最新刊期
卷 28 ， 期 6 ， 2007
- 摘要：Taking into account the interaction of an electron with bulk longitudinal-optical(LO) and surface longitudinal-optical(SO) phonons,we studied the effective mass of the bound polaron in a polar slab by using the method of Green's function.The effective mass was derived as function of slab thickness,and it reduces with the increase of the slab thickness;for a very thin slab(d<5 nm),the effective mass was mainly attributed to the electron-SOphonon interaction,oppositely,d>10 nm,the effective mass was mainly attributed to the electron-LO phonon interaction.But when 5nm<d<10 nm,all of them must be consider together.Especially,the effective mass increased when there was the Coulomb potential because the interactions between the electrons and phonons was strengthened.关键词：polar slab;bound polaron;Green's function;effective mass104|94|0更新时间：2020-08-11
- 摘要：With the development of several experimental techniques,for example,metalorgnic 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 is of great interest in investigating quantum dots both theoretically and experimentally.Due to the small structures of QDs,some physical properties such as optical and electron transport characteristic are quite different from those of the bulk materials.The study on the impurity states in these low dimensional structures is an important aspect on which many theoretical and experimental works based.Recently there has been a considerable number of theoretical studies on the effect of a bound magnetopo-laron in a parabolic quantum dot.However,there has very few article on the properties of the internal excited state of bound magnetopolaron by using the linear combination operator in parabolic quantum dot up to date.In this paper,by using the linear combination operator and the unitary transformation method,the properties of the excited state of the weak-coupling bound magnetopolaron in a parabolic quantum dot were calculated.The relation of the vibrational frequency,the first internal excited state energy,the excitation energy and the resonance frequency of the weak-coupling bound magnetopolaron with the effective confinement length of the quantum dot,the Coulomb bound potential,the electron-LO-phonon coupling strength and the cyclotron frequency in a parabolic quantum dot were obtained.Results show that he vibrational frequency,the first internal excited state energy,the excitation energy and the resonance frequency of the bound magnetopolaron increase rapidly with decreasing the effective confinement length in the electron-phonon weak-coupling case in a parabolic quantum dot.They also increase with increasing the Coulomb bound potential and decreasing the electron-phonon coupling strength.关键词：parabolic quantum dot;weak-coupling bound magnetopolaron;effective confinement length;the first internal excited state energy106|54|0更新时间：2020-08-11
- 摘要：Based on model of Huybrechts strong-coupling polaron,the ground state energy of the system,in which the excitons interact with both the weak-coupling bulk longitudinal-optical(LO) phonons and strong-coupling interface-optical(IO) phonons in a polar crystal,is studied by using the Lee-Low-Pines variational method,the self-trapping energy and the induced potential of the excitons are derived.The results are shown as following:1.The self-trapping energy of the excitons is composed of two parts.One part is the polaron effects resulting from the exciton-LO phonon interaction,the other part is induced by the exciton-IO phonon interaction.The self-trapping energy Ee,h-LOtr,which is produced by the interaction between the exciton and LO-phonon,will increase with increasing the coordinate z,it tends to a constant finally.The self-trapping energy Ee,h-IOtr,which is induced by the interaction between the exciton and IO-phonon,will increase with decreasing the coordinate,especially near the interface,the decrease in z will lead to drastic increase in Ee,h-IOtr.It is indicated that near the interface,the contribution of the electron-IO phonon interaction to the self-trapping energy of the excitons is dominant,whereas the exciton in the bulk far from the interface,the contribution of the electron-LO phonon interaction to the self-trapping energy of exciton is dominant.The influence of the distance ρ between the electron and hole on the self-trapping energy Ee,h-IOtris also remarkable.Ee,h-IOtr will increase with increasing ρ.With ρ increasing,the decrease in coordinate z will lead to drastic increase in Ee,h-IOtr.2.The induced potential of the excitons is also composed of two parts,one part is the polaron effects produced by the interaction between the exciton and LO phonons,the other part is induced by the exciton-IOphonon interaction.The variation law of the induced potential Ve,h-LO and Ve,h-IO resulting from the exciton-LO phonon and exciton-IO phonon interaction,respectively,is agreement with the variation law of the induced potential produced by the weak-coupling exciton-LO phonon interaction in 3D polar crystal and the strong-coupling exciton-SO phonon interaction in 2D polar crystal respectively.The influence of the coordinate of the exciton on the induced potential Ve,h-IO and Ve,h-IO is notable.Ve,h-LO increases with increasing the coordinate z.With z increasing,the increase in the distance ρ between the electron and hole will lead to drastic decrease in Ve,h-LO.The induced potential Ve,h-IO decreases with increasing z.With z decreasing,the decrease in ρ will lead to drastic increase in induced potential Ve,h-IO.The results show that the influence of the surface and interface phonon in polar crystal can not be neglected.It is especially important for the polar slab,quantum well and heterostructures,in which the carriers are both strong-coupling with surface or interface optical phonon and weak-coupling with bulk longitudinal optical phonon.关键词：exciton;strong-coupling;self-trapping energy;induced potential101|85|0更新时间：2020-08-11
- 摘要：Aquantum dot(QD) consists of an artificial structure in which electrons are confined in all three spatial dimensions and thus has a fully quantized energy spectrum.Aset of electrons held in such a structure is similar to a set of atomic electrons bound to a nucleus,and for this reason QDs are sometimes termed "artificial atoms".Optical and electric properties of QDs structures recently have attracted much attention because of their application potential.These properties are closely related to excitonic states and their coupling with optical phonon modes.There has been a considerable amount of work on the properties of excitons in different QD structures experimentally and theoreti-cally.The purpose of the present work is to investigate the polaron effects on the magneto-exciton in assembled QDs,and to describe a calculation of the Coulomb interaction with a simple perturbation theory.It was shown that,the interaction of the charged particles with bulk longitudinal optical phonons(LO-phonons) is primary and first important.So in this work we restrict ourselves to examine the interaction of electron and hole with bulk LO-phonons only.We write down the Hamiltonian of the exciton-phonon system in QDs with an external magnetic field,and obtain the energy levels of the system by using a developed LLPmethod.The results show that the polaron effects on the magneto-exciton are to lower the energy levels,but the decrements are small.关键词：exciton;quantum dot;magnetic field121|81|1更新时间：2020-08-11
- 摘要：In the early 1980's,Tokuda investigated the mean number of phonons in the cloud around the electron for both the optical and the piezoelectric polarons within the scheme of variational approach based on the unitary transformation and the method of a Lagrange multiplier.The properties of the mean number of phonons of magnetopolaron are investigated by many investigators using many other methods.The properties of the mean number of phonons of the magnetopolaron in a surface of crystals and quantum wire have been studied using the linear-combination operator and unitary transformation method by one of the present authors and co-worker.Recently,the properties of the mean number of phonons of the magnetopolaron and the bound magneto-polaron in a symmetric quantum dot have been investigated using the linear-combination operator and the variational method of Pekar type method by one of the present authors and a co-worker.However,using a linear-combination operator method,the properties of the mean number of phonons for magnetopolaron in an asymmetric quantum dot have not been investigated so far.In this paper,the influences the asymmetric parabolic confined potential on the properties of the mean number of phonons for the magnetopolaron in quantum dot were studied by using a linear-combination operator and unitary transformation method.The relations between the mean number of phonons and the vibrational frequency of the strong-and weak-coupling magnetopolaron in an asymmetric quantum dot with the transverse and longitudinal direction confinement strength of the quantum dot and the electron-phonon coupling strength are derived.Numerical calculations on the RbCl crystal,as an example,were performed,and the results show that the mean number of phonons and the vibrational frequency of the strong-coupling polaron will increase strongly with increasing the transverse direction and longitudinal direction confinement strength of the quantum dot,and will increase with increasing the electron-phonon coupling strength.关键词：asymmetric quantum dot;mean number of phonons;magnetopolaron99|73|1更新时间：2020-08-11
- 摘要：Organic light emitting diodes(OLEDs) have been attracting a lot of attention because of its potential application in flat panel displays(FPD).In the past two decades since efficient double-layer OLEDs was first reported by C W Tang et al.,tremendous progress has been made in device fabrication and performance optimization,highly efficient and colorful devices have already been fabricated for commercial use.Almost all giants in display around the world,e.g.,Samsung,Sony and Philips,were involved in developing OLEDs for the next generation of FPD.Some people even estimate that OLEDs will replace liquid crystal displays(LCDs) in the next decade.However,there still remain some fundamental mechanisms of devices for scientists to deal with,such as long-term stability of organic materials or device,transportation and recombination of carriers,energy transferring process.In addition,finding a simple fabricating way to realize full-color OLEDs is also an important and imperative approach to reduce manufacturing cost in industrial production.As a promising technology for flat panel display,OLEDs have attracted a great deal of attention since 1987.During the past few years,remarkable progress has been made in the development of multicolor and full-color OLED displays.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-electron forming the exciton,and light emission through the radiative recombination of excitons.The influence of bias voltage on the charge carrier recombination zone of doping organic light-emitting diodes(OLEDs) with the ELspectra improvement of red dopant 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran(DCJTB) doped into tris-(8-hydroxylquinoline)aluminum(Alq3) host material has been investigated,and different doping effect of host material Alq3and N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine(NPB) through studying the electroluminescence(EL) spectra and photoluminescence(PL) spectra was discussed.The results showed that charge carrier recombination zone moved to hole transport layer with increasing bias voltage and optimum host material should have higher energy transfer efficiency and lower charge carrier quenching property.关键词：organic light-emitting diodes(OLEDs);charge carrier recombination zone;bias voltage;host material118|73|1更新时间：2020-08-11
- 摘要：Organic light-emitting diodes (OLEDs) with a top-emitting configuration have been widely studied since they can realize high-performance active matrix flat panel display with integration of thin-film transistors within the substrates.Top-emitting OLEDs are generally composed of a reflective bottom anode,organic layers,and a semi-transparent top cathode for light out-coupling.The modification of the bottom anodes is essential for achieving high light-emitting efficiency.Here,efficient top-emitting OLEDs are fabricated with a structure of Al/Ag with O2-plasma modification/NPB (35 nm)/Alq3(40 nm)/Sm(25 nm)/Alq3(50 nm),where N,N'-di (naphthalene-1-yl)-N,N'-diphenyl-benzidine (NPB) and tris(8-hydroxyquinolinato) aluminum (Alq3) are used as a hole-transport layer and an electron-transport/emissive layer,respectively.The metals of silver(Ag) and samarium(Sm) are used as the reflective anode and the semitransparent cathode,respectively.Alayer of Alq3overlaid on Sm aims at enhancing light out-coupling efficiency and preventing Sm from oxidation rapidly.The Ag anode is subjected to O2-plasma treatment before depositing organic layers.The ultraviolet photoelectron spectroscopy (UPS) analysis shows that the hole injection barrier at Ag/NPB interface is effectively reduced from 1.43 to 1.10 eV by O2-plasma treatment.The influence of the O2-plasma treatment time on the device performance is also studied.The device performance of the top-emitting OLEDs is remar-kably enhanced by using Ag anode with O2-plasma modification.Amaximum current efficiency of 6.14 cd/Ais achieved at an optimal treating time of 60 s.关键词：organic electroluminescence;top-emitting;injection barrier;O2plasma122|105|0更新时间：2020-08-11
- 摘要：The development of flat panel display devices such as field emission displays (FEDs) and vacuum fluorescent displays (VFDs) requires highly efficient cathodoluminescent materials.While many efficient sulfide-based phosphors have been explored as possible low-voltage phosphors,the volatility of sulfur has prohibited their use in FEDs or VFDs.Sulfide-base phosphors often degrade under high energy electron bombardment due to dissociation of the cation-sulfur bonds.Oxide phosphors offer potential advantage because of their superior stability under electron bombardment and excellent luminescent properties.SrGa2O4 is an attractive oxide phosphor for low-voltage cathodoluminscence applications in VFDs and FEDs.Like other wide bandgap semiconductors,SrGa2O4exhibits a purple emission.Activation with Eu3+ ions,the emission shifts to red.The Eu3+doped SrGa2O4phosphor was prepared with the conventional solid-state reaction method.The phase composition was characterized by powder X-ray diffraction.The result shows that the producing powder belongs to monoclinic crystal system with its lattice constants:a=0.943 nm,b=0.900 nm,c=0.839 nm,β=89.06°,and with space group P21/c(No.14).The excitation and emission spectra were measured.The main peak at 610 nm can be ascribed to the electric dipole transition5D0→7F2,which indicates that Eu3+occupies a site lacking inversion symmetry.The peaks at 590,610 nm transition emission split to two peaks:5D0→7F1(586,597 nm) and 5D0→7F2(609,615 nm),respectively,due to the crystal-field in the conditions of mole fraction of Eu3+with more than 1%.The strength ratio of two parts for the splitting peak7F2 can be changed according to the concentration of Eu3+.关键词：SrGa2O4;luminescence;energy level splitting100|64|2更新时间：2020-08-11
- 摘要：The luminescence properties of Ce3+ions in yttrium aluminum garnet(YAG) powder have been studied.The addition of 5% NH4F flux is equivalent to decrease the preparation temperature by 200℃.Since the ionic radius of Ce3+(0.1283 nm) is a little larger than that of Y3+(0.11159 nm),one can expect that Ce3+ experiences a strong crystal field in YAG:Ce.If all the added Ce3+ ions enter into the crystal lattice,substitute the sites of Y3+ ions,and then are incorporated as Ce3+at undisturbed Y3+ sites,the reagent need to absorb plentiful Joule heat.The content of cerium determines the preparation temperature,more cerium means higher preparation temperature.We consider that the NH4Fflux has no effect on the growth of YAG:Ce crystallite because of its low melting point.In order to improve the fluorescence intensity of green-yellow-emitting phosphor based on YAG:Ce for white LED(light-emitting diode),the effect of BaF2 and MgF2 as charge compensators were studied separa-tely.But the charge compensating mechanism has seldom been reported before.When the charge compensator and NH4F were jointly added,the intensity of emission was enhanced.When the charge compensator is MgF2,the intensity of phosphor YAG:Ce has the strongest brightness.The photoluminescence intensities of YAG:Ce phosphor particles with Ba2+,Mg2+ doped were about 135%~142% of that of YAG:Ce phosphor particles without charge compensator.This result can be explained in terms of the environment of trivalent cerium in the crystal structure of YAG.On one hand,we postulate that the oxygen vacancy formed upon calcining in a reductive atmosphere is the most important intrinsic defect.Acompensation mechanism expected for YAG:Ce with Mg2+ codoped is provided by the association of two Mg2+ ions with an oxygen vacancy.In this case,the introduction of Mg2+ ions in YAG:Ce takes place in accordance with the scheme:This scheme implies that at certain cerium concentrations a single oxygen vacancy can be compensated by two Mg2+ ions.On the other hand,Ce3+ and MgF2 dopants have counteracting effects on the lattice parameter of cubic YAG.Ce3+ ions,which replace Y3+of YAGto form a substitutional solid solution,cause an increase in the lattice parameter as the ionic radius of Ce3+is larger than that of Y3+,while Mg2+ ions leads to a decrease in the lattice parameter because the ionic radius of Mg2+(0.086 nm) is smaller than that of Y3+.Further more,Mg2+ can substitute Y3+ easily without disturbing the crystal lattice.The addition of BaF2 as charge compensator acts as the role of MgF2.Differently,Ce3+and BaF2 dopants don't have counteracting effects on the lattice parameter of cubic YAG (the ionic radius of Ba2+ is 0.135 nm,larger than Ce3+and Y3+).The lattice parameter expands because of a repulsive interaction between cations.The effect of doping on the optical behavior of YAG is even more complex.To analyze the role of charge compensator on the luminescent emission property of YAG:Ce,the synthesized products were characterized by XRD,photoluminescence emission and excitation spectra (PLE).关键词：YAG:Ce;flux;charge compensators;photoluminescence160|106|4更新时间：2020-08-11
- 摘要：The Zn1-xMnxO(x=0.07) thin films were grown on glass by direct current(dc) magnetron sputtering,and the influences of oxygen partial pressure on crystallization behavior as well as on optical properties of Zn1-xMnxO films were investigated.X-ray diffraction(XRD) results indicate that the films are highly c-axis oriented,especially at the ambient of oxygen partial pressure of 0.4.When Ris 0.4,there are the smallest full width at half maximum(FWHM) of the diffraction peak and the biggest grain size.The lattice parameter c of the Zn1-xMnxO thin films is larger than that of ZnO film.The optical transmission spectra show that the absorption is the largest when Ris 0.4.X-ray photoelectron spectroscopy(XPS) results show:1.the two peaks at 640.7 and 652.3 eVare in agreement with the binding energy of Mn 2p3/2and Mn 2p1/2without other XPS signals,indicating the coexistence of small amounts of Mn2+and MnO2. 2.the binding energy of Zn 2p3/2is 1021.7 eVwith a narrow linewidth of 1.86 eV,implying only a single component of Zn2+ions. 3.the two narrow peaks at 530.1 and 532.0 eV,the former may be attributed to O2-ions in Zn-O and Mn-O bonds,while another is associated with the loosely bound oxygen chemisorbed on the surface and/or grain boundary of polycrystalline film.The quantitative analysis indicates that the atom fraction of Mn doped in film is 7.3%(Zn0.93Mn0.07O).Owing to Burstein-Moss(B-M) effect,the absorption spectra show that the blue-shift absorption edge transition happens between valence band level and near or above the Fermi level,while the absorption band tailing is attributed to the d-d transitions of tetrahedral Mn2+ between the crystal-field-split 3d5multiplet levels.When x is sure,the band-gap energy is the largest at Rbeing0.4by calculation.It can be interpreted when the alloy enters the antiferromagnetic or spin-glass phase,the effect of the exchange interaction decreases,in turn removing this red shift,and producing an apparent additional blue shift of the energy gap at low temperatures and oxygen partial pressure below 0.4.关键词：Mn-doped ZnO thin films;sputtering;optical properties123|98|1更新时间：2020-08-11
- 摘要：Zinc oxide(ZnO) in nanostructure has the feature to adsorb great amount of gas in order to form a certain kind of surface state.The electronic conductivity of ZnO nanorod experiences a considerable change during the process of adsorption.In this work,gas sensor was fabricated from ZnO nanorod arrays prepared via a facile hydrothermal decomposition on Indium Tin Oxide(ITO) glass.The ZnO nanorods show very good crystalline characterized by Scanning Electronic Microscopy(SEM),X-Ray Diffraction and High Resolution Transmission Electronic Microscopy(HRTEM).It was found that the sensor show sensitive response to the introduction of CO of 1.25 mg/Lat 200℃ with a sensitivity factor(S) of 18.It would be desirable that even better sensitivity be achieved by means of enhancement of the ZnOcrystalline structure and improvement of the surface reaction efficiency.More importantly,this is a simple cheap approach to manufacture gas sensors with nice environment-friendly.It would probably turn out to be an economic way to produce gas sensors in a large scale with low cost to meet the industrial requirements.关键词：hydrothermal method;zinc oxide;gas sensor157|98|3更新时间：2020-08-11
- 摘要：Superluminescent light emitting diode(SLD) is a kind of semiconductor light source with high performance comparing to those of laser diode and light emitting diode.One of the key device in fibre optic gyroscope systems is a superluminescent diode(SLD).In this paper,non-uniform well-thickness multi-quantum wells structure was adopted to widen the output spectrum of superluminescent diode.The epitaxial material was fabricated by molecular beam epitaxy(MBE) technique.Optical and structural characteristic of the film was studied by photoluminescence(PL) at different temperature,X-ray double crystal diffraction and electroche-mical C-Vprofiling method.The radition wavelength of 844 nm was obtained on PLspectrum(300 K).The experimental results of X-ray double crystal rocking curve and low temperature(10~300 K) PLshow that the structure designed for superluminescent diode have been realized.The spectral FWHM over 26 nm,CW output power of over 6 mWhave been achieved at operating current of 140 mA.关键词：superluminescent diodes(SLDs);non-uniform well-thickness multi-quantum wells;photoluminescence113|98|1更新时间：2020-08-11
- 摘要：White light-emitting-diodes(LEDs) are known as a new generation lighting source.The luminous flux,color temperature and color rendering property are the three main index in light source.Using a blue LED with a phosphor layer which is excited by blue light and down-converting to the second light,such as yellow light,white light can be produced.Now white-LED is a hot-spot of research,the point of designing white-LED used for lighting is its colour temperature and efficience,and the phosphor layer in white-LED is very important to this.The placement of the phosphor,the geometry of the encapsulation dome,and the reflector cup influence on the optical loss,and hence on the device efficiency.We can find the energy loss term in the one-dimensional model and observe the phosphor layer thickness and boundary effect.Finally we can optimize the phosphor-type white LEDpackage to obtain higher light extraction efficiency.Recently,it has been demonstrated that a large separation between the phosphor and the primary LED emitter,which we refer to as remote phosphor arrangement,enhances the phosphorescence extraction by reducing the optical power absorbed by the LED chip.The experimental enhancement of phosphor efficiency is 24% for blue-pumped yellow phosphor at 20 mAforward current.This improvement is mainly due to the reason:the phosphor-on-top arrangement reduces absorption of phosphorescence the LED chip.it is not known what will happen to the yellow light when it strikes the phosphor medium.To the best of our knowledge,there are no past studies that have quantified the transmission and reflection properties of light outside the excitation wavelength region of YAG:Ce phosphor.By analysing,the color coordinate,color temperature,Luminous flus,Lumen efficiency varied with forward current.From the result of the experiment,we know that color coordinate x and y is minish varing slowly with the increasing forward cureent.The color coordinate and the color temperature is the same uptrend.The luminous flux increases with increasing forward current,but the lumen efficiency decreases with increasing the forward current.关键词：W-LED;color coodinate;color temperature;luminous flux;lumen efficiency158|153|9更新时间：2020-08-11
- 摘要：Laser diode array can operate with high quantum efficiency,output wavelength can range from 570 nm to 1600 nm,and hours of work can be even longer than mega hours.Multi-array stack of Laser Diode Arrays(LDAs) can supply ultrahigh power laser beam and are becoming widespread sources for many kinds of applications involving regions of industries,medicine etc.However,a free-running LDAs always operate on a wide bandwidth with the poor coherence,the laser beam cannot be focused to a small spot with a well-defined intensity profile,and the requirements of high quality laser applications can not be met.So external quarter-Talbot cavity is employed for phase-locking,but corresponding supermode is the out-of-phase supermode,and among all supermodes,only the far-field of the fundamental supermode is central single-lobe,the output is near diffraction-limited,the angle of divergence is the smallest,the concentration of light beam is the greatest,the laser spectrum is the narrowest,thus it is necessary for the external mirror to be tilted by an angle of β=λ/2d,here,λ is the operating wavelength,and d is the period distance,this makes feedback light from array lasing in the fundamental supermode be imaged dominantly in lasing aperture but makes the others be imaged exactly in between lasing apertures,thus only the fundamental supermode be allowed oscillating,but if the output power of a LDAs is ultra high,after it emits a short time,though there is cooling subsystem,so the LDAs can operate continuously,induced by the residual thermal radiation etc,the external mirror will be deformed stochastically to make β drift off λ/2d,with the output power increasing,the margin will up to the cri-tical value,the tilt in degree will mismatch the fundamental supermode,feedback light from array lasing in the fundamental supermode won't be imaged dominantly in lasing aperture,this result in LDAs allowing the other supermode oscillating,the far field distribution will be not single-lobe far field pattern any longer,quality of the output laser beam will be lowered severely,therefore the stability analysis of ultrahigh power LDAs phase-locking with tilted external cavity and corresponding law of change have been specially done at first,then the novel self-adaption two-control technology can be and has been specially developed,with fitting sensor detecting source,matched lens array and so forth in the specially designed structure,the sensing subsystem can effectively detect the deformation of the external mirror in time,and the mating regulating subsystem will compensate the margin concurrently,feedback light from array lasing in the fundamental supermode will be imaged dominantly in lasing aperture stably.The experiment demonstrates that working parameters of a ultra high power LDAs with tilted external cavity is stable by realizing the proposed technology,quality of the output beam from the LDAs is guaranteed high,the performance of the LDAs is improved,so the LDAs can be adequate to satisfy requirements of high quality laser applications,this is significant for ultra high power LDAs applications.关键词：ultra high-power laser diode arrays;the fundamental supermode;external quarter-Talbot cavity;deformation;self-adaption two-control stabilization104|84|0更新时间：2020-08-11
- 摘要：The passivation of (100)GaAs surface was investigated by Na2S,(NH4)2S and CH3CSNH2 solution to find optimal passivation methods.(NH4)2S+ t-C4H9OH,CH3CSNH2+NH4OH and CH3CSNH2+t-C4H9OH sulf-solutions have been used for passivation comparation of(100) GaAs surface by means of Ar+ laser excitated photoluminescence(PL).The relative PLspectrum intensity of sample treated by (NH4)2S+ t-C4H9OH passivation is 10 times stronger than that of unpassivated samples.The results indicate that(NH4)2S+ t-C4H9OH solution has the better passivation effect on(100) GaAs surface.关键词：GaAs;surface passivation;photoluminescence;non-radiation recombination100|86|0更新时间：2020-08-11
- 摘要：The CdSe/ZnSe asymmetric quantum wells sample were grown on GaAs substrates by MOCVD.The samples consist of a 112 nm ZnSe buffer layer followed by two 22ML and a 10MLs CdSe quantum wells and then a 51 nm ZnSe cap layer.The ZnSe barriers between the quantum wells are 34 nm and 3.9 nm,respectively.Asingle quantum wells was also prepared as a comparison with the asymmetric quantum wells.It contains three 10ML CdSe quantum wells separated by a 34 nm ZnSe barrier and it was fabricated at the same condition with the asymmetric quantum wells.Spontaneous emission has been studied in the CdSe/ZnSe asymmetric quantum wells.There are two emission peaks of the photoluminescence spectra of the sample corresponding to n=1 heavy hole exciton recombination from the wide well (WW) and narrow well (NW) in the temperature range of 82 to 141 K,respectively.The emission peak of the NW can not be seen after 141 Kand is identified by the spontaneous emission spectrum of the single quantum wells at 82 K.The exciton recombination both in the NW and WW is influenced by two factors:the exciton tunneling and the thermal dissociation processes.For the WW,the influences on the emission intensity of two factors are contrary.The change of the emission intensity in the WW is determined by the stronger one:the exciton tunneling plays the more important role in the temperature ranging from 82 Kto 141 Kand the thermal dissociation processes play the more important role for the rest of the temperature.For stimulated emission of the CdSe/ZnSe asymmetric quantum wells,owing to the difference of the energy levels between the WW and the NW,the carriers tunnel from the NW to the WW,which can influence the emission effectively.Space charges caused by different tunneling rate between electrons and holes lead to the formation of the internal electric field which affects carriers tunneling.As the result of the internal electric field effect,the changing of the electrons density excited with excitation intensity is super-linear.The carrier which decides the changing of the peak energy in the wide well is exciton which comes from two sources,one is excited by photon in the wide well,and the other one is that tunneling from the narrow well.关键词：asymmetric quantum wells;exciton tunneling;photoluminescence109|56|0更新时间：2020-08-11
- 摘要：Optical absorption analysis is one of the most important technologies for understanding the microstructure of thin films and their band gap properties.For silicon nanostructures,the traditional Tauc method that succeeded in amorphous material is not applicable since the optical absorption of silicon nanostructures would be affected not only by the quantum confinement effect of nanoparticals in the films but also by their concomitant microstructural disorder.In this paper,an optical absorption model for the silicon nitride thin films embedded with amorphous silicon nanoparticles(a-Si NPs/SiNx) is proposed based on quantum confinement effect assuming that a-Si NPs acts a system of three-dimensional confinement quantum dots with a size distribution and the silicon nitride matrix provide a potential barrier.The optical absorption of the films is mainly determined by optical excitation in the system of a-Si NPs.Through simulating the optical absorption spectra of the a-Si NPs/SiNx thin films with above model,we have obtained the size distribution of a-Si NPs and the mean optical gap of the thin films.The effect of surface structural disorder of the a-Si NPs on the optical absorption of the films is also discussed based on the Infrared optical absorption analysis.Agood agreement between the simulated optical absorptions and the experiment results has been obtained in high energy region.Whereas,the deviation of simulated optical absorptions from experiment results in low energy region shows an increased trend.The results show that the quantum confinement effect of a-Si NPs determines the optical absorption of the thin films in high-energy region and the increase of the optical gap is correlated to the decrease of the mean size of the nanoparticles with increasing nitrogen contents.The optical absorption in the low-energy region is mainly generated from the optical excitation in the sub-band states that related to structural disorder and their enhancement in intensity with increasing nitrogen contents can be accounted by the increase of the portion of small a-Si NPs in the films.关键词：amorphous silicon nanoparticles;quantum confinement effect;structure disorder113|86|1更新时间：2020-08-11
- 摘要：Nano ZnO was a kind of fluorescence materials with high exciton binding energy and wide direct gap.But as the red fluorescence materials,it needed to be improved such as luminescent efficiency and color purity.It can be solved effectively by doping extraneous ingredients.Most methods of preparing nano-ZnO were complex and high energy consume.The aim of this article is to find a kind of green synthesis method of nano-ZnO with high luminescent efficiency and color purity.The red fluorescence powders were obtained by doping Eu ion because of its narrow band emission character,so it can be easily industrialized.The samples were prepared by finely grinding and mixing Eu(NO3)·6H2O and Zn(CH3COO)2·2H2Oin an agate mortar.Via mechanical solid-phase reaction,chemical reactions and physical processes were accelerated between reactants.So precursors powder were obtained with less granularity,and nano-ZnO:Eu3+powders were prepared by mixed precursors decomposing at 900℃.The characteristics of samples were investigated by means of TG-DSC,XRD,SEM,TEM.Results showed that the obtained powder exhibits a normal size distribution,whose size is about 80 nm.while the maximum emission spectra peak is at λem=615 nm with 465 nm excitation,corresponding to5D0→7F2transition.关键词：mechanochemstry;nanoscale materials;ZnO:Eu;fluorescence117|103|3更新时间：2020-08-11
- 摘要：Among functional dyes,perylene diimides have been of great interest due to their unique optical and photophysical properties.But the manipulation of superlong1Dstructure of perylene diimides,however,is still a challenge.In this paper,superlong microfiber of bis(n-butyl) substituted perylene diimide(1) has been obtained by solvent evaporation method.FESEM and TEM micrographs indicate that the microfibers are 1~2 μm wide and several hundred micrometers long.XRD measurement demonstrates that the walls of the microfiber are arranged in highly ordered nanoscopic structure.Driving force for the formation of microfiber has been proposed,i.e.,cooperation of solvophobic effect for molecules(1) and π-π stacking interaction between the perylene diimide cores.The effect of the closely packed structure on its photophysical behavior is demonstrated by the UV-Vis absorption and fluorescence spectra.关键词：perylene diimide;microfiber;self-assembly;photophysical properties113|56|0更新时间：2020-08-11
- 摘要：The novel ternary solid complex of rare earth neodymium(Nd) with oxalic acid(OA) and acroleic acid(AA) was synthesized.The chemical structure and the properties of the complex were characterized by using the element analysis,FT-IR,UV-Vis spectrum,thermal gravimetric analysis (TGA) and fluorescence spectrum.Their composition was determined to be [Nd(OOC-COO)(CH2CH-COO)]·3H2O.The TGA result showed that the complex has excellent thermal stability.The fluorescence spectrum suggested that the innovative complex containing rare-earth ions(Nd3+),with strong characteristic emissions due to the4G5/2+2G7/2-4I9/2transition of Nd3+ions,is a kind of photoluminescence materials.关键词：rare-earth;complex;fluorescence spectra105|94|1更新时间：2020-08-11
- 摘要：Eu(BA)3was assemblied into the channels of MCM-41 directly,then the organic-inorganic hybrid material Eu(BA)3-MCM-41 was gained,and the products were characterized by small angle XRD,IR and excitation-emission spectra.The results indicate that the assembly have more ordered mesoporous structure than MCM-41.Eu(BA)3can act as a secondary template when it enters the channel and increase the ordered framework of mesoporous silicon.The assembly keeps some typical absorption band of MCM-41,but the disappearance of the absorption peak at the wavenumber of 3451,1642 cm-1and the intensity decrease of the absorption peak at 970 cm-1in the assembly show that the water adsorbed and the hydroxyl in MCM-41 are reduced by the entrance of Eu(BA)3.Eu(BA)3can be bonded with the hydroxyl in the channel,thus the vibration energy of hydroxyl is reduced,then the luminescence of Eu3+is enhanced effectively.Eu(BA)3has a stronger absorption of the excitated light in the assembly since MCM-41 was used as a host for Eu(BA)3,and there is strong effect between the host and the guest.The assembly mainly exhibits the fluorescence of Eu(BA)3,but the luminescence of MCM-41 does not appear.It is due to the fact that Eu(BA)3can be incorporated with MCM-41 in the assembly,where the latter transfers the energy absorded to the former,and the luminescence of the guest is highly strengthened.The weak emission peak at 588.3,593.3 nm in Eu(BA)3-MCM-41 are formed by the split of the emission peak at 591.3 nm of Eu(BA)3,which is attributed to the transition of5D0→7F1 of Eu3+.The relative luminescent intensity of the peak at 610.2 nm which belongs to the transition of5D0→7F2 of Eu3+is up to 299 times more than that of Eu(BA)3.So it confirms that Eu(BA)3-MCM-41 has an excellent luminescence properties.关键词：mesoporous material;MCM-41;Eu(BA)3;organic-inorganic hybrid;luminescence93|68|3更新时间：2020-08-11
- 摘要：The interaction of protein with solid surface is not only a fundamental phenomenon but also the key to several applications improtantly and novelly.The immobilization of functional proteins to a solid support is greatly important for biosensors and biochips.In this work,FITC labeled antibody was covalently immobilized on silicon surfaces modified by 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde.The fluorescence spectra of absorption and covalent immobilization FITC labeled antibody was investigated.Subsequently,immobilizing human IgGbound FITC-goat anti-human IgG fluorescence immunoassay were obtained.The results showed that the fluorescence intensity of FITC labeled antibody on covalently immobilized surface was 6 times lager than that on absorption surface.9 nm and 4 nm red-shift at the peak of FITC fluorescence was observed on covalently immobilized surface and adsorption surface,respectively.But 3~4 nm red-shift at the peak of FITC fluorescence was obtained in the fluorescence immunoassay.Finaly,stability of covalently immobilized antibody was studied.The results indicated covalently immobilized antibodies larger than absorbed antibodies on fiber optic surface.And the interaction between immobilizing FITC-labeled antibody and fiber optic surface on covalently immobilization fiber optic surface stronger than that on absorption fiber optic surface.Combining this antibody covalent immobilization methods and the fluorescence spectroscopy analysis technology has the potential to be developed into the fast and simple fluorescence immunoassay and fluorescence multilabelling detection for biosensor.关键词：optical fiber biosensor;covalent immobilization and physisorption;fluorescence spectrum111|70|1更新时间：2020-08-11
- 摘要：The effects of Mn2(CO)10compound on DNAhave been studied by the UV-Vis and fluorescence methods.The possible active ways of these complexes with DNA have been discussed.The absorption of EB-DNA system in the presence of Mn2(CO)10showed that Mn2(CO)10could partly sustain the place of EB.The result of fluorescence spectra suggested that Mn2(CO)10could make the fluorescence intensity of DNA increase sharply.All the experimental results show that Mn2(CO)10cluster interacts with DNAin the mode of intercalation.关键词：Mn2CO)10;DNA;UV absorption spectra;fluorescence spectra;intercalative binding mode96|92|0更新时间：2020-08-11
- 摘要：Aiming at the measurement of the cow bloods,the generation mechanism and characteristic of fluorescent spectra of cow blood were researched in this paper.The fluorescent excitation and spectrum measurement system is fluorescence spectrophotometer RF-5301 (Shimadzu).The experimental sample was the normal blood that was drawn out from the cow vein.When added into some anti-coagulator,the blood samples' spectra were measured.These experimental cows were selected from the several farms in the province of Heilongjiang.They were all healthy cows but different in age.The experiment results show that the fluorescence of the cow bloods can be effectively induced by light wave.The intensity and peak value of the fluorescent spectra are different with the wavelength of the excitation light.In the experiment the wavelength value of fluorescence peaks are found around two places:one peak is near 317 nm and the other is near 367 nm when the wavelengths of the light ranges from 220 to 270 nm.At this time the strife phenomena occur.After we compared the experiment results about the fluorescent spectra with some different excitation light,we find that the fluorescent intensities which are excited by 220,230,240,290,350,480,500 nm light are greater.The fluorescent intensities which are excited by other light are lower and the great peak values appear at around 317,365,367,388,348,463,467,607,638 nm.It is shown that the excitation light would give obvious biologic effect on the cow bloods.This study is valuable for selecting of the best excitation light wave in the technology of fluorescent spectra of cow bloods induced by excitation light.It provides basic information for the early distinguishing and diagnosis of cow diseases in the application of the fluorescence spectrum technology.关键词：cow blood;fluorescence spectrum106|69|0更新时间：2020-08-11
- 摘要：The concurrency frequencies and distribution areas of the water blooms in fresh water are increasing in China.It is not only destroying natural aquatic ecosystems,but also damaging human health.So,the study of this field is popular in recent years.To control effectively the water blooms,the important element is identifying the algae's species in the water blooms.By the coherent papers,we know the main species are blue algae,green algae and diatom etc.We develop a more effective way to identify the algae in the water blooms.Combined the microscopic imaging technology and spectrum imaging technology,we can use microscopic imaging technology for pattern classification firstly,and then use spectrum imaging technology for chemical separation of algae.Through the establishment of algae spectral cube by imaging spectrometer,which can be arbitrary pixel of the image spectrum.Two typical of the species selected for absorption spectroscopy-microcystis aeruginosa (blue algae) and chlorella pyrenoidosa (green algae).Different algae species have different pigments and different pigments have different absorption peak,so that distinguish easily between different species by absorption peak.But in the experiment,we abtained the absorption spectra superimposed of all the material in the algae.It is quite difficult to identify directly through the absorption spectra.So,we processed the spectra data using wavelet transform tools of Matlab 7.0.Wavelet transform can decompose signals into localized contributions of different frequency,it is a effective time-frequency analysis tool.Some decomposed components with some high frequency have the possibility to separate different absorption peak.By related papers and some experiences,we chose appropriate component to analysis the data.Experimental results show that the method was feasible.So,this paper provides a scientific and effective recognition way.It is of important guiding significance to prevent the water blooms.关键词：wavelet transform;algae;spectral imaging employing a microscope;absorption spectrum105|86|0更新时间：2020-08-11
- 摘要：Two series of Eu3+,Tb3+heteronuclear doped complexes with terephthalic acid(L) and 18-crown-6(L') have been synthesized.Elemental analysis,IR,UV absorption spectra,rare earth complexometry and fluorescence spectra have been studied respectively.The compositions of the complexes were confirmed to be Eu RELL'2(ClO4)4·nH2O and TbRELL'2(ClO4)4·nH2O(RE=Ce3+,Pr3+,Nd3+,Sm3+,Eu3+,Tb3+,Dy3+,Ho3+,Er3+,Yb3+;n=2,3,4).Terbium series complexes show that there is an excitation characteristic peak,which is a wide band from 230 to 340 nm,and a maximum peak is at 300 nm.To europium series complexes the band from 220 to 330 nm and maximum peak is at 261 nm.The excitation characteristic peaks are assigned to the ligands-metal energy transfer band through -COO-RE-OOC-.So 300 nm and 261 nm were chosen as excitation wavelength respectively to measure the fluorescence spectra of europium and terbium complexes.We all know that the UV absorption of 18-C-6 is weak,the5D0 energy of Eu3+is 17250,but 20430 cm-1for the 5D4 energy of Tb3+,and 25160 cm-1for the triplet energy of terephthalic acid.The triplet energy of terephthalic acid is higher a little than the excitation energy of Tb ion,but more higher than Eu3+ion's,the lowest excitation energy of Tb3+ion matchs well with the triplet state energy of the ligand each other.Thus it is possible that energy transfer from terephthalic acid ligand to Tb3+through -COO-RE-OOC- bonds more effectively.Absorbing energy of organic ligands are effectively transfered to the rare earth ion in the luminescence center,and producing a characteristic spectrum.Some non-fluorescence rare earth ions can absorb the energies of triplet organic ligand too,and then transfer them to Eu3+or Tb3+,in this way the fluorescence intensity was enhanced.If the transition energy of non-fluorescence rare earth ions is lower than the5D4energy of Tb3+or5D0energy of Eu3+,the luminescence will be quenched.Another way,the high-energy vibration of the OH of H2O molecules will heavily quench the luminescence of RE ions,so 18-crown-6 was introduced to replace some coordination H2O molecular.These results will provide relatively reliable criteria for the prediction of luminescence properties of rare earth complexes and for seeking excellent luminescent materials.关键词：europium complex;terbium complex;terephthalic acid;crown ether96|67|1更新时间：2020-08-11
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