最新刊期
卷 27 ， 期 2 ， 2006
- 摘要：High intensity laser beam transmitting in medium can result in amusing phenomena because of the nonlinear interaction between the laser pulse and the medium.Optical soliton is the just due to the balance between the medium responding nonlinearly to the intensity laser and the diffraction of the intensity laser beam,which have been a subject of many studies.The model for discussing optical soliton is nonlinear Schdinger equation(NLS),which is derived from Maxwell’s equations.The optical soliton,according to transverse coordinate and transmitting direction,can be divided into(n+1)D(n=1,2,3) spatial optical soliton that have ndimensions transverse coordinate and one transmitting direction.(2+1)D optical soliton modes are studied in this paper.Starting from nonlinear Schdinger equation(NLS),the condition that the(2+1)D spatial optical soliton in saturable nonlinear medium would be exist or not,and the boundary conditions for numerically calculating the modes were discussed by mathematical analysis method.By numerical analysis,the base-mode and one-order modes were given by pretty figures including slowly varying beam envelope,beam intensity and three-dimension distribution of beam intensity,and the powers of each soliton were given(a.u.).The results indicate that the soliton is not arbitrary but depending on power,for example,if the beam power would not equal to soliton power,the soliton do not exist.This conclusion could be evidenced further in this paper,if setting the fitting starting value(equivalent to power of optical beam),the solution of Schdinger equation are existence,and if starting value is unfitting,then the solution behave surge,none solution.Meanwhile,the influence of the medium saturable nonlinear parameter and wave vector,which is the soliton transmitting in the direction of z,are studied.The results show that if the k,m,n is fixed on,the power is increasing with α becoming bigger.And if the α,m,n is fixed on,the location of biggest power shift to the position with small r value.The conclusions of this paper shows that the soliton has internal structure,and have the instructive action for the soliton researching.关键词：spatial soliton;saturable nonlinear;modes105|147|0更新时间：2020-08-11
- 摘要：With the development of the solid theories and experimental technology,more and more scholars at home and abroad are conducting research on the properties of the magnetopolaron in crystals,there are already many contributions in this field.Peeters et al.studied the properties of the magnetopolaron using Feynman’s path integral method.Wei and her co-workers discussed the properties of an interface magnetopolaron using Green-function method.Zorkani et al.calculated the ground state energy of bound magnetopolaron using the variational method.Larsen studied the properties of the two-dimensional polaron using an original operator method.Xiao et al.discussed the properties of the surface polaron using a linear-combination operator method.Matsura and Lepine studied the problems of polaron which contains many LO phonon branches in polyatomic crystals.Xiao and Hu and other co-workers investgated the many properties of the surface polaron and bulk polaron in polyatomic crystals.Recently Wang and Xiao discussed the excitation state energy of polaron in polyatomic crystals for the first time.The first excitation energy and the mean number of the weak-coupling magnetopolarons in the polyatomic semi-infinite polar crystals were studied by using a linear-combination operator and unitary transformation methods.The results showed that when the electron is approaching infinitely to the surface of crystals,the ground state energy of the magnetopolaron is only the Landau ground state energy,the first excitation energy of the magnetopolaron is twice the Landau ground state energy,and the mean number of phonon is equal to the number of LO phonons and that of SO phonons that each one has coupling with the electron.When the electron is situated in the depth of crystals,the ground state energy of the magnetopolaron is equal to the Landau ground state energy and the energy of LO phonons and SO phonons that each one has coupling with the electron,the first excitation energy of the magnetopolaron is also twice the Landau ground state energy, and the mean number of phonon is equal to the phonon-number of LO phonons concerning depth and that of LO phonons that each one has coupling with the electron,but it is not related to the each branch of SO phonon.关键词：polyatomic semi-infinite crystals;magnetopolaron;weak-coupling;excitation energy;mean number of phonon.99|63|0更新时间：2020-08-11
- 摘要：The UV and VUV spectra of RE ions due to f-d transition have attracted considerable interest recently.Extension of the semi-empirical model for fN configuration to fN-1d configuration has been very successful in simulation of the spectra.However,it generally needs about 30 parameter values and produces many closing-by eigenstates with strong mixing of quantum numbers S,L and J,which makes the results difficult to interpret.On the other hand,as a result of the strong coupling between 5d orbitals and host lattice,the observed spectra contain mainly broad bands,with most fine structures due to 4f crystal-field interaction etc.washed out.Therefore a simplified theoretical description of the spectra is feasible and useful.In 2002~2003,Duan and co-workers proposed a simple model for f-d transition, which was extended to a more applicable form later.In the model,Hso(d) and Hcf(f) are ignored,and HCoul(fd) and Hso(f) are approximated to be Hfdex=-JexSf·Sd and H′so(f)=ληfSfLfSf·Lf,respectively,so that the main energy splitting ΔEi of fN-1d configuration involves only Jex and ληfSfLf,and the relative line strength Ii of f-d transition is expressed with relevant angular momentum quantum numbers.By using both of ΔEi and Ii,the f-d excitation spectra of Sm3+,Eu2+ and the d-f emission spectrum of Nd3+ in solids are interpreted well in Refs.,so are the f-d excitation spectra of Nd3+,Eu3+ and Tb3+ doped in solids elsewhere.For heavy RE ions the effect of Hso(f) is stronger than that of Hex(fd).By interchanging the coupling order of relevant angular momenta and considering the effect of Hso(f) more accurately,the simple model has been extended and reconstructed to suit this case.It has been successfully applied to Er3+ and Ho3+.Application of the simple model and its extension turns out to be less successful for Pr3+ and Tm3+,which is worth further investigating,while the detailed application to Dy3+ containing contributions from non-diagonal elements has been working on.关键词：f-d transitions;rare-earth ions;the simple model;energy levels;intensity135|118|0更新时间：2020-08-11
- 摘要：The afterglow phosphor CaAl2O4:Eu2+,Nd3+ is prepared utilizing the redox reaction of respective metal nitrates and urea by combustion synthesis with ignition temperatures of 600℃.The X-ray diffraction(analysis) showed that it is coincident with the JCPDS Card(No.23-1036) and its crystal structure is CaAl2O4 which belongs to monoclinic phase and the crystal lattice constant is as follows:a=0.8698 nm,b=0.8092 nm,c=1.5208 nm.With the invariable concentration of metallic ions nitrate,a series of phosphor samples were synthesized by altering the ratio of urea and nitrate.The emission spectra and excitation spectra of the phosphor were investigated.The excitation spectra of CaAl2O4:Eu2+,Nd3+ showed a double peak broadband structure.The main peak located at 352 nm and a shoulder peak at 266 nm.The quantity of urea has obvious influence on the emission spectrum of CaAl2O4:Eu2+,Nd3+.When the quantity of urea exceed double of theoretic quantity,adequate reducing gas produced in the process of combustion reaction benefit to the form of Eu2+ luminescent center,so emission spectra of CaAl2O4:Eu2+,Nd3+ consist of characteristic broad band emission of Eu2+.Contrast this,inadequate reducing gas benefit to form of Eu3+ luminescent center,so when the quantity of urea less than double of theoretic quantity,the emission spectra exhibit characteristic narrowband emission of Eu3+.The samples are fired at 1000℃ for 2h in an active carbon atmosphere in order to deoxidize residual Eu3+ to Eu2+ and eliminate impurity brought by combustion synthesis.This is beneficial to promote the performance of luminescence.The decay curves of phosphor with different quantity of urea were measured.The change of urea’s quantity affected on the afterglow character of CaAl2O4:Eu2+,Nd3+ distinctly and the optimal quantity of urea is 5 times of theoretic quantity.When more urea was used in the experiment,the luminescent intensity will decrease and the lasting time will be shorten.关键词：combustion synthesis;long afterglow;urea;crystal structure101|96|3更新时间：2020-08-11
- 摘要：The new Er3+ doped tellurite glass(70TeO2-9B2O3-6Nb2O5-5Na2O-10ZnO) was prepared by the technique of high-temperature melting.The spectral properties,such as absorption spectra and emission spectra of the glass sample have been measured and investigated.The Judd-Ofelt intensity parameters Ωt(t=2,4,6)(Ω2=8.01×10-20 cm2,Ω4=2.09×10-20 cm2,Ω6 =1.15×10-20 cm2),transition probabilities,excited state lifetimes and the branching ratios have been predicted of several Er3+ ions transitions based on the Judd-Ofelt theory.Compared with the other glass hosts,it found that the Ω2 is bigger of Er3+ in this tellurite glass,which shows that the covalency between the Er3+ and O2- is stronger than silicate,germanate,fluorid,bismuthate,and phosphate glass.The transition probability of Er3+ in this tellurite glass is about 492 s-1,indicating that Er3+ ions could have strong transition at 1.5 μm in tellurite glass.The broad 1.5 μm fluorescence was observed under 970 nm excitation,and its full width at half maximum(FWHM) is 73 nm.The emission cross-section was calculated according to the McCumber theory.The cross section was quite large due to a large refractive index of the host.The value of FWHM×σe for Er3+ in tellurite glass is more larger than that of the bismuth,phosphate,germinate and silicate glass.The results showed that the broad and flat 4I13/2→4I15/2 emission of Er3+ ions around 1.5 μm can be uses as an potential optical amplifier for the wavelength-division-multiplexing(WDM) network system.关键词：optical material;tellurite glass;spectroscopic properties;Judd-Ofelt theory97|88|1更新时间：2020-08-11
- 摘要：As the added flux has much more severe effect on the luminescence properties,the influence of Li2CO3/(Li2CO3+K3PO4) flux ratio x(x= Li2CO3/(Li2CO3+K3PO4)) on the luminescence properties of Y2O2S:0.09Ti phosphor has been investigated to obtain the best luminescence and afterglow intensity.The composite flux of Li2CO3 plus K3PO4 was selected because Li2CO3 and K3PO4 flux have been demonstrated in previous study to improve the afterglow intensity in the beginning stage and long time stage,respectively.PL spectra and afterglow measurement were used to analyze the effect of flux ratio on the luminescence and after glow properties of Y2O2S:0.09Ti phosphor.And XRD measurements were carried out to verify the crystal structure.XRD results showed that the single phase Y2O2S:0.09Ti phosphor could be obtained when flux ratio x increases from 0 to 1.0,while the grain growth orientation may change obviously.The fact that excitation spectra are similar in all flux range demonstrates that the flux ratio has little effect on the excitation process.Nevertheless,the emission spectra showed that the intensity of emission peak at 565 nm depended greatly on the flux ratio.Luminescence intensity of Y2O2S:Ti phosphor increased with an increase of Li2CO3 ratio x,then reduced as x over 0.8.On the other hand,afterglow brightness of Y2O2S:Ti was enhanced at appreciate Li2CO3/(Li2CO3+K3PO4) ratio of about 0.4 with an enhanced afterglow brightness(9.1 mcd·m-2) at(decay) time of 30 min.This value is about four times as that of single Li2CO3 doping(2.4 mcd·m-2),and two times as that of single K3PO4 doping(4.3 mcd·m-2).Above results about the effect of flux ratio on luminescence after glow properties could be used to adjust the overall properties of Y2O2S:0.09Ti phosphor.The best afterglow with yellow color is obtained at appreciate Li2CO3/(Li2CO3+K3PO4) ratio of about 0.4,and its afterglow can last over 5 h with recognizable intensity level(0.32 mcd/m2) after the removal of the excitation light.关键词：flux;rare-earth free;Y2O2S：Ti;luminescence;long afterglow89|55|0更新时间：2020-08-11
- 摘要：The phosphor CaSO4:Eu is a interesting material because of its very high sensitivity to ionizing radiations,negligible fading rate and high chemical stability.It has been used in the thermoluminescent(TL) dosimetry of γ-ray,β-ray,X-ray,neutrons and highenergy cosmic rays.In CaSO4:Eu the chemical valence of the incorporated Eu ions can be +3 and/or +2 valence depending on the preparing methods.Most of the published papers about this phosphor were concerned with the thermoluminescent characteristics.Recently its photoluminescent properties attract more and more attentions.In this work the main attention was paid to its near ultra-violet(AUV) emission of the Eu2+ ions in the phosphor CaSO4:Eu.The luminescence spectra of the CaSO4:Eu samples prepared with different methods were measured at room temperature in order to examine the effects of the preparing method on their luminescent properties.Experiments showed that the Ca and Eu sulphate codeposition method is a better one for the AUV emission of the Eu2+ ions in these phosphors.In the concrete,a proportional amount of pure CaCl2 and EuCl3 was solved in deionized water and the co-precipitate was obtained by adding some sulfuric acid to the mixed aqueous solution.After washing by deionized water and drying the co-precipitate was fired at 650750℃ for one hour under a weak reducing atmosphere.In the phosphors CaSO4:Eu prepared with this method the Eu2+ ions are predominant over the Eu3+ ions.In the phosphor the emission comes from the 5d-4f transition of the Eu2+ ions.Its emission peak is at about 386390 nm and its FWHM is about 16 nm.The UV excitation spectrum is composed of two bands peaking at about 274 nm and 323 nm,respectively.They are attributed to the absorption of the 5f-4d transitions of the Eu2+(ions.) When the content x is between 0.003 and 0.024 the phosphor gives a stronger AUV emission,the(strongest) emission occurs when the x is at about 0.02.The increase of the concentration of the incorporated Eu2+ ions makes the emission band shift slightly to the longer wavelength.The results showed that CaSO4:Eu2+ is a good candidate as the phosphors used in the backlight source of PLLCD.关键词：CaSO4：Eu;AUV;luminescence117|55|0更新时间：2020-08-11
- 摘要：The activated Al-Sr alloy powder was put immediately into boiling pure water,with liquid-solid(ratio) of 4:1.The system was kept isothermal and stirred until white hydrolysates appears.The hydrolysates contain the mixture of Sr(OH)2·8H2O and Al(OH)3 in main,included a little Al(OH)3,AlOOH,SrCO3,and 3SrO·Al2O3· 6H2O.After heat treatment at 700℃ for 1 h,the mixture of SrO and α-Al2O3,γ-Al2O3 were formed.As a precursor,the hydrolysates after heat treatment had been used to prepare long after phosphor Eu,Dy co-doped SrAl2O4 at 1300℃ for 1 h.The crystal structure of hydrolysates and Eu,Dy co-doped SrAl2O4 were analyzed by XRD.The luminescent properties of long afterglow material were studied.The(results) showed that the crystal structure of phosphor is β phase SrAl2O4,the emission spectra of Eu and Dy co-doped SrAl2O4 lied near 520 nm,resulted from the character transition of 4f5d-4f of Eu2+ ion.The method can improve afterglow properties dramatically.The initial luminescent intensity of long afterglow material reached 18 cd/m2,and the duration time lasted 46 h.The improved properties are related to precipitation mechanism of AlSr alloy hydrolysates.With this procedure,SrO and Al2O3 will disperse evenly to effectively enlarge the contact area of the components,shorten the diffusive distance.As a result the sintering temperature could be decreased,while the reaction speed and the long afterglow fluorescent properties of the materials could be improved.关键词：long afterglow phosphor;Al-Sr alloy;hydrolyze;strontium aluminate100|53|1更新时间：2020-08-11
- 摘要：For many years,the borate luminescence materials have been paid much attention owing to their properties of low preparation temperature and high luminescent efficiency.In order to search for the new green-photoluminescence material,Ca3La(BO3)3:Tb3+was synthesized by high temperature solid state reaction at a weak reductive atmosphere which was made by the active carbon powder.The samples had been characterized by scanning electron microscopy(SEM),laser-diffraction size analyzer and fluorospectrophotometer.The results showed that most of the crystals were cylindric and the(average) size of the crystals was about 41 μm.Excitation and emission spectrum of the Ca3La(BO3)3:Tb3+and Ca3La(BO3)3:Tb3+,Ce3+ phosphors were measured by the fluorospectrophotometer at room temperature.In analysis of the emission spectrum for Ca3La(BO3)3:Tb3+under 254 nm excitation at room temperature,there are four main emission peaks at 496,549,594,628 nm,among which the intensity of the 549 nm line is the highest.They belonged to the characteristic emission of Tb3+ ions.Besides,the luminescent intensity of the Ca3La(BO3)3:Tb3+powder changed along with different concentrations of Tb3+ ions,and the optimum concentration of Tb3+ in Ca3La(BO3)3 is x(Tb)=0.25.According to the dependence of the concentration of Tb3+ in Ca3La(BO3)3 under the excitation of 251 nm,it was confirmed that the mechanism of concentration selfquenching of Tb3+ 5D4→ 7F5 transition is electric dipole-dipole interaction.The influence of Ce3+ on the emission intensity of Tb3+ was also investigated,after adding low concentration of Ce3+ to the system of Ca3La-(BO3)3:Tb3+,the luminescence intensity increased only slightly,so Ce3+ may not be a good sensitizer to Tb3+ in Ca3La(BO3)3.In addition,it has been confirmed that when a flux,Li2CO3,was added,the 549nm emission corresponding to 5D4→7F5 transition was intensified greatly.Ca3La(BO3)3:Tb3+ phosphor could absorb ultraviolet radiation and emit green light.Compared with the former results of other borate luminescent materials,when Ca3La(BO3)3:Tb3+ phosphor was excited by 254 nm UV light,stable and much stronger green light could be emitted,so it is promising to apply in the production of green fluorescent lamp.关键词：Ca3La(BO3)3：Tb3+;luminescence;concentration quenching;rare earths94|58|3更新时间：2020-08-11
- 摘要：A red Y2O2S:Eu3+,Mg2+,Ti4+ phosphor is synthesized by co-precipitation method using the metal oxide,nitric acid and oxalic acid.Nitric acid is used as a solvent to dissolve the raw materials and then form the nitrate solution,while the oxalic acid is used to form precipitation.Since all of the raw materials are mixed at the molecular level in solution,a highly uniform product is achieved.The morphology and crystal structure of synthesized phosphors is investigated by the SEM patterns and the XRD patterns.The SEM patterns analysis showed that the phosphors prepared by co-precipitation method have very relaxing structure with the particle size of about 5.0 μm.This is due to the realization of the material mixture in molecule scales during the doping process of co-precipitation method.The X-ray diffraction analysis showed that XRD pattern of the sample is coincident with the JCPDS Card(No.24-1424) and the sample has crystal structure of Y2O2S,which belongs to hexagonal and the crystal lattice constant is as follows: a0=0.3784 nm,c0=0.6589 nm.It indicated that the crystal structure hasn’t change with the doping of Eu3+,Mg2+ and Ti4+.The emission intensity of the samples with various concentration of Eu3+,prepared by the co-precipitation and solid-state method,are compared with each other.When concentration quenching of Eu3+ appears,the peak of radioactive spectrum rooting in high excited state of Eu3+ vanishes.So we can analyze qualitatively about the amount of Eu3+ admitted to enter the crystal lattice through comparing the change of I587.6/I627.0 when Iλ is defined as the intensity of emission peak located at wavelength λ.The result shows that I587.6/I627.0 of the phosphor prepared by solid-state method obviously decreases with the increasing of concentration of Eu3+,while it is steady with co-precipitation method.So the co-precipitation synthesis method can make the Eu3+ enter into Y2O2S host more easily and form more effective luminescent centers than that synthesed by solid-state method.关键词：co-precipitation;emission spectra;Y2O2S：Eu3+;Mg2+;Ti4+94|55|2更新时间：2020-08-11
- 摘要：The sample of YLiF4:Er3+,Tm3+,Yb3+ is synthesized by hydrothermal method.The mol fraction of Er3+,Yb3+ and Tm3+ is 1%,1.5% and 2%,respectively.The emission of YLiF4:Er3+,Tm3+,Yb3+ excited by 355 nm is blue light with the peak in 450 nm which comes from the transition of 1D2→3F4 of Tm3+.After excited by 378 nm,YLiF4:Er3+,Tm3+,Yb3+ emits green light with the main peak in 552 nm.The color of upconversion luminescence of YLiF4:Er3+,Tm3+,Yb3+ excited by 980 nm is white color.The upconversion spectrum exhibits distinct emission peaks at 665(651),552(543),484 and 450 nm.There is another peak around in 648 nm.The strongest is the light with the wavelength of 665 nm(651 nm).The blue light comes from the transition of 1G4→3H6 and 1D2→3F4 of Tm3+.The green light results from the transition of 4S3/2(2H11/2)→4I15/2 of Er3+.It is proved that the red light originates from the transition 1G4→3F4 of Tm3+ and the transition of 4F9/2→4I15/2 of Er3+.The excitation spectrum monitored by 665 nm is different to that monitored by 552 nm.There is an excitation peak corresponding to the energy level 1G4 of Tm3+ in the excitation spectrum of 665 nm.But there is no corresponding peak in the excitation spectrum of 552 nm.It is concluded that there is energy transfer processes between Er3+ and Tm3+ ions.In the double-log coordinate system,the slope of the emission of 484,552 and 665 nm is 2.25,2.28 and 2.21,respectively.The slope of the emission of 359 nm is 2.85.According to this power law,The emission of 484,552 and 665 nm are all due to two photon process,while the emission of 359 nm is due to three photon process.关键词：upconversion luminescence;YLiF4：Er3+;Tm3+;Yb3+;hydrothermal synthesis103|61|4更新时间：2020-08-11
- 摘要：The plasma display panels(PDPs) are regarded as a medium of large-format panel display.The performance and lifetime of a PDP is strongly related to the nature of phosphor used in it.The working of PDPs is realized by a conversion of vacuum ultraviolet(VUV) to visible light.Therefore,it is important for plasma display panel to improve the properties of the phosphors.Nowadays,the red emitting phosphors(Y,Gd)BO3:Eu3+ for plasma display panels has a poor color purity and the first important thing is searching for a new phosphor with high color quality.In this work,(Y,Gd)(P,V)O4:Eu phosphors was prepared by the conventional solid state reaction method at 1000~1300℃.The structure of prepared sample was checked by X-ray diffraction using Cu-Kα(λ=0.154 nm) radiation at room temperature.The XRD data indicated that the sample is tetragonal,body-centered structure and space group is I41/amd.Spectroscopic properties of the samples were studied in the VUV/UV range.The variation of the luminescent intensity with Eu3+ mol fraction was investigated and the sample with 0.07 Eu3+ has the highest luminous intensity.The emission spectrum of(Y,Gd)(P,V)O4:Eu3+ is composed of several bonds,respectively,centered at 593,611,619,651,676.5,693.5,708.5,713.5 nm.The emission spectrum was dominated by the red peaks at 619 nm due to the electric dipole transition 5D0→7F2,which indicates that Eu3+ occupies a site lacking inversion symmetry.The orange peak at 593 nm was the magnetic dipole transition 5D0→7F1.The excitation spectrum of(Y,Gd)-(P,V)O4:Eu3+ in the VUV range can be divided into two regions,one band centered at 156 nm may be assigned to the absorption of the host,another band centered at 250 nm was the charge transfer transition of Eu3+-O2-.By comparing the spectrum of(Y,Gd)(P,V)O4:Eu3+ with that of(Y,Gd)BO3:Eu3+,(Y,Gd)-(P,V)O4:Eu3+ offers a better chromaticity than that of(Y,Gd)BO3:Eu3+.关键词：VUV;activator Eu3+;chromaticity coordinate;excitation spectrum94|69|3更新时间：2020-08-11
- 摘要：Three types of white-light LEDs consisted of "blue LED chip and YAG phosphor","blue LED chip,YAG phosphor and red phosphor",and "blue LED chip,green phosphor and red phosphor" were fabricated.Their CIE parameters were also mearsued under 20 mA DC driving.The CIE coordinates are (0.326,0.339),(0.326,0.339),and(0.324,0.324);the correlated color temperature Tc are 5781,5627,and 5937 K;and the color-rendering index Ra are 82.3,86.2,and 92.2,respectively.It shows that the adding of red light into the white light will improve the quality of the white light.The different DC driving,increasing of the current from 5.0 mA to 6.0 mA,results in higher color temperature Tc and lower color rendering index.It was found that the red phosphor saturated when the current was higher than 30 mA.The phosphors(M1,M2)10(PO4)6X2(M1=Ca,Sr,Ba;M2=Eu,Mn;X=F,Cl,Br) have been synthesized in reductive atmosphere at 900～1200℃ for 2.0～8.0h.The phosphors with different compositions give the emission at 455,477,500,and 580 nm when excited by 400 nm near UV light.Three types of white LEDs were fabricated using UV LED chips and the phosphors mentioned above.The constitutions are "UV LED chip,blue phosphor,and YAG phosphor","UV LED chip,blue phosphor and red phosphor",and "UV LED chip,blue phosphor,green phosphor and red phosphor".Their CIE coordinates are(0.303,(0.329)),(0.327,0.328),and(0.331,0.333);the correlated color temperature Tc are 7070,5747,(5566) K;and the color-rendering index Ra are 79.2,80.4,and 87.9 under 20 mA DC driving,respectively.The different DC driving,increasing of the current from 5.0 mA to 6.0 mA result in a higher color temperature Tc and a lower color rendering index.However,CIE coordinate of the white light LED consisted of UV LED chip,blue phosphor and YAG phosphor changed the least.关键词：white light LED;rare earth phosphor;CIE coordinate;correlative color temperature;color ren-dering index150|99|10更新时间：2020-08-11
- 摘要：At present,displays,as the medium of people and computer exchange,play an important role.Field emission display(FED) is one of the most promising displays as full color FPD owing to its advantages such as wide view angle,wide temperature range for driving,high picture quality,low power consumption,high response speed,and without magnetic field and X-ray radiation.A lot of obstacles to the success of FED are lack of suitable phosphors,new electron sources for the field emission and encapsulation of FED device.Screens require new luminescent materials and fabricate technology as the one of important segments in FED.It is generally accepted that thin films phosphors have some advantages over bulk-type powder phosphors such as better thermal stability,reduced outgassing,better adhesion,and improved uniformity over the substrate surface.So the research of thin films phosphors becomes a hotspot in the research of FED screen.ZnO:Zn thin films have been grown on ITO substrates by electron beam evaporation method with sintered ZnO:Zn targets,and were annealed in 400℃ and 600℃ respectively.The construction,ingredient,surface morphology and luminescence properties of the ZnO:Zn thin films were performed using X-ray diffraction,(X-ray) photoelectron spectroscope,scanning electron microscope and photoluminescence spectra.The blue/green luminescent peak is detected for the ZnO:Zn thin films.Meanwhile,the singly ionized oxygen vacancies(VO) act as luminescent centers and responsible for the visible luminescence which was strongly affected by the annealing processes.It was found that crystallization is improved,and the disfigurement on crystal surface is repaired with the annealing temperature increase.At the same time,it can be concluded that the width of the main peak in photoluminescence spectra increases after the annealing process.The luminescent properties of ZnO:Zn thin films are enhanced in 400℃ and 600℃ annealing processes.So it can be concluded that post-deposition annealing is one of effective methods to increase luminescence properties of ZnO:Zn phosphor thin films.关键词：heat treatment;ZnO:Zn thin films;electron beam evaporation;field emission display(FED)104|74|3更新时间：2020-08-11
- 摘要：The development of some applications on silicon(Si) substrates has obvious technological advan-(tages),including the low cost,large-scale availability,good thermal and electrical conductivities and the feasibility of removing the Si substrates with wet etching.Significant mismatches in lattice constants and thermal expansion coefficients of silicon and GaN in growth process is encounted,such differences cause crack formation when the thickness of the grown film exceeds a critical thickness.Recently,considerable developments in this field has been achieved,GaN LED grown successfully on Si was reported.Junction temperature is a key parameter of light emitting diode(LED),the junction temperature characteristic of GaN LED on Si substrate is reported firstly.The junction temperature of GaN on Si was measured under forward voltage.This method is based on the dependence of junction temperature on operating voltage.This relationship can be measured and used to compute the semiconductor junction temperatures in response to power dissipation in the junction region.This measurement consists of two steps of measuring: the calibration measurement and the actual junction-temperature measurement.The results showed that the junction temperature of GaN LEDs on Si substrate is different from that on sapphire substrates.The junction temperature on Si substrate is lower than that on sapphire,and the increase speed of the junction temperature is lower on Si substrate than that on sapphire substrate,especially in high operating current.We believe that this phenomena results from the better thermal conductivity of Si substrate than sapphire substrate(the thermal conductivity for Si and sapphire are 5 W/cm·K and 1.5 W/cm·K,respectively).The result that junction temperature is still low in high current suggests that the GaN-base LEDs on Si substrate have much more potential for the application on the high power devices.关键词：Si substrate;GaN;LED;junction temperature120|73|3更新时间：2020-08-11
- 摘要：Due to their wide potential applications in short-wavelength optoelectronic devices,ZnO and it’s alloy have become one of the main topics in the research field of optoelectronic materials and devices.Although high quality ZnO films are available due to the improvement of material growth techniques,the luminescence behavior,mechanism and their relations with the structure of material are still unclear.Much work is needed for further understanding of the optical properties of ZnO films.In this paper,the photoluminescence properties of ZnO film grown by Laser-MBE method have been experimentally investigated.The optical characterization methods we used include temperature-dependent and excitation-intensity-dependent photoluminescence.When using YAG pulse laser as the excitation source,a new emission band appeared on the low energy side,it might be originated from electron-hole-plasma(EHP) recombination.Stimulated emission can be detected both from the surface and the edge of the film,this shows that the film contains certainty quantity of defects.However,the spectrum excited by an Xe lamp under room temperature contains two emission bands: the violet band with a peak at 381 nm and the blue-green band with a peak at 450 nm,based on the information given by the PLE spectrum,a simple model for blue emission in ZnO was proposed.By comparison of the different spectrum using different excitation sources,it is concluded that the violet band emission may require certain high excitation intensity,and the blue band emission saturates rapidly with the increasing excitation intensity.关键词：ZnO film;photoluminescence;EHP;blue band emission117|115|3更新时间：2020-08-11
- 摘要：ZnO materials are very promising for applications in field emission displays and photonic devices operating in blue and UV spectral ranges due to its wide band gap(3.37 eV) and large exciton binding energy(60 meV).Therefore,fabrication and properties of ZnO materials have attracted considerable attention.In this work,arrayed ZnO hexagonal sub-microrods have been synthesized onto glass substrates through a simple two-step chemical solution deposition by altering pH,the concentration of solution and other factors.XRD patterns,SEM images have been measured,which reveals almost of the ZnO microrods were highly orientated on thin films of ZnO template on the glass substrate and grown along the(002) direction.The diameter of the rods is in the range of 200~500 nm and the length of the rods is about several micro-meters.XRD patterns showed that the crystal structure of most of the ZnO sub-microrods is hexagonal structure.The luminescent properties of the ZnO sub-microrods which annealed at 650℃ with different time was investigated by excitation spectrum and photoluminescent spectrum.It revealed the excitation spectra of ZnO sub-microrods have a strong exciton excitation peak at 380 nm,and the blue default emission of the photoluminescent spectra have a blue-shift from 452 nm to 440 nm,the wide orange-red default emission intensity of the photoluminescent spectra become stronger with the peak red-shift from 630 nm to 720 nm with the annealing time increases.The PL spectra of ZnO have a blue peak at 430 nm and a green peak at 505 nm after annealing for 6 h.Compared the calculated data of these intrinsic defects with the theory of FP-LMTO,we attribute the green(505 nm),orange-red(630 nm) and red(720 nm) emission to the transition from oxygen vacancies to the valence band,the blue emission peak at 440 nm to the transition from zinc interserts to the valence band.The enhancement of exciton excitation peak at 380 nm after annealing indicates that the energy transfer from the exciton to the defaultemission center occurred.关键词：ZnO;photoluminescence;microrod;chemical solution deposition111|63|0更新时间：2020-08-11
- 摘要：ZnO is a wide direct band gapⅡ-Ⅵ semiconductor material with a large exciton binding energy of 60 meV at room temperature,more larger than the ionization energy at room temperature(26 meV),so ZnO is a suitable high efficient ultraviolet material.ZnO quantum dots has unique photoelectric properties,especially can be used in UV laser devices related with the exciton characteristic,therefore, it is very important to study the ground state properties of exciton of ZnO quantum dots in theory.We compared the calculation results with the experiment values that indicate the new trial wave function is right.We also calculated the variation parameter Ke and Kh,the normalization constant Ne and Nh as functions of r,and the trial wave function ψ as functions of aB.The results indicate when the radius of the quantum dot is very small(r≤4.0aB),the trial wave function ψ will have a rapid change.And meanwhile the quantum dot will have a larger surface to volume ratio.So the surroundings,the defects and the purities will have strong effects on the ground state properties of the quantum dot,while the medium on the surface(or the interface) will have effects too.Thus,it is very important to reduce the defects and the dangling bonds on surface,eliminate the non-radiative recombination and the surface(the interface) emission by effective doping and modifying.关键词：exciton;ZnO quantum dot;variation method;ground state properties101|70|1更新时间：2020-08-11
- 摘要：A simple and economical method to obtain nano-ZnO films by oxygen-plasma-assisted E-beam eva-poration of metallic Zn onto a Si substrate at 250℃,followed by low-temperature thermal annealing from 300℃ to 500℃ for 1 h in oxygen ambient was described in this paper.The effect of the interface layers between Zn and ZnO on the structural and luminescent properties of the samples was studied employing X-ray diffraction(XRD),Raman scattering and room-temperature photoluminescence(PL) spectra.XRD patterns indicated that the nano-ZnO films had a polycrystalline hexagonal wurtzite structure.The interface mode(Es) centered at about 534 cm-1,which is from the surface of Zn particles coated with ZnO nano-particles.With increasing the annealing temperature,the Es shifted to lower wavenumber with a decrease of intensity.When annealing at 400℃ for 1 h,the Es disappeared,indicating Zn was fully transformed to ZnO.The result of XPS showed the stoichiometric nano-ZnO film was obtained when the sample was annealed at 400℃.Room-temperature PL spectra showed a very strong ultraviolet emission peak at about 381 nm.With increasing the annealing temperature,the intensity of the interface mode decreased.So the bound exciton(from the interface mode) emission decreased and the free exciton emission increased.The film annealed at 400℃ for 1 h had the maximum value of the ratio of UV band to visible emission.All these indicated that stoichiometric,high quality nano-ZnO film was obtained when the sample was annealed at 400℃.关键词：plasma assisted E-beam evaporation;nano-ZnO film;ZnO/Zn interface;photoluminescence110|106|0更新时间：2020-08-11
- 摘要：Ⅱ-Ⅵ family semiconductor nanocrystals(such as CdSe,CdS,ZnS,ZnSe,and so on) have attracted most interests of scientists,recently.The synthesis methods have made great breakthrough in the improving the photo-stability and enhancing the luminescence efficiency during the past decades,of which the most successful way was the preparation of core/shell nanocrystals.However,most of the core/shell systems investigated were single core and single shell systems.The core/shell/shell structural CdSe/CdS/ZnS nanocrystals were synthesized in aqueous solution by using mercapto-acetate acid as stabilizer.The intermediate shell of CdS between the core of CdSe and the outer shell of ZnS could improve the core/shell interface quality as a lattice parameter adaptation layer,and the outer layer of ZnS could confine the exciton to a great extent.The core/shell/shell system combined the advantages of both core/shell systems of CdSe/CdS and CdSe/ZnS in theory.The nanocrystals were characterized by transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS).The TEM image showed that the nanocrystals exhibited sphericity,and the average size was less than 10 nm,and the aggregation occurred among the nanocrystals.The results of XPS confirmed the existence of cadmium,zinc,selenium and sulphur in the core/shell/shell structural samples,which demonstrated the formation of core/shell/shell structural CdSe/CdS/ZnS nanocrystals.The luminescence intensity of different core/shell structural nanocrystals was investigated by using the UV-Vis absorption and photoluminescence(PL) spectra,the results indicated that both of the intensity of absorption spectra and PL spectra of core/shell/shell structural CdSe/CdS/ZnS nanocrystals were the strongest of all,and the red shift was the most distinct of all,which attributed to the surface passivation on the core of CdSe and partial exciton leakage into the shell.By comparison,the results demonstrated that the core/shell/shell structural nanocrystals exhibited the best luminescent properties of all.关键词：core/shell/shell;nanocrystals;luminescent properties;characterization123|116|4更新时间：2020-08-11
- 摘要：Colloidal TiO2 was prepared by hydrolyzation of tetra-n-butyl titanate.The prepared TiO2 powder was heat-treated at 400,600 and 850℃ respectively.The original and the heat-treated TiO2 powder samples were characterized through thermoanalyses(DTA-TG),X-ray diffraction(XRD) and photoluminescence(PL) measurements.DTA-TG and XRD data were used to investigate the structural phase transition and check the crystal types.The XRD data indicated that the original sample and the sample heat-treated at 400℃ were mainly brookite,the sample treated at 600℃ was mainly anatase,and the sample treated at 850℃ was mainly rutile.The DTA-TG data and the XRD data suggested that,as the heat-treatment temperature was elevated,the TiO2 crystals transformed from brookite to anatase and,finally,to rutile and that a first order structural phase transition occurred at 808℃.On the PL spectra of the original powder and the powder samples heat-treated below 600℃,two emission peaks can be observed at 400 nm and 470 nm respectively.The emission at 400 nm could be assigned to the band to band transition.The weaker emission at 470 nm was associated with the surface states of the crystals.With increasing heat-treatment temperature,the size of the TiO2 particles increased,and the interband emission peak at 400 nm shifted to red.In other words,as the size of the TiO2 particles decreased,and the interband emission peak at 470 nm shifted to blue,which arose from the quantum-size effect.As the heat-treatment temperature was elevated to 850℃,the emission peak at 400 nm disappeared,the emission peak at 470 nm became the highest peak,and the emission wavelength range(became) narrower obviously.These phenomena were resulted from the changes of TiO2 crystalline structures.With the increasing heat-treatment temperature,the size of TiO2 crystals increased.As a result,the quantum-size effect became weaker and weaker,and the number of the structural defects became less.Therefore,the photoluminescence of the samples exhibited markedly changes.关键词：titanium dioxide;heat-treatment;structural phase transition;photoluminescence148|109|2更新时间：2020-08-11
- 摘要：Organic light emitting diodes(OLEDs) based on aluminum tris(8-hydroxyquinoline)(Alq3) as an active luminescent material have shown tremendous growth since its inception.Indeed,numerous experiments have provided an insight into mechanisms and processes such as the formation of the metal/organic interface,injection processes,charge transport,the effects of doping,transport,and recombination near organic/organic interfaces.However,even with a relatively good knowledge of these particular processes,it is still not an easy task to predict the properties of a multiplayer organic device without recourse to experiment.We therefore focused our effort on the detailed study of the luminescence characteristics of Alq3-based OLED.The OLEDs with the structure of ITO/TPD/Alq3/LiF/Al were fabricated in the in-line 5-chamber deposition system.The J-V-B characteristics were tested in N2 atmosphere glove-box and in the air using the home-made system.The J-V characteristics in the forward direction,when ITO is positively biased,appears to be trapped-charged limited current(TCLC) which can be described by power laws J∝Vm.The reverse current may be governed by tunneling under high electric field.For low reverse bias,the current may be the leakage caused by pinhole.At high current densities,the brightness-current relationship tends to a linear function.The luminescence efficiency rises as the voltage rising at the low bias voltage region and decrease as the voltage rising at the high bias voltage region.In case of this typical bilayer structure,which is often called "model device",a strong influence of ambient atmosphere on the electrical properties was observed.The J-V characteristics in vacuum exhibited anomalous behaviour,including regions with negative differential resistance(NDR).In air,the anomalous behaviour disappeared.Such J-V characteristics were also observed by other researchers in some OLEDs based on polymers and dye doped Alq3 during the last few years. But no reasonable explanation has been provided for this phenomenon.Especially,the NDR of the "model device" at the low voltage region was not discussed.The test results showed that the negative differential resistance is observed at the voltage of 4 V.Futher analysis indicates that this phenomenon may be attributed to the current filament caused by the pinhole.关键词：organic light emitting diode;luminescence characteristics;negative differential resistanceproperties100|67|0更新时间：2020-08-11
- 摘要：Since Tang et al.developed a very high efficient fluorescent material(Alq3) and made the first OELD in 1987,novel organic electroluminescent materials had attracted much interest.Though developed for ten years more,the performances of 8-hydroxyquinoline metal complexes were more excellent than other organic electroluminescent materials in commerce utilizations,such as good light performance,good thermal stability,and good film formability.Alq3 was the best representation,research on performances and applications of Alq3 has matured.But the research on Znq2 was not enough,which limited the commerce utilizations as an excellent organic electroluminescent material.At this point,some foundation research works were done here.Two Znq2-based organic electroluminescent materials,Znq2(H2O)2 and(Znq2)4,were prepared and characterized by infrared absorption spectrum(IR),X-ray diffraction(XRD),thermogravimetry(TG),differential thermal analysis(DTA),photoluminescence(PL) spectrum and electroluminescence(EL) spectrum.It was shown that the deviating temperature of H2O from Znq2(H2O)2 is 161℃,the decomposing temperature of(Znq2)4 into Znq2 is 361℃,the glass transition temperature of Znq2(H2O)2 is 104.2℃ and that of(Znq2)4 is 204.9℃.In PL spectra,the peak wavelengths of Znq2(H2O)2 and(Znq2)4 are 505 nm and 550 nm respectively.In EL spectra,the peak wavelength of (Znq2)4 is 539 nm.Because of special molecular spatial structure of(Znq2)4,there is an electron tunnel between adjacent(Znq2)4 molecules,which could increase electron transition efficiency from HOMO to LUMO and decrease drive voltage of OELD.The high glass transition temperature of(Znq2)4 could prolong the lifetime of OELD. Above all,(Znq2)4 have great potential in use as organic electroluminescent material.In addition,(Znq2(H2O)2) has great light intensity and narrow FWHM in PL spectra,and it is also a kind of potential(excellent) organic electroluminescent material.Application of(Znq2)4 and Znq2(H2O)2 in OELD will be discussed in detail in future articles.关键词：bis(8-hydroxyquinoline)zinc;Znq2(H2O)2;(Znq2)4;TG;DTA101|55|2更新时间：2020-08-11
- 摘要：A new light emitting material,2(salicylaldehyde with aniline)-(1,10-phenanthroline) calcium was synthesized.Its molecular structure,crystal structure,thermal stability and optical properties were investigated by FTIR spectra,XRD spectra,DSC thermal analysis,UV-vis spectra,fluorescence excitation spectrum and fluorescence spectrum,respectively.Its energy band and light emission mechanism were studied.Results show that 2(salicylaldehyde with aniline)-(1,10-phenanthroline) calcium is a thermally stable,polycrystalline material,whose melting point is about 325℃.In its infrared spectrum,a high intensity band is at about 1650 cm-1.This band is typical of the conjugated C=N stretching vibration,which shift to higher frequency in relation to the free ligand of salicylaldehyde with aniline.A very weak band at 1 248 cm-1 is assigned to(ph-O) stretching vibration,which is weaker than that of the free ligand of salicylaldehyde with aniline.New band at 655 cm-1 is assigned to Ca-O stretching vibration.Its ethanol solution can emits intense blue fluorescence with peak wavelength of 491 nm and its powder also emits intense blue fluorescence with peak wavelength of 449.7 nm under UV irradiation.The redshift of 41.3 nm of fluorescence peak wavelength of 2(salicylaldehyde with aniline)-(1,10-phenanthroline) calcium in ethanol solution relative to its powder state is caused by solvent effect.Its UV absorption bands are at about 222,258,325 and 388 nm,respectively.The absorption bands at about 222 nm and 258 nm are attributed to intrinsic absorption of benzene ring.The absorption band at about 325 nm and 388 nm are assigned to intrinsic absorption of C=N.Its optical gap is about 2.93 eV,which was determined by intrinsic absorption band edge of 2(salicylaldehyde with aniline)-(1,10-phenanthroline) calcium in ethanol solution.Its fluorescence excitation spectrum has two excitation bands located at(361.5 nm) and 409.5 nm,respectively.Its fluorescence originates chiefly from the long wavelength excitation band of 409.5 nm.关键词：2(salicylaldehyde with aniline)-(1;10-phenanthroline)calcium;structure;optical properties105|60|5更新时间：2020-08-11
- 摘要：Microarray technology has provided a way to quantitate the simultaneous expression of a large number of genes.As microarray developed towards miniaturization,high throughput and weak signals,it needs high sensitive and addressable detection.Fluorescent detection has been given more and more attention.The very rapid and remarkable development of fluorescence detection will no doubt impact the applications of microarray technology.In generally,fluorescence intensities of microarrays,which reflect the biochemical reaction are detected by a photomultiplier tube or a CCD camera,resulting in the production of digital images.As microarrays are scanned repeatedly for many times,the fluorescent dye will be bleached and the relative intensities of fluorescence probes will decay,which result in the error of microarray analysis. So the mathematical modification on the values of fluorescence intensities is important during microarray processing.An experimental device based the sensitive CCD area imaging and scanning technology is designed for the research on microarray fluorescence photobleaching properties,which is proved to be useful for fluorescence detection of microarray.The microarray consisting of different concentration fluorescence probes is scanned repeatedly in the same condition by this device,and the relative intensities of the same fluorescence probe in different images are extracted orderly by the special software,and then fitted by the nonlinear curves.The results show that the decay of the relative fluorescence intensity can be fitted perfectly by an exponential fitting method.The meanings of parameters in this exponential model are explained.The relations between the parameters of the exponential model and the concentrations of fluorescence probes are also analyzed.The analysis results can be used to modify the data error caused by the photobleaching in microarray technology and to improve the reliability of microarray analysis.关键词：microarray;photobleaching;fluorescence decay112|100|2更新时间：2020-08-11
- 摘要：With the development of OLEDs,amplified spontaneous emission based on organic/polymer semiconductor materials have attracted a considerable amount of interest.We report the studies on ASE(amplified spontaneous emission) in nematic liquid crystal waveguide doped with DCJTB (2-(1,1-dimethylethyl)-6(2-(2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1-1H,5H-benzo(ij) quinolizin-9-yl)ethenyl)-4H-Pyran-4-ylidene) propanedinitrile) films utilizing a photo-induced distributed feedback(DFB) resonator,which is provided by two-beam interference using Lloyd mirror configuration.It is found that the full width at half maximum of the DFB resonator is much narrower than that of planar waveguide model.The effects of applied electric field on output intensity are also investigated at different observed angles.The output intensity of TE or TM model can be tuned by the external electric field.关键词：amplified spontaneous emission;DCJTB;distributed feedback(DFB);nematic liquid crystal100|225|0更新时间：2020-08-11
- 摘要：Rare earth complexes with organic ligands,such as β-diketone,often show efficient photoluminescence(PL) because of the strong absorption of the organic ligands and efficient energy transfer from the triplet state of ligands to rare earth ions under the excitation of near ultraviolet light.The introduction of anotherlig and and addition of La3+,Y3+ or Gd3+ can considerably enhance the fluorescence intensity of rare earth complexes.In recent years,there has been considerable interest in the luminescence properties of Eu3+ and Tb3+ complexes,but little attention has been paid to the Dy3+ complexes.In this study,three series of solid complexes RExDy1-x(acac)3phen(RE=La,Y,Gd;x= 0,0.10,0.20,0.30,0.50,0.70,0.90,1.00) were obtained by the reaction of acetylacetone(Hacac),1,10-phenanthroline(phen) and mixed rare earth chloride of DyCl3 and RECl3 in 95% CH3CH2OH solution.These complexes were characterized via IR,UV spectra and XRD.The results showed that the two O atoms of acac-and the two N atoms of phen coordinate with RE3+,and these complexes have similar structure.The PL properties of these complexes were also studied.The relation between their PL intensities and the content of doped ions is also discussed.The experimental results showed that the PL intensities of Dy3+ complexes were enhanced after doping La3+,Y3+ or Gd3+.When x is within the range between 0.10 and 0.30,the PL intensities of all doped complexes are stronger than that of the pure Dy3+ complex Dy(acac)3phen.Furthermore,among these three rare earth ions,La3+ is better than Y3+ and Gd3+ in sensitizing the fluorescence of Dy3+.关键词：Dy3+;acetylacetone;ternary complex;dope;photoluminescence property120|56|5更新时间：2020-08-11
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