最新刊期
卷 21 ， 期 2 ， 2000
- 摘要：The transmission intensity of ZnCdSe quantum well/CdSe quantum dot combination structure vs delay time is investigated using femto-second pump-probe measurement.Femto-second pulse with pulse width 130fs and wavelength 537um utilized as pump and probe pulse in the pump-probe measurement is yielded using locking mode Ti:sappire femto-second laser(Spectra-physics laser Co.)and tuned by OPA-800.The transmission intensity of probe pulse vs the delay time between pump pulse and probe pulse is detected using multiplier phototube.The structure of experimental sample is ZnSe buffer/7um ZnCdSe(QW)/15um ZnSe barrier/10um CdSe(QD)/ZnSe.ZnSe,ZnCdSe and CdSe were grown on GaAs substrate by molecular beam epitaxy,and then the GaAs substrate is eroded by corrosive.The absorption peak of exciton in ZnCdSe quantum well of experimental sample is located at 528um.The transmission intensity characteristic with the delay time of probe pulse is shown in Fig.4.On the basis of the condition of experiment,we consider the rise-time of turn-on side is primarily determined by pump pulse lineshape and the down time of turn-off side is donated from exciton decay in ZnCdSe quantum well.Fitting the data of pump-probe experiment,the rising time of 367±60fs and the down-time of 1.3±0.2ps are obtained.Extracting the donation of pulse lineshape in down-time,the exciton decay time is 1ps calculated from turn-off side of the pump-probe transmission curve.关键词：ZnCdSe QW;CdSeQD;exciton;pump-probe measurement134|81|0更新时间：2020-08-11
- 摘要：With the development of magneto-optical technology,the properties of the Polaron in magnetic field have been of considerable interest.Larsen proposed a novel operator method to investigate the properties of 2D Polarons.Peeters et al discussed the properties of the magnetopolaron using the Feynmann path-integral approach.Wei and co-workers studied the induced potential and the self-energy of an interface magnet-opolaron using the Green-function method.The properties of the surface magnetopolaron have been discussed by the method of a linear-combination operator and a perturbation by the present authors and co-workers.In fact,so far research on the polaron has been restricted to approximation and calculation where the electron spin and the interaction between phonons of different wave vectors in the recoil process are neglected.There is weak bulk but strong surface coupling between the electrons and phonons for semi-infinite TIBr crystal in a magnetic field.So far,research into this has been very scarce.The purpose of this present paper is to explore the effects of the electron spin and the interaction between phonons of different wave vectors in the recoil process on the properties of the surface polaron in magnetic field.With both the weak coupling between the electron and bulk LO phonon and the strong coupling between the electron and SO phonon included,an expression for the effective Hamiltonian of the surface magetopolaron is obtained.With considering the electron spin and the corresponding interaction,the influence on the effective Hamiltonian,vibration frequency,induced potential and effective interaction potential of the surface magnetopolaron in semi-infinite TIBr crystal are investigated by a linear combination operator and perturbation method.Numerical calculations for a TIBr crystal,as an example,are performed,and some properties of the vibration frequency and the induced potential of the surface magnetopolaron are discussed.关键词：surface magnetopolaron;spin;interaction between phonons;vibration frequency;induced potential89|127|2更新时间：2020-08-11
- 摘要：In our earlier papers on theoretical analysis of fluorescent cooling,it is pointed out that there are two kinds of basic physical mechanism-anti-Stokes fluorescent cooling in single center(ASFCSC)and anti-Stokes fluorescent cooling by energy transfer(ASFCET).Doubtless,ASFCSC is an important process and dominants in fluorescent cooling of solid,but ASFCET can exist at the same time.Actually,the excitation transfers of rare-earth ions have been studied a lot even for ytterbium ions in fluoride glasses.Many experiment Phenomena show it is possible for ASFCET to realize.In this paper,we discussed the most cooling efficiency in ASFCET,which is a fluorescent cooling mechanism based on energy transfer among the centers within the inhomogeneously broadened spectral profile.A model was developed to evaluate the fluorescent cooling under the mechanism.We discussed it in two situations: two-phonon-assisted energy transfer process with small energy mismatch and one-phonon-assisted energy transfer process with large energy mismatch.The dependence of the most cooling efficiency on excitation photon energy and temperature was given.When the inhomogeneous line width is narrow,the best pump light frequency does not change with temperature and the most cooling efficiency is proportional to the cube of temperature.When the inhomogeneous line width is wide,the difference between the best pump light frequency and the center frequency of the inhomogeneous line gets wider as the temperature goes lower.The difference changes rapidly at low temperature.The most fluorescent cooling efficiency produced by energy transfer tends to lower with temperature decreasing,and trends to zero finally.The regularities by which fluorescent cooling efficiency lower with temperature are correspond to the results obtained in experiments.关键词：laser cooling;Anti-Stokes fluorescent cooling;pump frequency;cooling efficiency;energy transfer101|133|0更新时间：2020-08-11
- 摘要：The main problem in laser cooling investigation is to choose materials.One of the keys is the energy width split out between ground state and excited state of luminescence center.Choosing the energy space reasonably will help us to determine laser-cooling media correctly.The energy gap of two states determines two important elements in laser cooling,quantum efficiency and multiphonon relaxation rate.Only as for cooling power in laser cooling,the more the energy gap splits,the higher quantum efficiency is and the more powerful is to fluorescent cooling.When the energy gap reaches a certain width or more,the cooling power will almost keep unchanging.If heat-light converting efficiency is considered in laser cooling,the energy gap in reason should be much narrower.If we confirm that it is the most important to keep cooling power at the highest level,then,it is more appropriate to choose the energy gap at 5000cm-1than 10000cm-1of Yb3+,because,the choosing can not only confirm higher heat-light converting efficiency,but also ensure in substance a high cooling power.关键词：laser cooling;Anti-Stokes fluorescent cooling;energy gap;heat-light converting efficiency90|104|2更新时间：2020-08-11
- 摘要：By using n-butylamine as carbon resource,a layer of carbon film is covered on the porous silicon(PS)surface by means of radio frequency glow discharge.Raman spectra and IR spectra of the carbon film indicate that there are amino-groups and hydrogen atoms in the carbon film.IR spectra exhibit that the surface of the treated sample is mainly covered with Si-C Si-N and Si-O.Compared with the sample without the treatment,the photoluminescence(PL)intensity of the treated sampie is 4~4.5 times stronger,and the 30um blueshift of the PL peak was observed experimentally; furthermore,the intensity decay and the blueshift of the PL peak has not been observed after storing for 60 days in the atmosphere.It is presented that the enhancement of the PL intensity and stability of the treated sample is due to the existence of Si-C,Si-N and Si-O on the PS surface simultaneously,and blueshift of the PL peak is attributed to aminogroups and hydrogen atmos in the carbon film.The results show that carbon films can be an excellent passivation films on porous silicon and may be good to the practical application.关键词：porous silicon;carbon film;surface passivation;fluorescence spectra101|114|0更新时间：2020-08-11
- 摘要：The structure of unintentionally doped GaN grown by organometallic vapor phase epitaxy on Al2O3substrates was investigated using Rutherford Backscattering and Ion Channeling measurements.The growth of unintentionally doped GaN films was performed by MOCVD method using a home-made vertical reactor operating at atmospheric pressure.The grwoth was carried out on(0001)oriented sapphire substrates using Trimethylgallium(TMGa)and blue-ammonia(NH3)as Ga and N sources,respectively.The mixed gases of hydrogen and nitropen were used as the damer gases.A thin buffer layer with thickness of about 15um was grown at 520t and recrystallized at 1060℃ for 6 minutes.The GaN films were grown at 1060℃.Rutherfold Backscattering and Channeling spectra were measured with 2.0meV He+ions at a scattering angle of 165°.The ion channeling minimum yields in the near-surface region(the ratio of the backscattered yield along the random direction to that of the aligned,Xmin)for four samples were 1.43%,2.13%,2.22% and 29.8%,respectively.The electrical properties of those films were measured by Van der Pauw Hall method,and their compensation ratio were 0.45,0.6,0.83 and 0.9,respectively.The results indicats that there existed some relationship between Xminand the compensation ratio,and the relation was unambiguous for thin films.The value of Xminwas small in GaN with light compensation ratio,while it was large in GaN with heavy compensation ratio,but the growth in value Of Xminwith increasing of compensation ratios was seen to be nonlinear.The experimental results were analyzed as following: high compensation suggested that there were many acceptor impurities or defects in epitaxial films of GaN.When those acceptor impurities or defects were interstitial,the incident He+ions would endure great scattering so that the channeled yields would increase remarkably.But as for thick epitaxial film,most part of defects were located near the interface between film and substrate,so it was possible that the crystalline quality near the film surface would be improved.In this case,the growth of compensation didn’tresult in alarge increment of Xmin.However,in the thin films with heavy compensation,some cases were different.The acceptor impurities or defects were to be distributed over the whole epitaxial film,and near surface there still existed many impurites or defects,therefore,the value of Xminwould increase greatly.关键词：GaN;ion channeling;compensatio87|111|0更新时间：2020-08-11
- 摘要：The GaP surfaces were passivated withCH3CSNH2solution of certain concentration at 90℃ temperature.The effect of passivation for different treatment time on the surface structure,morphology and electronic features was investigated using scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS).First,the treatment time of about 20min.was determined to obtain a uniform passivation film on the GaP surface.This means that the wet chemical reactions were completed in a certain interval of time when the GaP wafer was dipped in the CH3CSNH2solution.It is found that the oxide overlayer on the GaP surface has been removed basically.The chemical reaction between the Ga atoms and the S2-ions dissociated from theCH3CSNH2solution has taken place under the condition of certain temperature.The XPS measuremnet results indicate that the gallium sulfide and phosphor us sulfide have been formed on the surface during the passivation.After passivation the XPS peaks of Ga 3d and P2p are shifted to higher binding energy by about 0.1-0.5eV.0.2~0.4eV from those of the bulk GaP and their full widths at half maximum(FWHMs)are increased,respectively.The P 2p band has been resolved into two component bands by a curve fitting technique.The fitted band peaked at 129.2eV corresponds to free atom state of P,whereas the other fitted band peaked at 128.5eV corresponds to compound state of P.These chemical shift are consistent with electronegativity and binding energy of sulfur.The passivated surfaces were further sputtered by Ar+ ion for 2min under the condition of voltage SKV,current density 100uA/cm2.It shows that the Ga 3d,P2p,S2p peaks are located at the binding energies of 18.5eV,129.0eV,158.1eV,respectively.Hence it reveals that a thin Soverlayer film has been formed on the GaP surface,which can prevent the oxidation from environment.It possesses a good chemical stability.The XPS measurements identify the presence of both Ga-S and P-S bonding.关键词：CH3CSNH2 solution;chemical passivation;GaP;surface properties82|112|0更新时间：2020-08-11
- 摘要：Si-doped GaN was grown by MOCVD method using a home-made vertical reactor operating at atmospheric pressure.To prevent parasitic reactions in the gas phase,reagents were mixed at 20mm before reaching the substrate.The growth was carried out on(0001)oriented sapphire substrates using Trimethylgallium(TMGa)and blue-ammonia(NH3)as Ga and N sources,respectively.The doping reagents was the diluted silane(SiH4).The mixed gases of hydrogen and nitrogen were used as the carrier gases.A thin buffer layer with thickness of about 15um was grown at 520℃ and recrystallized at 1060℃ for 6 minutes.The Sidoped GaN films were grown at 1060℃with the [V]/[Ⅲ] ratio of 1000: 1 The growth time was an hour with the growth rate in the rage of 1.8-4.0um/h.The photoluminescence(PL),the Van der Pauw Hall method,and the double-crystal X-ray diffraction(DXRD)were used to measure the optical,electrical,and structural data of these films at room temperature.Table 1 is the characterization data of the Si-doped GaN films.Fig.1 shows the electron carrier concentration and mobility of Si-doped GaN as a function of SiH4/TMGa ratio.The carrier concentration varies between 1×1017 and 4×1019cm-3.The relationship between the carrier concentration and the flow rate ratio of SiH4/TMGa is approximately linear.Fig.2 shows the photoluminescence(PL)spectra of Si-doped GaN as a function of the SiH4/TMGa ratio at 300K.The excitation-source was a 15mW He-Cd laser.The band-edge emission and deep-level emission were observed around 370um and 550um,respectively.Very strong band-edge emission without yellow band(limited by the apparatus)was observed in Fig.2-D.Fig.3 shows the intensity of band-edge emission,the intensity ratio between band-edge emission and deep-level emission as a function of the carrier concentration of Si-doped GaN films.The intensity of bandedge emission was highly enhanced and the intensity of yellow emission was restrained with the increasing ofcarrier concentration.As shown in Fig.3,Si-doped GaN films,with carrier concentration of 2×1019cm-3 were obtained.For this kind of film,the intensity of band edge emission is as high as one hundred times of that of unintentional doped GaN and no yellow luminescence can be found.Fig.4 shows the relationships between the SiH4/TMGa ratio and the FWHM of double-crystal x-ray diffraction(DXRD)and the growth rate of Si-doped GaN films.The FWHM of DXRD of GaN films became wider when SiH4/TMGa ratio increased.However,the growth rate decreased from 4um/h to 1.7um/h with increasing SiH4/TMGa ratio.This phenomenon has not been reported to our knowledge.In this paper,Si-doped GaN films with carrier concentration of 2×1019 cm-3,electron mobility of 120.m2/V.s can be obtained.FOr this kind of film,FWHM of the band edge emission at room temperature is only 60meV,and no yellow emission can be observed.In this work,the optimum flow ratio of SiH4/TMGa was 2×10-4.关键词：MOCVD;GaN;photoluminescence;the double-crystal X-ray diffraction(DXRD);the Van der Pauw Hall method81|99|2更新时间：2020-08-11
- 摘要：More and more attention has been paid to the quaternary AlGaInP alloy,which is the novel candidate materials for visible light and short-wave-length optoelectronic devices and solar cells and which has largest direct band-gap among semiconductors matched to GaAs. In this article, the temperature-dependent and excitation-intensity-dependent photoluminescence(PL) spectra are applied to investigate the (AlxGa1-x)0.51In0.49P(x=0.29) alloys lattice-matched to GaAs, grown by metalorganic vapor phase epitaxy(MOVPE). The temperature of samples were kept at 19K during the measuring of excitation-dependent PL spectra with the laser intensity varied within 3 orders of magnitude.For the temperature-dependent spectra,the temperature was changed from 19K to 250K. According to D.J.Mowbray et al.'s results, the turning-point from direct-band to indirect-band of (AlxGa1-x)0.51In0.49P lies in x=0.50, the (AlxGa1-x)0.51In0.49P(x=0.29) alloys show direct-band gap character and a certain ordering structure for the large separation of PL peak energy and the band-gap derived from the empirical equation of Mowbray and for the relatively wider linewidths than the disordered alloys. The PL peak is excitation independent, which might imply there exists no spatially separated centers in direct band-gap quaternary (AlxGa1-x)0.51In0.49P alloys,but shows anomalous temperature behavior,where the PL peak energy changes with temperature and exhibits Z-shape dependence. The PL peak energy decreases with increasing temperature from 19K,a blue-shift of PL peak energy occurs between 55K and 84K,afterwards,the PL peak energy decreases monotonously again. To the best of our knowledge, this is the first time the temperature anomaly is reported for (AlxGa1-x)0.51In0.49P(x=0.29) alloys,which confirms the existence of ordering structure in (AlxGa1-x)0.51In0.49P(x=0.29) alloys in another way.Because the superlattice effect resulted from the ordering structure can lead to both the band-folding effect of conduction band from the L-point to the Γ-point in the Brillouin zone and the splitting of crystal valence-band so as to lead to the separation of light-and heavy-hole band in valence band,our further study shows,however,no valence-band splitting in (AlxGa1-x)0.51In0.49P(x=0.29) alloys,so we speculate,due to the influence of the ordering structure which results in the band-folding effect in the Brillouin zone,the carriers in conduction band get enough energy to transfer from the Γ-band to the L-band when the temperature is above 55K,thus,the temperature anomaly occurs.Above 84K,the carriers from the L-band dominate the luminescence and abide by the general thermal decay principle.关键词：Ⅲ-Ⅴ semiconductor;ordering structure;photoluminescence91|67|1更新时间：2020-08-11
- 摘要：The infrared transmission spectrum of potassium lithium niobate crystal was studied.The result showed that the spectrum properties of the crystal grown from the melt with higher Li2O contents is better than those of the crystal grown from the melt with lower Li2O contents,the latter has an absorption peak at the wavelength of 480urn while the former has not,so when a laser beam pass across the crystal,the optical loss for the former is lower than that for the latter.The reasons for the result are related to the reduction of replace chance of Nb atom at Li atom site in potassium lithium niobate crystal grown from melt with higher Li2O contents.The reduction of optical loss is very beneficial to the increasing of the second harmonic generation efficiency of the crystal.The second harmonic generation properties of potassium lithium niobate crystal were studied.It showed that the potassium lithium niobate crystal has no frequency-doubling performance unless it has necessary Li contents.The second harmonic generation properties will be improved as the Li contents in the crystal increases.The blue-green laser have been obtained by doubling quasi CW-Ti: sapphire near infrared laser in the wavelength range of 890~960um using potassium lithium crystal grown from the melt with Li2O 26mol%,the results showed that the crystal sample has good frequency-doubling efficiency.The means of enhancing the second harmonic generation efficiency of potassium lithium niobate crystal were discussed.It is deduced that the second harmonic generation efficiency will be increased while the light loss of the potassium lithium niobate crystal reduces.关键词：potassium lithium niobate crystal;transmittance spectrum;second harmonic generation102|109|1更新时间：2020-08-11
- 摘要：The luminescence decay curves of Eu3+:Y2O3 nanocrystals with different diameters and same doped concentration were studied.The surface states act as quenching centers in the luminescence,so the measured lifetimes decrease along with the decreases of the particle size.And the luminescence decay curves of nanocrystals with the same diameter and different doped concentrations were also studied.The measured lifetimes decrease with the increasing of the doped concentration.In high dopant concentration,energy transfer between luminescent ions is caused by exchange interaction.The energy transfer between dopant ions accelerates the quenching through the surface states.The surface state and size confinement bring the different influences to energy transfer in nanocrystals with different size nanocrystals.It is obtained that nanocrystals have much higher quenching concentration than that of bulk material and the quenching concentration of 40um nanoparticles is higher than that of 5nm nanopaticles.The reason of the increasing of quenching concentration is analyzed.Impurity and dislocation may act as bulk quenching center.If the same raw materials were used in preparing samples,concentrations of impurity are identical despite the sizes of the nanocrystals.But the configuration of dislocation is influenced by the nanocrystals size.Dislocation in nanocrystals is not stable below a certain critical size.Nanocrystal has hardly any dislocation when its size is smaller than the critical size.Dislocation density of nanocrystals would be much lower than that of bulk material.The number of bulk quenching center is very small.It has been found that nanocrystals have higher quenching concentration than bulk material.However,experimental evidence indicates that the relationship between quenching concentration and the particle size is not a monotonic function.This is because that surface state effect and size confinement effect bring opposite influences to the energy transfers in nanocrystals.So if a appropriate size of nanocrystals is selected and the surface of nanocrystals are decorated,the nanocrystals doped luminescence material,which has high photoluminescence efficiency and high quenching concentration should be produced.关键词：Eu3+：Y2O3;nanocrystals;surface state effect;energy trans106|138|14更新时间：2020-08-11
- 摘要：Green-emitting phosphors of yttrium borophoshate coactivated with Ce3+、Tb3+ and Gd3+ have been prepared for the first time by a single step of firing,using BPO4 and rare earth oxides as reactants.With the aid of emission spectra and excitation spectra,the spectroscopic properties of Ce3+、Tb3+ and Gd3+ and interaction among them in yttrium borophosphate have been studied.In the systems doped with Tb3+,Ce3+ or Gd3+,the energy transfers from Ce3+ to Tb3+,or from Gd3+ to Tb3+ are observed, but in the system activated with Ce3+ and Gd3+,the competitive absorption and individual emission between them are found.After the incorporation of gadolinium into the yttrium borophosphate doped with Ce3+ and Tb3+,the increment of Ce3+ emission intensity is more than that of Tb3+ emission intensity. It is considered that the increment of Ce3+ emission intensity is due to prevention of energy transfer from Ce3+ to Tb3+,and that of Tb3+ emission intensity may attribute to effective energy transfer form Gd3+ to Tb3+.In above system, Gd3+ prevention of energy transfer from Ce3+ to Tb3+ may exists, which makes it impossible that Gd3+ ion absorbs energy from Ce3+ ion and transfer the energy to Tb3+ ion, because 5d energy level of Ce3+ ion is lower than 6I and 6P energy levles of Gd3+ ion. If yttrium is replaced wholly by gadolinium in the matrix,the relative brightness of the prepared phosphor increases,however,x value of chromatic cordinates decreases slightly, so controlling the amount of gadolinium in the matrix will be of advantage to improving the luminescent characteristics of phosphors.98|107|9更新时间：2020-08-11
- 摘要：Color plasma display panel(PDP)is the most promising flat display for the large area display.Phosphors used in PDP are excited with vacuum-ultraviolet radiation.Naturally,the phosphors are required to have a good quantum efficiency in the region below 200um.Some silicates have stronger absorption in the VUV region.Therefore,it is important to investigate silicates.On the other hand,oxyorthosilicates have good thermal stability and chemistry stability,and also are good host for luminescent materials under UV excitation.However,optical properties of Y2-xGdxSiO5: Eu in the VUV range have not been reported up to now.Y1.95-xGdxSiO5:Eu0.05 were prepared at 1200℃ for two hours with NH4F flux by solid-state reaction.Y1.95-xGdxSiO5:Eu0.05 are polymorphic and crytallizable in the monoclinic X2 type with space group B2/b.The excitation spectra of Y1.95-xGdxSiO5:Eu0.05 monitored at 612um consists of a broad band at 220-300um corresponding to the charge transfer band of Eu,and a number of lines which could be assigned to the f-f transition of Eu3+ for 300-540nm,and the strongest excited peak lies at 396nm.The emission spectrum of Y1.95-xGdxSiO5:Eu0.05 phosphors excited under 396mn irradiation consists of four groups of emission lines in the rang of 560-720nm.The maximum emission peak is located at 612urn.One luminescence line at 580nm,three lines at 590-596nm,five lines at 610-630nm and three lines at 685-705nm are assigned to the transitions 5D0→7F0,5DO→7F1,5DO→7F2,5D0→7F4,respectively.When a x(x= 0.2,0.4,0.6)mol faction of gadolinium is incorporated into the host lattice,the location of absorption peaks of Eu3+ shown in VU-vis excitation specturm of Y1.95-xGdxSiO5: Eu0.05 are not changed,but the relative intensities of these peaks decrease with increasing Gd3+ concentration.In the vacuum-ultraviolet region,the new absorption peak near 192nm appears.The intensity of the new peak assigned to the absorption of 6Gj configuration of Gd3+ increases with increasing Gd3+ concentration until 0.4 mol%,and then,the intensity decreases.The intensity of the host absorption band of the phosphors at 150-185nm is enhanced while the intensity of the charge transfer band of Eu decreases with increasing Gd3+ concentration.Generally speaking,when a x mol fraction of gadolinium is incorporated into the host lattice,the luminescent intensity in vacuum-ultraviolet region increases in spite of the decreasing in VU-vis region.That is in favor of enhanching the luminescent intensity of phosphors used in PDP.关键词：Y1.95-xGdxSiO5：Eu0.05;VUV spectra;host absorption band81|99|2更新时间：2020-08-11
- 摘要：Two series of dinuclear complexes of phthalate and 2,2'-dipyridyl with different molar ratio of Eu3+ to Tb3+ and Eu3+ to La3+ have been synthesized,respectively,Their IR absorption spectra,fluorescence spectra and TG-DTA curves have been studied.The synthesis of the complexes(EuxTb1-x)2L3L'(L=phthalate group, L'=2,2’-dipyridyl)was performed through the reaction of the two ligands L' and L with the mixture of EuCl3 and TbCl3 in solution ,and by the reaction of both ligands with EuCl3and LaCl3,the complex of (EuyLa1-y)2L3L' was prepared.The luminescence spectra were taken on a F-3010 fluorescence spectrophotometer at room tempreture.The IR spectra were recorded on a Mattson Alpha Centauri FT-IR spectrophotometer with KBr pellet.The thermal analysis data were recorded on a Shimadau DT-40 thermal analysis instrument.The IR absorption spectra for all the complexes are similar.The spectra are obviously different with those of phthalate(KHL) and 2,2’-dipyridyl. When the complexes were formed,the absorption peaks of νCOOH(1677cm-1)and νC-OH(1287cm-1)disappeared.The anti-symmetric stretching vibrations of carboxylate group(νas) shifted to lower frequencies,whereas the symmetric stretching vibrations(νs)shifted to higher frequencies.These facts showed that phthalate was coordinated to the rare-earth ions.By comparison,there are two strong absorption peaks(1452.3cm-1 and 1578.0cm-1)in 2,2'-dipyridly,whereas they shifted to about 1523cm-1 and 1 616cm-1 in the complexes. It indicates that the chemical bonds have been formed between rare earth ions and nitrogen atoms of 2,2'-dipyridly.111|71|9更新时间：2020-08-11
- 摘要：CaS dopped with rare-earth ions as a kink of powder phosphors has higher luminescent intensity and quantum efficiency.It is also considered CaS phosphors to be direct current electroluminescent material.It is known that in order to be excited by direct current,DCEL phosphor must be covered with surface conducting layer.So the copper-coating process(forming the surface p-type CuxS conducting layer)is important to DCEL.In this paper,a FAAS(Fire atom absorption spectrum)method is used to determine the copper content in the surface of CaS DCEIL powder.The rate of recovery and the relative standard deviation of this method are 99.4%-100.6%,and 0.4%,respectively.The dependence of copper-coating volume on the solution concentration,solution temperature and the processing time was studied experimentally as volume of solution was definite.When temperature of solution and processing time are defined(60),10min),fig.1 shows that the greater part of copper ions are changed into CuxS surface-phase when concentration of copper ions is lower,but when its concentration becomes higher,copper-coating volume is saturated.When processing time and concentration of adding copper ions are selected(10min,10mg’g-1),fig.2 shows that copper-coating volume increases with temperature.As temperature goes on the copper-coating volume is adjacent to the content of adding copper ions.Fig.3 shows that the copper-coating volume increases with the increasing of COPper-coating process time and gradually goes to saturate and that speed of this process is gradually slower down(60℃,1.5ing).By means of this method,the preparation process and electroluminescence(EL)properties of CAS were improved.关键词：FAAS;DCEL;coating-copper;Cas75|98|0更新时间：2020-08-11
- 摘要：In the discussion the deterioration mechanism of difference electroluminescent phosphors was discussed.By using thromoluminescence,it was found that the deterioration velocity of electroluminescent phosphors is determined by distribution of catching level.It was also showed that the deterioration velocity of electroluminescent phosphors is determined by salt halogen ion radius.The electroluminescent phosphors Were made by general way.The raw-min is fired in quartz tubes.which are surrounded by HBr,HCl or S atmosphere during flaring,respectively.We can conclude that the deterioration velocity of electroluminescent phosphors using HBr as atmosphere is slower than that at HCI and S atmosphere.关键词：termoluminescence;ion radius;electroluminescence;deterioration0109|183|3更新时间：2020-08-11
- 摘要：The process of poling decay with time for poled polymer film waveguides was studied,and an integrated optical method to characterize the order parameter and the poled lifetime of the film waveguides was presented in this paper.The side-chain DANS(4-dimethylamino-4’nitro-stlibene)polymer(50% in weight)and the indium tin oxide-(ITO-)coated glass slides were selected as the waveguide material and the substrates,respectively.The cover layer was air.The DANS polymer film waveguides with suitable thick were made by spin coating.Then the films were poled with the corona-poling setup,which had tungsten wire electrode that was parallel to the surface of the waveguide and along the travelling direction of light in the waveguide.The Poling temperature was 130t,the Poling voltage was about 5~7kV,the Poling current was about 2uA,the poling time was 30min and the space between the surface of the waveguide and the electrode was 9mm.Before and after Poling,the anisotropic effective refractive indices were measured using prism coupling technique in the field of integrated optics.The variety of the ordinary and the extraordinary refractive indices before and after poling and their decay with time were derived from the anisotropic mode eigen-equations,and then curves of the ordinary and the extraordinary refractive indices varied with time were obtained.The curve of the order parameter varied with time was presented and fitted with the multiple exponential function using the least square method.It was determined that the poled lifetime is about 1344 days.关键词：poled polymer;order parameter;poled lifetime116|287|1更新时间：2020-08-11
- 摘要：A stable red organic light-emitting device has been realized by doping a red dye tetra-methyljuloidine(DCJT)in electron transporting layer(ETL).The structure of the device was ITO/ CuPc/ NPB/ Alq: DCJT/ MgAg,where copper phthalocyanine(CuPc)was used as a buffer layer,N,N ’-his-(1-napthyl)-N,N’-diphenyl-1,1’-biphenyl-4,4’-diamine(NPB)as the hole transporting layer,tris(8-quinolinolato)aluminum complex(Alq)as ETL,in which DCJT was doped,indium tin oxide(ITO)and MgAg were as the anode and cathode,respectively.The red emission with peak at 620nm and CIE coordinates x=0.63,y=0.37,maximum luminance 4687cd/m2,maximum luminous efficency 0.83lm/W were obtained.The device showed a high stability under 12mA/cm2 current density continuous operation,the half decay time reached 2 500 hours at the initial luminance 150cd/m2 and the change of driving voltage was 0.6mV/hour in the degradation process.If 50cd/m2 is taken as the initial luminance of red device,the half decay time is considered to be 7500 hours.(According to European Broadcasting Union(EBU)standard,for color display the ratios for red,green,blue luminance should be 30%,59% and 11%,respectively,since 100cd/m2 is often used as initial luminance of green emission in degradation test,50cd/m2 should be adapted as the initial luminance for red emission.)关键词：high stability;red light emitting;organic thin film electroluminescence90|108|3更新时间：2020-08-11
- 摘要：Two kinds of trivalent thulium ion complexes used for organic electroluminescent devices have been synthesized.IR emission spectrum from a bilayer structure device utilizing Tin complexes as emitting materials has been observed for the first time.It is clearly to draw the conclusion that the IR emission is ascribed to the electronic transition from 3H4 to 3H6 of Tm3+ ion chelated by ligands which possess higher energy level of lowest excited triplet state than the upper level 3H4.Intramolecular energy transfer should take place from ligands to central ion because of the absence of direct absorption of Tm3+ ion.90|98|1更新时间：2020-08-11
- 摘要：The photoluminescence(PL) properties of poly［(2,5-diphenylene-1,3,4-oxadiazole)-4,4'-vinylene］(O-PPV)are investigated using absorption and excitation measurements for different concentration ratios of solid-state O-PPV/PEO(polyethylene oxide)blends,as well as by comparing PL spectra for dilute solution and soild state pristine O-PPV.The soild film of O-PPV/PEO is prepared to investigate the interaction between polymers.The O-PPV molecules are dispersed into PEO which is used as a inert material in order to change the interaction between O-PPV.In the O-PPV/PEO blends,it is found that the PL spectra excited by 300nm for different concentration ratios are different.There are three peaks in the PL spectra of 1∶100 and 1∶200(O-PPV/PEO)blends,and the relative intensities of peaks at 500nm and 460nm gradually decrease with lowering the concentrations of O-PPV.There leaves one peak at 416nm when the ratio of O-PPV to PEO is below 1∶300, and PL shape does not change any longer.The results show that the solid-state O-PPV emission arises from interchain charge-transfer states due to interchain effects.According to the absorption and photoluminescence spectra of the soild films,it is also believed that there are types of localized and delocalized states in conjugated polymers.The two types of states have different effects on charge-transfer state in different concentrations of solid films.关键词：photoluminescence;charge-transfer states;interchain excited state81|86|0更新时间：2020-08-11
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