic light-emitting diodes (OLEDs). Microcavity OLEDs have shown abilities to reduce the emission bandwidth, improve the color purity, and increase luminous efficiency as compared to those of normal OLEDs. Coupled optical microcavity (CMC) is a structure consists of two or more planar Fabry-Perot microcavities that are coupled to each other. Lately, CMCs have been investigated to show very different emission characte-ristics compared with a single Fabry-Perot microcavity, which presents many potential applications, for instance highly selective wavelength filters, bistable devices, a range of optical and electro-optic switches. In this paper, spontaneous emission properties of a coupled optical microcavity based on an organic light emitting material have been studied under optical excitation for the first time. The structure of the CMC is glass/DBRA/filler/DBRB/tris(8-quinolinolato) aluminium (Alq3)/DBRC. The bottom cavity and top cavity were formed by DBRA/filler/DBRB and DBRB/Alq3/DBRC, respectively. Compared with a broadband spectrum of Alq3 film centered at 511nm, spectral narrowing and intensity enhancement at the two cavity modes 518, 553nm was observed in CMC. The results indicate that CMC structure can strongly modifies the spontaneous emission properties of organic material. The CMC structure may be used as an efficient approach of improving luminous efficiency and can be used to develop potential new type organic photoelectric devices.关键词：luminescence;coupled optical microcavity;organic light emitting;photoluminescence123|122|3更新时间：2020-08-11
- 摘要：Upconversion Tm3+-doped fibre lasers have recently attracted much interest as compact and efficient blue light source. A CW room temperature upconversion laser at 480nm has been demonstrated. Since the high power laser with several hundreds milliwatts to several watts power at 980nm is commercially avai-lable and Yb3+ ion has a large absorption cross-section around 980nm, the Tm3+, Ho3+, Er3+, and Pr3+ ions have successively been excited via the energy-transfer processes in different host by exploiting the Yb3+ ions as sensitizers for the upconversion processes. On the other hand, the transition 3F4→ 3H6 of Tm3+ at 1.8μm has applications in medicine and remote sensing, and consequently it has attracted a lot attention recently. In this paper, the visible and near infrared spectroscopic properties of Tm3+-Yb3+-codoped tellurite glasses and fibres under the excitation of a 980nm laser diode were investigated. Intense upconversion emissions at 480 and 800nm, and weak emission at 650nm, attributed to 1G4→3H6, 3H4→ 3H6, and 1G4→3F4 transitions of Tm3+, respectively, were recorded in Tm3+-Yb3+-codoped tellurite glasses at room temperature. The near infrared emissions at 1020 and 1810nm, which were attributed to transitions Yb3+:2F5/2→2F7/2 and Tm3+:3F4→3H6, respectively, were also observed. The emission characteristics dependence on Tm3+ and Yb3+ ions concentrations was also studied. In addition, intense upconversion emissions at 495 and 830nm, and weak emission at 650, and near infrared emissions at 1060, 1470 and ~1910nm were recorded in Tm3+-Yb3+-codoped tellurite fibres using 980nm laser excitation. The luminescence mechanisms are discussed in detail for designing upconverted blue fibre laser, S-band fibre amplifier, and 1.9μm fibre laser for their potential application in clinical diagnosis and remote sensing.关键词：upconversion;tellurite glasses and fibres;infrared spectroscopy;Tm3+-Yb3+-codoping115|185|0更新时间：2020-08-11
- 摘要：A series of niobic tellurite glasses of 85TeO2-(15-x) Nb2O5-xB2O3-1%Er2O3 (TNBx=0,3,6,9,12,15,molar fraction) glasses were prepared. The effect of B2O3 content on the spectroscopic properties and thermal stability of Er3+-doped niobic tellurite glasses were investigated and discussed based on Judd-Ofelt(J-O) and McCumber theory. For the glasses with different B2O3 content,it is found that the transition temperature (Tg), crystallization onset temperature (Tx)ΔT, J-O intensity parameters Ωt (t=2, 4, 6), the product of fluorescence full width at half maximum (FWHM) and the peak of stimulated emission cross-section (σpeake) reach the maximum values when B2O3 is 9%(molar fraction). The measured lifetime of Er3+:4I13/2 level (τm) increases monotonically with increasing B2O3.The results indicate that in Er3+-doped niobic tellurite glasses, proper amount of B2O3 can be used as a mo-difier to improve thermal stability and spectroscopic properties of Er3+ ions.关键词：niobic tellurite glasses;thermal stability;Judd-Ofelt theory;spectroscopic properties113|70|0更新时间：2020-08-11
- 摘要：KGd(WO4)2 laser crystal is a new laser substance material developed upon CaWO4 crystal. Regardless operated in freedom, under control of Q value or LD pumping, it shows high efficiency. It has good mechanism and optics behave, and can be high-doped.It has potential in non-linearity and Raman scatter area. So the crystal supposes to be premising substance in the field of medical treatment, communication, electronics, remote sensing, industry and so on. Yb ion doping into this kind crystal can be used as femto-second laser material.Now it gets many attention and became a research hotspot. The absorption spectra and fluorescent spectra of Yb3+:KGW laser crystal were measured. From the absorption spectrum of Yb3+:KGW at room temperature, absorption peaks were found in the range from 900 to 1050nm, with three main peaks, 982,954 and 936nm. The 982nm peak is the strongest absorption peak, which can match the emission wavelength of InGaAs LD. It means this kind crystal is suitable for LD pumping. Form the fluorescent spectrum,four fluorescent peaks, 982,998,1017 and 1036nm were found. The 982nm is the strongest fluorescent peak but also strongest absorption peak, so the laser emission in this wavelength can't be realized but the wavelength of 1017 and 1 036nm can do it. Form the absorption and fluorescent spectrum,the value of stark energy spit was make out, with 10 682,10 471, 10 188cm-1 in up-level and 535,358,163,0cm-1 in the down-level. Using Reciprocity method,the absorption cross-section,emission cross-section and fluorescent lifetime were calculated. The absorption cross-section is large,with the value of 1.437×10-19 cm2,this means Yb3+:KGW is good for the absorption of pumping light.The value of emission cross-section is 2.444×10-18cm2, and it can used for laser emission.This crystal has longer fluorescent lifetime of 0.306ms,benefit for energy storage. Because KGW is double-axis crystal, has different character in each direction. The paper emphasize on the influence of this identity to its spectrum behave, take it suit for LD puming into account. The infection of palarization direction and incidence direction of pumping light to crystal fluorescent spectra were measured,it may be theory basis for design LD pumping solid laser. It was found that every state is different.So when LD pumping such laser crystal was designed, the incidence and polarization direction should be taken into account. The influence of the incidence direction seems stronger than that of the polarization direction. The fluorescent intension with different incidence direction is Ic>Ib>Ia and INp>INg>INm. When light incidence is in c axis and the polarization is parallel b axis, the flurescent intension is the strongest.关键词：KGd(WO4)2;emission cross-section;polarization characteristic99|121|1更新时间：2020-08-11
- 摘要：The most efficient phosphors currently available for fluorescent lamps, cathode-ray tubes, and flat panel displays are sulfides. Recently, there is growing interest in developing thin film oxide phosphors doped with transition metal or rare earth ions because they are chemically and thermally more stable. In addition, it is well known that thin film phosphors have advantages such as high contrast ratio, high ambient visibility, high image resolution and good heat resistance in display applications. For these reasons oxide-based thin film phosphors have been widely studied.In this paper, thin films of barium aluminate (BaAl2O4) doped separately with thulium, terbium, and europium were deposited by a spray pyrolysis method. The effects of preparation conditions on the structural and luminescence properties of the films were investigated. Polycrystalline BaAl2O4 films were formed at an annealing temperature above 700℃. Tm3+ and Tb3+ doped films deposited on glass emitted blue and green light, respectively. While in the films doped with europium, both red emission lines from Eu3+ and a broad blue or blue-green emission band from Eu2+ were observed. The BaAl2O4: Tm3+ film has the main emission wavelength at 462nm, and the highest cathodoluminescence (CL) luminance and efficiency at 5kV and 57μA/cm2 were 25cd/m2 and 0.11lm/W, respectively. For the BaAl2O4: Tb3+ film with the main wavelength at 549nm, the highest CL luminance and efficiency at the same condition were 120cd/cm2 and 0.55 lm/W, respectively. A luminance of 50cd/m2 and efficiency of 0.23lm/W were obtained for red emission at 616nm of the BaAl2O4: Eu3+ film grown on glass. Bright blue emission peaking at 452nm was obtained in the BaAl2O4: Eu2+ film grown on an aluminosilicate ceramic plate and annealed in N2:H2 (95:5) at 1100℃. Its luminance and efficiency were 640cd/m2 and 2.93lm/W, respectively.关键词：spray pyrolysis;cathodoluminescence;luminance and efficiency130|94|0更新时间：2020-08-11
- 摘要：Rare earth doped nanocrystalline ZrO2 have attracted great interest. For zirconium oxide has a low phonon energy of about 470 cm-1 and a high refractive index of about 2.1 and is chemically and thermally stable. And rare earth ions, especially erbium, have played an important role in the development of optical communication technology during the past few decades. Recently, erbium doped luminescent materials have received considerable attention for its luminescence and frequency upconversion of infrared radiation into the visible region. The nanocrystalline ZrO2:Er3+ powders with room temperature sharp characteristic emissions were prepared by co-precipitation method. The main work concerns the structures, the luminescence emissions and upconversion emissions change of nanoparticles with the sintering temperature. For ZrO2 sintered at 600℃ the spectra is dominated by the peaks centered at 30.28° (101)t characteristic of the tetragonal structure. For ZrO2 sintered at 800℃ the spectra is dominated by the peaks centered at 28.35°(-1,1,1)m and 31.65°(1,1,1)m characteristic of the monoclinic structure, but there also exist the tetragonal structure. The tetragonal structure almost totally converts to the monoclinic structure for ZrO2 sintered at 950℃. The luminescence emissions contain the blue emission and the green emission. The intensity of the blue emission is greater than that of the green emission. There exist two emission centers of Er3+ in different crystalline phases. One is monoclinic phase, and the other is tetragonal phase. We also find that the emission intensity reaches the maximum value when the ratio of the tetragonal phase to the monoclinic phase comes to a certain value. The room temperature upconversion emission of these samples is also observed and the upconversion emission mechanism is given. We find that the quadratic dependence of the green emissions on excitation power indicates that a two-photon absorption process occurs under 976nm excitation. The effect of the doped concentration of Er3+on the fluorescence emission intensity has been discussed, and the concentration quenching will occur when the concentration of Er3+ is more than 0.9% (atomic fraction) Er3+.关键词：photoluminescence;doping;nanocrystalline ZrO2：Er3+;upconversion107|82|0更新时间：2020-08-11
- 摘要：Rare earth oxide is widely used in X-ray imaging and cathode-ray imaging technology. In experiment, it is found that co-doped ions, such as Li+, Mg2+, Al3+, with luminescence center Eu3+, could increase the light yield of rare earth oxide. However the mechanism for this effect is still under debates. It is well known that the co-doped ions may have the flux effect, which will have an influence on the size of the particle. But other mechanism may coexist to enhance the light output of the material. Based on molecular dynamics and density functional simulation (ADF2005), the defect forming mechanism associated with co-doped ions and its influence on light emission yield of rare earth oxide luminescent material were studied. The results show that the co-doped ions (Li+, Mg2+, Al3+) tend to form interstitial pairs around C2 site in rare earth oxide (Y2O3, Gd2O3), and caused the increase of Y(Gd)—O bond length of host lattice. This factor leads to the decrease of phonon energy and non-radiation transition rate for the rare earth oxide, thus causesd the increase of host's quantum efficiency and light emission yield of luminescence center Eu3+doped into the host material. With the extension of Y(Gd)—O bonds, the deformed host lattice also causes the band gap of the material narrower and the small red shift of HL peaks in the excitation spectrum. However, limited by the simulation power of our computer system and the methods we adopted, our results here can only give qualitative explain to the experimental results. In case of X-ray excitation, smaller band gap will leads to more electron-hole pairs producing in the excitation process and larger absorption efficiency, which means the light emission yield will be increased even greater compared with the undoped samples. The result of simulation also shows that the optimal molar concentration ratio for co-doped ions and rare earth element is 5.77%, which is close to the experimental result. On conclusion, the co-doping effect of Li, Mg, Al in rare earth oxide produce the deform in the host lattice, the deform will cause the increase of quantum efficiency of the material. This might be one of factors that may cause the increase in light emission yield.关键词：co-doped ions;rare-earth oxide;molecular mechanics;density functional125|58|2更新时间：2020-08-11
- 摘要：For more than one century, the sulfide phosphors have been used as a long-lasting phosphor. However, the sulfide phosphors are not stable and bright enough for many applications. So there has been a great demand for new type host lattices substitutes in recent years. Since scientists firstly reported the green and blue color emitting long-lasting phosphorescence phenomenon from the Eu2+-doped alkaline earth aluminates, the oxide-based long-lasting phosphorescent materials, especially the aluminate-base and the silicate-base luminescent host lattices have attracted more and more attention and have been developed rapidly to replace the conventional long-lasting phosphorescent materials. The compounds with perovskite structure are a kind of important luminescent hosts and were paied attention to by researchers in recent years. For example, CaTiO3:Pr3+ was found that it has a red long-lasting phosphorescence and it shoots a wavelength to locate at 613nm, which belongs to the 1D2→3H4 transition of Pr3+. The red phosphor SrTiO3:Pr3+,Al3+ was synthesized and found that there exists the energy transfer to Pr3+ from co-doped Al. Although stannum is not the same group elements with titanium, its four value states are quite stable and form perovskite structure with alkaline-earth metals oxides. The titanates and stannates of alkaline-earth metals should be one of important materials with afterglow properties as alkali-earth aluminates. The novel phosphors, CaSnO3:Pr3+ are prepared by the conventional high-temperature solid-state method and their luminescent properties are systematically investigated. XRD, photoluminescence, long-lasting phosphorescence and thermoluminescence spectra are used to characterize the synthesized phosphors. After irradiation under 254nm UV light, these phosphors emit near white light and their phosphorescence can be seen with the naked eye in the darkroom clearly. The result of our research reveal that the CaSnO3:Pr3+ phosphor maybe a novel practical long-lasting phosphorescence phosphor. This is the first time observation of long-lasting phosphorescence in alkaline-earth stannates with perov-skite structure and is of value significance in both realizing mechanism of long-lasting phosphorescence and developing new long afterglow materials of practical application.关键词：CaSnO3;praseodymium ion;long-lasting phosphorescence;perovskite107|81|2更新时间：2020-08-11
- 摘要：Due to a lot of advantages, such as energy saving, high efficiency and long lifetime, white light emitting diode (W-LED) has been widely applied in many areas. The common way to fabricate W-LED is by painting a yellow-emitting phosphor on the blue LED chip. Since blue LED emits from 430nm to 480nm, the absorption energy for a better yellow-emitting phosphor should match that spectral region of LED emission. YAG:Ce3+ shows a strong broad band absorption around 465nm and emits at about 540nm; therefore it has been used as the main yellow-emitting phosphor in W-LED. However, the weakness of W-LED composed of blue LED and YAG:Ce3+ is the shortage of its red-emission component. To overcome this weakness, one of the following approaches could be chosen: 1.Adding some red-emitting components into YAG:Ce3+ phosphor; 2.Doping other cations in YAG:Ce3+ lattice. Lanthanide ions are the appropriate ones for this doping YAG:Ce3+ since their ionic radii are very close to that of Y3+ ion. Many papers have reported the study on lanthanide doping. In this paper, the doping effects of Pr3+ and Sm3+ on the luminescence properties and fluorescence lifetime of YAG:Ce were systematically studied in order to understand the rule. Phosphors were synthesized by high-temperature solid-state reaction under reducing atmosphere. The X-ray diffraction patterns presented Pr3+ and Sm3+ can partially replace Y3+ and the lattice phases do not change. The doping effects of Pr3+ and Sm3+ on the luminescence properties and fluorescence lifetimes of (Y0.96-xLnxCe0.04)3Al5O12 (Ln= Pr3+,Sm3+) were studied. The emission and excitation spectra of the samples are recorded. In the (Y0.96-xPrxCe0.04)3Al5O12 system the emission band of Pr3+ was at about 609nm; and in the (Y0.96-xSmxCe0.04)3Al5O12 system the emission band of Sm3+ was at about 616nm. So it can increase the color rendering index (CRI) of YAG:Ce phosphors doped by Pr3+ or Sm3+. Fluorescence lifetimes of the Ce3+ in (Y0.95Pr0.01Ce0.04)3Al5O12, (Y0.95Sm0.01Ce0.04)3Al5O12, (Y0.96Ce0.04)3Al5O12 are measured. The lifetime decreased due to the doping of Pr3+or Sm3+ in YAG:Ce3+.关键词：W-LEDs;YAG：Ce;emission spectra;doping108|114|8更新时间：2020-08-11
- 摘要：Strontium aluminates doped with europium and dysprosium have been attracting people's attention for their great stability, high quantum transformation rate and fine luminescence performance. The preparation and spectra properties of yellow-green phosphor SrAl2O4:Eu2+,Dy3+ and blue-green phosphor Sr4Al14O25 :Eu2+,Dy3+ are commonly researched while those of SrAl12O19:Eu2+,Dy3+ is rarely studied. In this paper, SrAl12O19:Eu2+,Dy3+ violet fluorescent powder was synthesized using SrCO3 and Al2O3 as raw materials employing high temperature solid-state reaction, whose emission spectrum located at 395nm. The crystal structure was analysised by X-ray diffraction(XRD) when nSr:nAl=1:12. The XRD results suggested the characteristic peaks of Sr4Al14O25 gradurally decreased while those of SrAl12O19 increased by degrees when reaction temperature rised from 1150℃ to 1250℃. That's to say, the change of reaction temperature brought about the transformation of crystal structure. The excitation and emission spectra were tested by fluorescence spectrophotometer. When the reaction temperature was 1150,1200,1250℃ respectively, the ratio of Sr and Al differed from 1:6 to 1:18 in order to investigate the corporate effect of matrix composing and reaction temperature on spectra properties. According to the binary phase diagram of SrO and Al2O3, the lower of SrO content and the higher of Al2O3 content, the higher of the reaction temperature of corresponding strontium aluminates. With the content of Al in matrix increasing and reaction temperature rising, the transformation of crystal structure might change the crystal field environment, leading to the variety of emission spectra. The emission spectra shifted from 490nm to 395nm. The luminescence intensity of SrAl12O19:Eu2+,D+ t to be the strongest under the condition that nSr:nAl=1:12 and reaction temperature was 1 250℃. The decay curve investigation was also tested in fluorescence spectrophotometer, which showed SrAl12O19:Eu2+,Dy3+ has no afterglow performance, which may correspond with the spinel structure of SrAl12O19. The preparation and spectra properties of SrAl12O19:Eu2+,Dy3+ violet fluorescent powder were studied. The effect of reaction temperature and the matrix composing on crystal structure and emission spectra was investigated. The research may be helpful for correlative workers.关键词：SrAl12O19;Eu;Dy;solid-state reaction;emission spectra103|62|1更新时间：2020-08-11
- 摘要：The second group metal tungstates have attracted particular attention because they have practical importance as laser host materials in quantum electronics and scintillators in medical applications. The luminescence of SrWO4, which can be excited by short-wavelength ultraviolet radiation, X-rays, cathode rays etc., mainly shows a blue emission spectrum. It is generally agreed that a thin film phosphor has superior resolution compared to powders because of its smaller grain size and less lateral scattering. Less extensive investigation has been made on the preparation of the SrWO4 films. A variety of physical and chemical deposition methods including sputtering deposition, electron beam evaporation and electrochemical method have been reported for the preparation of SrWO4 films. In addition to these techniques, spray pyrolysis method is very interesting because of its advantages of no vacuum, simple instrumentation and low cost. In this paper, SrWO4 films were prepared on glass substrates by spray pyrolysis. The effects of preparation conditions and monovalent, bivalent and trivalent cation doping on cathodoluminescence (CL) properties of the films were studied. Polycrystalline SrWO4 films formed a scheelite structure after being annealed above 300℃. They exhibited cathodoluminescence consisting of a blue emission band at 448nm and a blue-green emission band at 488.6nm. The blue and blue-green emission intensities increased with annealing temperature. Annealing atmosphere and doping with Ag+ and La3+ did not influence the characteristics of the blue and blue-green emissions, whereas Eu3+ did. The results indicated both the blue and blue-green emissions originated from the charge transfer transition of WO42- groups.93|87|0更新时间：2020-08-11
- 摘要：Gallium nitride and its ternary alloys have been attracting much attention because of their unique physical and chemical properties and their great potentialities for semiconductor industrial applications, such as light emitting diodes(LEDs), laser diodes(LDs) operating from green to ultraviolet(UV), UV-detectors and microwave power devices. The primary object of this study is to investigate the influence of different thickness of Fixed-Indium-Content InGaN layer on the shift of the photoluminescence(PL) spectra and optical absorption of the whole system structure. Photoluminescence(PL) and absorption properties of the Fixed-Indium-Content InGaN/GaN heterojunction single quantum well (SQW) structures have been investigated using photoluminescence spectrum and ultraviolet-vi-sible spectrophotometer at room temperature, respectively. The films were grown by metal-organic vapor phase epitaxy (MOVPE), using GaN buffer layer on sapphire substrates. The width of InGaN layer (<3nm) in the SQW was varied while keeping other growth parameters fixed. Sample A has an InGaN active layer of thickness 1.5nm, and Sample B has an InGaN active layer of thickness 2.5nm. Two samples were capped with a 25nm GaN layer. PL measurements show that the PL peak position (432nm in Sample A and 465nm in Sample B) was redshifted by 33nm, the intensity was reduced about 8%, and the full width at half maximum (FWHM) of PL spectrum increases with increasing (1nm) of the potential well layer width. The spectra of transmission and reflection show that transmission T is very high there can be only few reflection R as no absorption R+T exceeds 100% in the near infrared ranges for the sample with InGaN layer of thickness 1.5nm. The reasons of these results are discussed. The significance of these studies is multifold and these results provide further information of importance toward the design optimization of optoelectronic devices employing the Ⅲ-nitrides.关键词：InGaN/GaN;single quantum well;photoluminescence;transmission spectra;reflection spectra109|89|3更新时间：2020-08-11
- 摘要：The fiber-optic weigh technology is the process to estimate the gross weight of the loads, by measu-ring the loads forces acting on the weigh system with fiber-optic sensing technology. Several fiber-optic weigh system have been reported by prior authors, such as the microbending system, the polarimetric system and the interferometric system. Here, we demonstrate a novel weigh system based on fiber Bragg grating(FBG) sen-sing technology. The sensing principle of FBG is that: when the physical quantity, strain or temperature, monitored by FBG sensors changes, it will cause the reflected wavelength shift of the FBG sensors. This wavelength shift is proportional to the variation of strain or temperature. Compared with other fiber-optic systems, the FBG-based weigh system, which is simpler in design and easier to be integrated, can offer higher accuracy, longer lifetime, and lower costs simultaneously. In the weigh system, the load-supporting structure is very important. In this experiment, a metal cantilever beam was chosen as the elastic body of the weigh system to support the loads. With the theory of the strength of materials, we analyzed the cantilever beam structure and deduced that the force on the free end of the cantilever beam was direct proportion to the deflection variation of the beam. We could use a FBG to detect the deflection of the beam to calculate the force on the free end of the beam. Based on this conclusion, we designed the cantilever beam with special parameters to meet this weigh system. We also used the ANSYS software to calculate the deflection of the designed cantilever beam, and the result showed that this metal cantilever beam was suitable for this weigh system. In this experiment, in order to use the FBG detect the deflection variation of the cantilever beam, one end of the FBG was adhered on the free end of the standard cantilever beam with special gelatin, then the FBG was dragged to make the FBG reflected wavelength shift about 1nm. Finally, the other end of the FBG was adhered on the motherboard of the weigh system. The bonding coefficient of the gelatin is about 0.93. When the loads were applied to the end of the cantilever beam, it caused the deflection of the beam, and this caused the FBG deformation along the fiber longitudinal direction. A fiber grating interrogator was applied to detect the wavelength shift of FBG. The best resolution of the interrogator is 1 pm, and the scan rate of the interrogator can reach 5 000 Hz. According to monitoring the wavelength shift of the FBG, the deflection variation of the cantilever beam could be obtained. After analyzing the cantilever beam structure, we could derive the mathematic relationship between the loads applied to the end of the beam and the flexivity of the beam, and the weight of the applied loads could be made out by the value of the flexivity. The experiment results demonstrated that the weight range of this system could reached about 50 kg, the sensitivity of this system was about 0.05 kg, and the related linear regression coefficient is 0.9997.关键词：fiber Bragg grating;micro-flexivity;cantilever beam;ANSYS119|126|3更新时间：2020-08-11
- 摘要：CdSe semiconductor QDs with diameters ranging between 1.5 and 8nm exhibit strong and tunable luminescence. They have been widely investigated because of their potential use in sensors, laser materials, thin film light-emitting devices (LEDs), and biological labels. Among numerous possible applications of CdSe nanoparticles, biological labeling will be pointed out. However,highly luminescent CdSe nanocrystals were usually synthesized with hydrophobic organic capping agents, such as trioctylphosphine/trioctylphiosphine oxide (TOP/TOPO), which limits their applications in biology. To overcome this limitation, several synthesis strategies have been used. This work presents that hydrophobic CdSe quantum dots (QDs) were successfully transferred from nonpolar organic solvent to biocompatible water buffer by liposome encapsulating technology. And this result has been confirmed via transmission electron microscopy (TEM), fluorescence mapping, and photoluminescence (PL), respectively. TEM image showed free CdSe QDs are spherical and nearly monodispersed, having an average diameter of 3nm. Average size of QD-liposome is approximately 20nm. TEM images showed that QDs have been encapsulated in the liposome. Fluorescence mapping successfully showed the luminescence intensity distribution of liposome-entrapped QDs (QD-liposome). Photoluminescence indicated that QDs-Lip basically retain optics quality of free quantum. This phenomenon can be attributed to liposome transfer with TOPO molecules that stabilize the surface of QDs, via hydrophobic interaction between double molecule chain of lipid with CdSe surface on the TOPO ligand, form a bilayer structure with TOPO molecules that stabilize the surface of QDs, keep CdSe exist environment. As a result, QDs-Lip possesses high emission efficiency.关键词：liposome;CdSe;quantum dots;biocompatible128|155|5更新时间：2020-08-11
- 摘要：Water-soluble CdSe nanocrystals were synthesized in the system of Na2SeSO3 and Cd(CH2COO)2 by using L-cysteine hydrochloride (L-Cys) as a stabilizer. Lysozyme (Lys) was labelled by the CdSe nanocrystals to investigate the application of CdSe nanocrystals as a fluorescent label which can be connected to the biologic molecule easily by the L-Cys over around the nanocrystals. There are more choice to label the biologic reagents because of the-NH2 and-COOH of Lys. The powder of CdSe nanocrystals was characterized by transmission electron microscopy (TEM) and the optical properties was investigated by fluorescent spectral analysis and fluorescent microscope. It was proved that different CdSe nanocrystals with different sizes and optical pro-perties can be synthesized in different reaction condition. The peak wavelengthes of emission and absorption spectra of the CdSe nanocrystals are at about 530 and 410nm, respectively. After labeling, the full width at half maximum (FWHM) of CdSe nanocrystals can be kept well which was about 40nm and easy to distinguish during labeling the biologic reagents. Comparing with the optical properties before labelling, the emission maxima of the obtained CdSe nanocrystals have a little shift, just about 2nm, but the emission intensity of CdSe nanocrystals-labelled lysozyme can took a great enhancement about 100% with the change of the consistence of Lys. In sum, the L-cys-stabilized CdSe has an important value as a fluorescent label.关键词：L-cysteine hydrochloride;CdSe nanocrystals;luminescent material;fluorescent label;lysozyme116|82|0更新时间：2020-08-11
- 摘要：We reported the preparation of polycrystalline sub-micro ZnO powder using a two-step microwave-assisted synthesis method in which urea and zinc nitrate was used as precipitate to form a uniformity deposition and microwave radiation was employed to form spherical for polycrystalline ZnO particle. The as-prepared ZnO powder was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectra (PL). The results showed that zinc nitrate was in decomposing urea solution at 90℃ accompany by methyl methacrylate for 2 h. After microwave-assisted radiation, the uniform ZnO spheres were obtained and the par-ticle size was about 50~100nm. For comparing, the non-microwave-assisted sample was also characterized which were c-axis oriented and in rod-like shape. The mechanism on preparation of spherical ZnO powder was discussed in this work. By treatment of microwave radiation, the precursor could be heated in uniform so that Zn2+ and O2-on the surface resolved homogeneously and to promoting spherical ZnO particles easily. X-ray powder diffraction patterns of ZnO sub-micro particles are illustrated. All peaks can be well indexed to the zincite phase of ZnO. No peaks from any other phase of ZnO and impurities were observed, it indicated the high purity of the obtained ZnO sub-micro particles. The PL spectrum showed that there were two main emission peaks in near ultraviolet and visible region respectively. The violet emission located at 420nm with a FWHM of 60nm was assigned to a donor-acceptor-type transition or radiative recombination of electrons in conductive band and holes from the valence band. The blue one at 470nm with 30nm FWHM was at-tributed to recombination of trapped electrons and holes from the valence band. ZnO particle morphologies were very complex and diversiform in comparison with that of any other semiconductor. So far, monodispersed ZnO particles with well-defined morphological characteristics, such as, ellip-soidal, needle, prismatic, and rod-like shapes have been obtained, but spherical shape have not been discussed extensively. This paper pointed out a new application of microwave technology in the preparation of spherical ZnO.关键词：uniformity deposition;microwave-assisted;spherical ZnO;PL spectrum93|75|3更新时间：2020-08-11
- 摘要：At present, field emitting cold cathode materials, including molybdenum, silicon, diamond carbon films, diamond-like carbon films and carbon nanotubes, are being developed. With each of these materials having their own shortages, it is important to seek some new field emitting cold cathode materials. Lanthanum hexaboride (LaB6) is a material with low work function, low resistivity, low sputtering yield, high melting point and high chemical stability. It has been widely used as thermionic emitters. On the other hand, LaB6 is also an excellent material for use as field emission cathodes. Some field emitting cold cathode single tips in-cluding LaB6, molybdenum, tungsten and tungsten rhenium were fabricated by using electro-chemical etching method. The electron emission characteristics of these cold cathodes were studied in a diode test cell in vacuum system. Changing the anode voltage at a pressure of 1×10-3 Pa, the current density of single crystal LaB6 was compared with other material cathodes. It showed that LaB6 was one kind of excellent materials to act as field emitting cold cathode, whose current density was much higher than any other materials. In addition, LaB6 field emission arrays were attempted to be fabricated by using electro-chemical etching method. The a-type si-licon layer was depositing by PECVD as mask. Electrolytes in this process were ethanol (CH3CH2OH) containing 2% hydrochloric acid (HCl) and the electrolytic current was 0.6 mA. The SEM showed that the substrate and surface of single crystal LaB6 tips were both smooth. The height of LaB6 tips was about 1.7μm. The uniformity of the tips was fine, while due to the erosion selectivity for different crystalloid surface in electro-chemical etching method, serious anisotropic phenomenon was observed for LaB6 tips. It demonstrated that, seeking some new electrolytes or using other special dry etching methods instead of wet etching methods, maybe effective to fabricate excellent LaB6 field emitting cold cathode tips. These experimental conclusions were constructive to direct the application of LaB6 to field emission cathodes further.关键词：single crystal lanthanum hexaboride;field emission arrays;electro-chemical etching method;anisotropic phenomenon104|118|3更新时间：2020-08-11
- 摘要：By introducing a trifluoromethyl group on 5-position of the pyridyl ring of 2-benzo[b]thiophen-2-yl-pyridine, a new red emission iridium complex [(btfmp)2Ir(pic)] using pyridyl-2-carboxylic acid as ancilary ligand was synthesized and characterized. We observed that a CF3 substituent on the 5-position of the ligand can decrease in the bandgap between the HOMO and LUMO levels, so as to result in large red shift of the emission band, but pyridyl-2-carboxylic acid acted as the ancilary ligand lead to emission shifting to blue. As a result saturated red light emitting EL based on red emission at 637nm from the iridium complex was observed, a peak luminance efficiency of 3.0cd/A, and the CIE color coordinates of (x=0.65, y=0.29) which are almost not changed under the varied driving current were obtained.关键词：iridium(Ⅲ) complex;red electrophosphorescence;OLEDs104|18|3更新时间：2020-08-11
- 摘要：With N,N-dimethyl-quinacridone (DMQA) heavily doped into tris-(8-hydroxyquinoline) aluminum (Alq3) as emission layer, a super-linear luminance enhancement with the increase of current density in organic light-emitting devices was observed. When the concentration of DMQA was 1.6%~5.6%(in mass fraction) and the current density excess 300mA/cm2, contrary to the roll-off in electroluminescence (EL) efficiency, the EL efficiency ascends with current density. About~0.22 cd/A enhanced EL efficiency is observed from 300mA/cm2 to 700 mA/cm2, which is believed to be contributed to the extra regenerated singlet excitons resulted from T-T annihilation.关键词：T-T annihilation;DMQA;OLEDs112|48|1更新时间：2020-08-11
- Address：No.3888 Dong Nanhu Road, Changchun, Jilin, China Postal code：130033
- Tel：0431-86176862 Email：fgxbt@126.com
- Technical support is provided by Beijing Founder electronics co., LTD 吉ICP备11002662号-17
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0