最新刊期
卷 23 ， 期 2 ， 2002
- 摘要：We have studied exciton localization and delocalization effect in GaNAs/GaAs quantum wells (QWs) grown by molecular beam epitaxy (MBE) using photoluminescence (PL) and time-resolved PL measurements. Studied results suggest that, at low temperature and under a conventional CW excitation, measured PL spectra were dominated by localized exciton (LE) emission caused by potential fluctuations in GaNAs layer. However, under short pulse laser excitation, it is different. An extra high-energy PL peak comes out from GaNAs/GaAs QWs and dominates the PL spectra under high excitation and/or at high temperature. By investigation, we have attributed the new PL peak to the recombination of delocalized excitons in QWs. This recombination process competes with the localized exciton emission, which, we believe, constitutes the "Sshaped" temperature-dependent emission shift often reported in ternary nitrides of InGaN and AlGaN in the literature.关键词：GaNAs;IR;quantum well129|177|0更新时间：2020-08-11
- 摘要：The nitridation process of GaAs(001) surface was performed by exposing the surface of GaAs(001) to the flux of plasma-excited N2 gas directly and indirectly in MBE system.Two processes show completely different effect on the GaAs surface.The nitridation performed by opening N2 cell shutter resulted in deterioration of the GaAs(001) surface and formation of polycrystalline structure.With increasing of the N2 pressure during the nitridation,the deterioration became serious.However,for the surface nitrided with the closed N2 cell shutter,after nitridation process at 500℃,the(3×3) RHEED pattern was observed and the surface still kept atomically flat.Our results indicate that the nitridation (without opening N2 shutter) of GaAs(001) surface at low temperature (500℃) is suitable for the formation of thin c-GaN layer with flat surface before normal GaN epilayer growth.关键词：GaN;nitridation;MBE98|64|1更新时间：2020-08-11
- 摘要：The band gap tuning of multiple quantum wells (MQWs) structure in the compound semiconductor is becoming an important tool in fabricating optoelectronic devices.Especially,phonic integrated devices based on InGaAsP multiple quantum wells structure are particular imporance because of its dramatic increase in demand for long wavelength optical communication.To integrate several optoelectronic devices on a single wafer,we must divide area with different optolectronic properties such as refractive index and absorption wavelength.Selective regrowth and selective area epitaxy are two possible techniques that can be used for this purpose.However,there is considerable interesting in post growth quantum well intermixing (QWI) technique which can be used to modify the geometry and composition of MQWs in selected regions. There are several quantum well intermixing (QWI) techniques that provide the localized formation of band gap shifted area.Among these QWI techniques,impurity free vacancy disordering (IFVD)is believed to be a promising technique without free carrier absorption and damage of crystal lattice. In this paper, band gap blue shift of InGaAsP/InP multiple quantum wells by IFVD was investigated using photoluminescence(PL) and photoreflectance(PR).Si3N4 and SiO2 were used for the dielectric layer to create the vacancies.Then all samples were annealed by rapid thermal ananealing (RTA).The results indicate that band gap blue shift depends on the annealing temperature and time.Band gap blue shift increases with the annealing temperature and time but it tends to saturate when the annealing time attains certain extent.The SiO2 capping was successfully used with InGaAs cladding layer to cause larger band tuning effect in the InGaAsP/InP MQWs material than Si3N4 used with InGaAs cladding layer.On the other hand, samples with Si3N4-InP cap layer combinations also show larger energy shifts than SiO2-InP cap layer combinations.At the same time,the results of band gap blue shift measured by PR are basically consistent with the results from PL.So, photoreflectance(PR) is alternative method,which can be used to measure band gap blue shift.To our knowledge,no report was concerned with measuring band gap blue shift using PR.Furthermore,the band gap blue shift affected by cap layer combinations created a new method for IFVD investigation. Sum up,this paper first reports the results of band gap blue shift measured by PR.To obtain large energy shift,the optimal selected cap layer combination is Si3N4-InP or SiO2-InGaAs.关键词：impurity free vacancy disordering;photoluminescence;photoreflectance87|144|0更新时间：2020-08-11
- 摘要：The group-Ⅲ nitrides and their related ternary alloys have been becoming the most attractive material for light emitting diodes (LEDs) and laser diodes (LDs) in the UV and blue spectral range. However, the origins of the yellow luminescence (YL), which is commonly observed in almost undoped and n-type GaN, remain unclear. The nature and the role of initial nitridation of sapphire surface and the generation of threading dislocation (TD) are ambiguous too. It is a possible way to resolve the above problems by studying the microstructures and optical properties combining the growth conditions. In this work, two kinds of GaN films were grown by MOCVD under different initial nitridation time (180 seconds for Sample A, and 90s for Sample B). The growth temperature is about 950℃. The cross-sectional transmission electron microscope (TEM) is performed near the GaN/sapphire interface. Corresponding the growth processes, there are three zones in the GaN layer: buffer layer, "faulted" zone and "sound" zone. There are "haystack-like" domains in the faulted zone, in which there are high density of extended defects. The thickness of the faulted zone is about 0.4μm. Just above this region, the defects density is reduced sharply, and the quality of the layer is improved, which is identified by electron diffraction (ED) patterns. In comparison, Sample A shows about an order lower density of extended defects than Sample B, their columnar diameter is larger and its ED pattern is sharper, too. The buffer layer of Sample B is more smooth than Sample A. The appropriate rougher morphology of the buffer layer may cause that the structural disorder between the high-temperature (HT) grown island and the buffer layer is accommodated by Frank and Shockley partial dislocations. However, the TD is likely to propagate into the HT GaN from the smooth surface of the buffer layer grown after extensively nitridation of substrate. According to the position and width of X-ray diffraction peaks of (0002) and (0004), the size of crystalline grain, D and the residual strain could be calculated. The values of(D,εin)of Sample A and B are (175nm,0.167%) and (90nm,0.141%), respectively. Small size of crystalline grain may be advantageous to relieve the lattice and thermal mismatch stress, but it lead to higher density of extended defects. The width of GaN (0002) reflections of Sample A is 4min lower than that of Sample B. This result may be due to the lower screw TD. The higher density of screw TD may widen the GaN (0002) peak in X-ray rocking curve. In room temperature PL spectra, the ratio of band-edge emission intensity to YL one of Sample A is 3 orders larger than that of Sample B. Furthermore the YL in Sample B is stronger and has fine structure, while that in Sample A is nearly invisible in the PL spectrum. The GaN epilayer with high quality exhibits almost no YL emission. It is well known that the YL corresponds to the deformed crystal structure. We assigned that the screw TD and mixed TD are attributed to the YL referring to our XRD results.关键词：GaN;microstructure;optical property92|234|1更新时间：2020-08-11
- 摘要：In this paper, time-resolved photoluminescence(TRPL) was applied to study the optical properties of partially ordered quaternary (AlxGa1-x)0.51In0.49P(x=0.29) alloy grown by MOVPE, the process of the transfer of carriers and the blue-shift of PL peak in (AlxGa1-x)0.51In0.49P(x=0.29) alloy are directly observed.Both excitation-wavelength dependence of lifetime and excitation-intensity dependence of lifetime show wide distribution of carriers along bands.In TRPL spectra measured at 77K, the PL peak almost keeps unchanged, while at 300K, the PL peak has a small blue-shift with the delay of time, which is completely opposite to the character of donor-acceptor pair (DAP). The blue-shift phenomenon apparently suggests the occurrence of transfer of carriers and is coincident with the report of the Z-shape character of the PL temperature-dependent spectra, in which an anomalous blue-shift of PL peak energy occurs between 55K and 84K. This phenomenon further indicates the existence of sub-bands which is derived from the superlattice effect of ordered structure, which is a so-called orientational superlattice structure and which is considered to be a composite of the low-band-gap ordered domains in a high-band-gap disordered matrix. Thus, this phenomenon verifies our conjecture about band-folding effect of conduction band from L band to Γ band, i.e., the carriers transfer from Γ band to L band during the decay time. The transfer of carriers between Γ and L band reveals the origin of the anomalous blue-shift in the PL temperature-dependent spectra as well. The single exponential component fitting equation suggests the same category carriers of Γ band and L band. The transfer of carriers at 300K is more apparent than that at 77K. This is because that the blue-shift effect of PL peak energy occurs during 55～84K, the luminescence is dominated by L band at 300K and it is easier for the carriers to get energy to transfer under higher temperature.关键词：semiconductor;ordered structure;photoluminescence97|115|0更新时间：2020-08-11
- 摘要：The fundamental physical properties of Hg1-xCdxTe make it an excellent candidate material for infrared photoelectric detectors. Recently, much attention has been paid to Hg1-xCdx films grown by different epitaxial techniques on the substrate Cd1-yZnyTe due to the possibility of fabricating large area detectors as well as high precision focal plane array detectors. Investigations of the phonon vibration spectra for Hg1-xCdx are necessary to understand the lattice dynamics and to obtain structure information about the material. In this paper, the micro-Raman spectra of two MOCVD Hg1-xCdx/Cd1-yZnyTe epitaxial film samples were measured at room temperature within the spectral range of 50cm-1 to 5000cm-1. The quasi-periodically micro-photoluminescent structure in the range from 50cm-1 to 5000cm-1 was observed for the first time in one sample. The micro-photoluminescence results show that there is an anion vacancy resonance level far up in the conduction band, about 1.73eV above the conduction band edge in Hg1-xCdx/Cd1-yZnyTe epitaxial film. In the micro-Raman spectrum of another sample four main Raman peaks at 125.3cm-1, 140.8cm-1, 164.8cm-1 and 265.2cm-1 were observed. The Raman peak of 125.3cm-1 belongs to HgTe-like TO1 phonon vibrational mode, 140.8cm-1 belongs to HgTe-like LO1 phonon vibrational mode, 164.8cm-1 occurs due to CdTe-like LO1 phonon vibration, and 265.2cm-1 come from the two-phonon mode TO1(HgTe-like)+LO1(HgTe-like). At the same time, X-ray double-crystal rocking curves were also obtained in order to check the structure quality of two samples. Our results definitely show that the quasi-periodically micro-photoluminescent structure is mainly due to the improvement in quality of the Hg1-xCdxTe epilayer. The experimental results also demonstrate that micro-photoluminescence technique in micro-Raman system seems to be a good convenient, simple, contactless method to characterize the perfection of Hg1-xCdxTe epitaxial films.关键词：MOCVD;Hg1-xCdxTe epilayers;photoluminescence;Raman microscopy97|99|1更新时间：2020-08-11
- 摘要：Thin films of amorphous bulk Se0.70Ge0.15Sb0.15 system are deposited on a quartz and glass substrates at 300K by the thermal evaporation technique.The amorphous films were annealed at 370 and 470K in vacuum ～10-4Pa for 1h.The as-deposited and annealed films were checked by X-ray diffraction.On annealing at 470K(in the same time and vacuum),the films revealed crystalline nature.The optical constants such as refractive index(n),absorption coefficient(α)and extinction coefficient(k) were determined from the measured transmittance and reflectance at normal incidence of light in the wavelength range 300～2500nm.It was found that both(n) and (k) depend markedly on the temperature of heat treatment.The analysis of the optical data gave non-direct band gaps(Egnon)of 1.715±0.021,1.643±0.021 and 1.572±0.021eV for as-deposited,370K and 470K annealed samples respectively.The annealing temperatures are decreased the band gap(Egnon)and increasing the band-tail(Ee).This effect is interpreted in terms of the density of state model in amorphous solids proposed by Mott and Davis.The Wemple-DiD omenico single oscillator model parameterizes for as-deposited and annealed films are determined.关键词：amorphous;Se0.70Ge0.15Sb0.15 thin film;optical property;annealing91|69|0更新时间：2020-08-11
- 摘要：Cadmium selenide nanocrystals were synthesized with mercaptoacteic acid as stabilizer and different size of nanocrystals from 2nm to 3nm were obtained by size selective precipitation.The optical properties of CdSe nanoclusters were studied by optical absorption,photoluminescence (PL) and photoluminescence excitation(PLE) spectroscopies at room temperature.The UV-vis absorption spectroscopy shows sharp absorption spectra with clear excitonic features which indicating a narrow size distribution for our samples.Photoluminescence investigation shows that our samples have two luminescence bands,a sharp high energy hand with high intensity near the absorption edge attributed to radiative recombination of electron hole pairs after relaxation to lowest quantum dot level,and the other lower energy broad band is attributed to the trapping center at the matrix interface region.More than one band appeared in the photoluminescence excitation (PLE) spectra,assigned to S-S and P-P transition.The luminescence properties obtained for different excitation are also presented.关键词：CdSe;nanocrystals;photoluminescence;photoluminescence excitation93|143|2更新时间：2020-08-11
- 摘要：Recently, Yb3+ doped solid-state materials are attractively used as gain media of high efficiency, high power laser with the development of InGaAs laser diode. Yb3+ doped laser glass enable diode pumping without temperature stabilization because it has larger inhomogeneous width of the absorption lines. Due to broad emission lines around 1.02μm, Yb3+ doped glass also is a good candidate as a pump source for Pr 3+ doped laser fiber, which has potential application as amplifiers in the 1.3μm communication window. Determination of energy levels and other spectroscopic parameters of interest for Yb3+ laser action in glass is difficult because the inhomogeneous broadening of optical spectra is comparable to the Starke splitting, and hence masked the structure. However, a study of the energetic parameters of lasers and amplifiers require knowledge of the ratio between the homogeneous and inhomogeneous width of transitions. In this paper the absorption spectra of Yb3+ doped phosphate glass were measured at different temperatures and the blue-shift of the absorption peaks was discovered. There was abnormal absorption line in absorption spectra at low temperatures, which arised possible from another group of sites occupied by small partial Yb3+ ions. Due to the addition of B2O3,Al2O3 and Nb2O3, [BO4],[BO3],[AlO4]and [NbO6]partially take the place of PO4 tetrahedral as network formers. The [PO4]-Yb,[AlO4]-Yb,[BO3]-Yb and [NbO6]-Yb bond distances must be different and cause the great break of the symmetry of the coordination sphere of oxygens around Yb3+ ions. When a coordination sphere is surrounded by such network formers which possess different cationic field strengths, polarizabilities and coordination numbers of oxygen, the characteristic of Yb-O bond are varied and the local structures in the vicinity of the emitting ions may be distorted strongly, which result that a small portion of ytterbium ions reside in another type sites different from those occupied by the ytterbium ions which give rise to the principal spectra. The energy levels of Yb3+ ion in phosphate glass were obtained according to the absorption and emission spectra at low temperature. The sites selective fluorescence spectra had been investigated at low temperature, too.关键词：Yb3+-doped phosphate glass;selective excitation;absorption spectra;fluorescence spectra82|124|3更新时间：2020-08-11
- 摘要：The aim of our work is to produce enhanced Eu3+ luminescence in aqueous solution by using energy transfer between ligands, which are linked together by Y3+ without other additives and micelle formation. We synthesized two bifunctional complexing agents 2,2',6,6'-tetracarboxy-4,4'-bipyridine (BDPA) and bis(2,6-dicarboxy-4-pyridyl) sulfide (SDPA). In this polymeric network the enhancement of Eu3+ luminescence is based on two factors. First, a great excess of energy donors (ligands) relative to energy acceptors (Eu3+) was used. Excess of ligands was added to obtain maximum absorption and excess of Y3+ was added to link the ligands and enhance intersystem crossing to triplet state in these ligands. Secondly, the energy absorbed by ligands coordinated to Y3+ is transferred toward Eu3+ via triplet-triplet migration. One Eu3+ is able to be excited either with the energy absorbed by three ligands coordinated to Y3+, or by several other ligands coordinated directly. This means that when energy is lost non-radiatively during the energy transfer process from the ligand to the Eu3+, thus Eu3+ can still be excited by energy transfer process from other ligands coordinated to Y3+. The luminescence intensity of the Eu3+ was plotted against time after mixing of BDPA, Y3+ and Eu3+. The growth of the luminescence signal was quite rapid at the beginning, but slowed down 3min later. The SDPA system showed the same phenomenon. The ligand concentration, Y3+ concentration and pH were optimized. In two systems with different ligands the effect of pH was investigated in the range 3～11. The luminescence signal was observed to be highest at pH9. The effects of Y3+ concentration and BDPA concentration on Eu3+ luminescence were studied respectively. In the case of BDPA, the luminescence intensity of Eu3+ was highest when the Y3+:BDPA ratio was close to the theoretical value 2:3. When the luminescence intensity of Eu3+ was plotted against the concentration of Eu3+, it can be seen that there is a quite good linearity within 13+10-10～53+10-7mol/L range, which enables to be a method used for determination of trace amounts of Eu3+.It can be seen that adding of Y3+ will increase Eu3+ luminescence greatly. The enhanced Eu3+ luminescence is most likely due to the presence of efficient energy migration from the ligands coordinated to Y3+ to the Eu3+. The Eu3+(Y3+)-BDPA system reached the highest luminescence intensity. It might be the result of several factors. The BDPA has a symmetric, conjugated structure. This structure has the shortest distance between different Y3+ centers and its triplet energy level is suitable for transferring energy to the resonance level of Eu3+. It is totally conjugated and planar, which enables the effective energy transfer between ligands. However, the SDPA does not has a conjugated structure, and this may be responsible for the diminished energy transfer compared with that of the BDPA system. The effect of replacing Y3+ with other lanthanides such as Gd3+, La3+ and Lu3+ was also studied. The sequence of the enhancement is: Gd3+>Y3+>Lu3+>La3+. It is noticed that Tb3+ also enhances Eu3+ luminescence in this polymer structure.关键词：rare earth;luminescence;europium complex;yttrium complex98|110|0更新时间：2020-08-11
- 摘要：The intermolecular interaction and complex of various molecules can influence their optical and electrical properties,especially,efficiency of fluorescence and stability for fluorescent materials. Fluorescence decay experiment can demonstrate energy transfer among molecules and intermolecular interaction. In this paper,Fluorescence decay of the blending of polyvinyl carbazole (PVC) and tris(8-hydroxyquinolinolato) aluminum (Alq) with weight ratio 100:4 and 100:10 were investigated. The decay experiment is pumped by YAG locking-mode laser,whose excitation wavelength is 355nm,and detected by streak camera. Detection wavelength is chose 480nm and 540nm. According to the photoluminescence spectra of PVC and Alq film,these two wavelength correspond to the radiation emission of PVC and Alq respectively. Fiting the decay curve using a single exponential decay function,we get the fluorescent decay time. For the blending ratio 100:4,the decay time is 8.5ns at 460nm and 6.47ns at 540nm. For the blending ration 100:10,it is 7.9ns at 480nm and 5.5ns at 540nm. For Alq film and PVC one,their fluorescent decay time are 16.4ns and 14ns respectively. The blending of PVC and Alq show a evident reduction in fluorescent decay time compared with PVC and Alq. Thus in addition to the energy transfer between PVC and Alq molecules,there is a second channel to exchange energy, and the dynamics in this relaxation can be faster than that of radiation transition. This decay experiment implied that the interaction of PVC and Alq molecules formed a new complex of PVC and Alq,or configuration change of molecule.关键词：fluorescent decay;tris(8-hydroxyquinolinolato)aluminum;polyvinyl carbazole91|99|0更新时间：2020-08-11
- 摘要：White organic light emitting diodes with new blue material and two kinds of structures have been constructed:one with blue and red emission in a same layer,the other with blue and red emission in separated layers.The configurations of the devices are ITO/CuPc/NPB/JBEM(P):DCJT/Alq/MgAg(Device l) and ITO/CuPc/NPB/JBEM(P)/Alq:DCJT/Alq/MgAg(Device 2).Here copper phthalocyanine(CuPc)is the buffer layer;N,N’-bis-(1-naphthyl)-N,N’-diphenyl-1.1’-bipheny 1-4-4’-Ddiamine(NPB)is the hole transporting layer(HTL);9,10-bis(3’5’-diaryl)phenyl anthracene doped with perylene (JBEM(P))is a new blue emitting material;tris(8-quinolinolato)aluminium complex(Alq)is the electron transporting layer(ETL),and DCJT is a red dye.A stable and current independent white OLED has been obtained in the device with blue and red emission in the same layer.It shows a maximum luminance of 14.850cd/m2,an efficiency of 2.88 lm/W,Commission Internationale de I’Eclairage(CIE)coordinates x=0.32,y=0.38 (from 4mA/cm2 to 200mA/cm2), and the half lifetime 2 860 hours at the starting luminance of 100cd/m 2.It is proved that the device with blue and red in the same layer has better characteristics than the device with blue and red in separated layers in luminance,efficiency and stability.关键词：white OLED;current independence;stability98|125|2更新时间：2020-08-11
- 摘要：Heat treatment at the optimum condition on MEH-PPV OLED device with single-layer structure was performed. The surface morphology of the Al back electrode of the device after being operated at 12.0V is observed by Metallovert. It is found that the bubbles and black spots on the Al electrode surface was reduced and the luminescence performance of the device was improved obviously after the heat treatment. Compared with the unannealed device, the turn-on voltage of the annealed one is reduced by 2.0V, the maximum EL intensity is increased by ten times, the relative energy efficiency is improved by ten times at the same drive voltage, the half decay time is increased by 12.7 times. We analysised the reason of this result and considered that this is mainly because the bubbles and black spots caused by the evolved gases which were probably produced by the electrolysis of water coming from the humid air were reduced effectively by heat treatment, on the other hand, heat treatment also changes the characteristics of the interface between the light emitting polymer layer and the cathode by promoting the formation of the C-Al or C-O-Al chemical bond, this can enhance the interfacial adhesion and as a result, the electron injection is improved.关键词：OLED;MEH-PPV;heat treatment;black spots;interface98|80|1更新时间：2020-08-11
- 摘要：Since the discovery of poly(p-phenylenevinylene)electroluminescence in 1990,much effort has been devoted to the synthesis of various conjugated polymers and to adjustment of polymer energy gap by chemical and physical methods to realize the emission in whole range of visible light.Usually,among poly(p-phenylenevinylenen)and its derivatives,there are two kinds of methods to adjust their band gap.One is that the alkyl or alkoxyl sidechain are attached main chain to adjust the energy gap.Other is that the non-conjugated chain is inserted conjugated main chain,which can limit delocated-state electron in a short range and increase the energy gap.However,while the energy gap of conjugated polymer is adjusted by the alkoxyl chain or non-conjugated chain,we find that their attachment positions of main chain are related to the energy gaps. It this paper,we research the alkoxyl chain in the different position of main-chain how to change the luminescent properties.Here, the absorbance and luminescence characteristics of three conjugated-nonconjugated multiblock copolymers(CNCMBC)and three conjugated PPV derivative were investigated.For the alkoxyl radical in the side-chains of CNCMBC can strongly offer delocated electrons to conjugated main-chains,the band gap of CNCMBC can be significantly adjusted.Moreover,when alkoxyl chain locates in different position of various CNCMBC,the absorption and luminescent spectra shift.While the vicinity of carbon atoms in mainchain of CNCMBC can slightly affect the band structure.However,when the number rang of side-chain carbon atoms in conjugated PPV derivative changes from seven to twelve,the luminescence spectra are slightly changes and aren't significantly independent of band gap.Results show that the alkoxy chains in different position of PPV derivatives have different adjustment capability of energy gap.关键词：conjugated-nonconjugated multiblock copolymers;conjugated polymers;alkoxyl radical;structure of band gap93|135|0更新时间：2020-08-11
- 摘要：In the past decade optical recording media has become a subject of extensive scientific and industrial interest. Good stability, high optical sensitivity, high storage densities, and short access time for optical storage are very important. Azobenzene derivatives are typical materials displaying a reversible photoismerization and are of great potential application as optical information storage media and optical switching systems[1~4]. The incorporation of photoisomerizable azobenzene molecules in polymer matrix has been the trend of current research in the area of optical information storage materials because of the mutual exploitable characteristic performances, that is, the ease of device fabrication and the photoreponsiveness of azobenzene units, which can trigger property changes as a result of the conformational change of the molecules. In the previous work, novel azo dye grafted polyurethane (HSANB/PU) has been synthesized and characterized. In this study we report the laser-induced photoismerization property of this graft polymer. The UV-vis absorption spectrum of HSANB/PU film is shown in Fig.1, from which we can see that there are two absorption peaks at 320nm and 500nm, which attribute to cis-form and trans form of HSANB/PU respectively. Generally speaking, the absorption peak of trans form azo compound is at 440nm or so, however this peak shifts to nearly 500nm mainly because of the conjugating effect of benzene and naphthalene ring. Therefore Nd:YAG laser with the output wavelength at 532nm is used to induce the photoisomerization of the polymer film because it is in the resonance region. The spectrum of absorption versus time of HSANB/PU irradiated by 532nm laser with power density of 40mW/cm2 is shown in Fig.2, which shows that absorption at 520nm decreased, while absorption peak at 360nm increased when the sample is irradiated by the given laser, which indicated the trans-cis transition of the azo compound. Moreover the absorption at 520nm decreased steadily and the absorption increased steadily while the irradiation time ranges from 0～15min. The spectrum of absorption versus power density of HSANB/PU irradiated by 532nm laser for 60s is shown in Fig.3, which shows that the absorption at 520nm decreased steadily and the absorption increased steadily while the irradiation power density ranges from 2～40mW. The effect of intensifying irradiation power is equivalent to that of prolonging irradiation time. Moreover the photoisomerization threshold of the material is only 2mW/cm2.关键词：photoisomerization;azo dye;polyurethane;graft90|101|4更新时间：2020-08-11
- 摘要：Solid state analogy cathodoluminescence is a new kind of cathodoluminescence happening not in vacuum but in solid state materials like SiO2 with the properties of semiconductor.In our experiments,we selected the solid state material SiO2 as acceleration layer.The accelerated electrons with excite directly the luminescence materials in adjacent luminescent layer just like cathodoluminescence.The difference from cathodoluminescence lies in that the energetic electrons are accelerated not in vacuum but in solids.We prepared three devices of thin film electroluminescence with different structures.The phosphors layer is PPV and the accelerating layer is SiO2 in these structures.Solid state analyogy cathodoluminescence was found in these devices and the luminous dynamics of it was studies also.We prepared the existence of solid state analogy cathodoluminescence in our experiments.And the efficiency of devices with this kind of new structure has been improved compared with the of formal experiments without solid state analyogy cathodoluminescence.This new phenomenon of luminescence makes it possible to set up a new type of flat display technology.关键词：solid state analyogy cathodoluminescence;conduction current;flat display81|80|0更新时间：2020-08-11
- 摘要：The membranes of polydiacetylene backbone decorated with mannose can recognize Escherichia coli (E.coli) and bind with them. The binding leads to the color transition of the membranes which is readily visible to the naked eyes and can be quantified by visible absorption spectroscopy. The direct colorimetric detection by polydiacetylene membranes not only opens a new path for the use of these membranes in the area of biosensor development but also offers new possibilities for diagnostic applications and screening for binding ligand. In present paper, we utilized Langmuir-Blodgett technology to fabricate the mixed PDA/MPDA monolayers and measured the values of the colorimetric response when the mixed PDA/MPDA monolayers were incubated with various E.coli and physiological saline. On the basis of these measurements, we conclude the monolayers can be used to detect environmental E.coli. In order to understand the mechanism of the chromatic transition, the affinochromism properties of polydiacetylene are examined by Resonance Raman (RR) spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy. The results of RR spectroscopy demonstrate the bands of the double and triple bonds simultaneously shift to higher wavenumber during the affinochromism. At the same time, the bands intensity ratio of the double bonds to the triple bonds changes from a value 1.12 in the blue film to a value of about 2.5 in the red film, which can be explained by that the electronic structure in the polymer backbone changes from a acetylene to butatriene form when the blue to red chromatic transformation occurs. In addition, the results of FTIR spectroscopy also show that the side chains of polymer backbone perform rearrangement during the affinochromism. In conclusion, we demonstrate a simple and rapid method to detect E.coli and give a possible explanation to the mechanism of the affinochromism through RR and FTIR spectroscopy.关键词：molecular recognition;escherichia coli;Langmuir-Blodgett(LB) technology;mannose103|89|0更新时间：2020-08-11
- 摘要：As a nutrient supplement, Lei Zhen Zi Health-Care Capsule (Lei Zhen Zi) shows good effects on immune regulation and anti-aging. Its main components are procyanidolic oligomers, Ganoderma lucidum polysaccharides, gypenoside and vitamin C. Although some physiological effects of each component have been studied, the ability of Lei Zhen Zi as a combination form of nutrient supplement to scavenge directly free radicals, reactive oxygen species and reactive nitrogen species has never been investigated. In the present study, seven chemiluminescence systems and one colorimetric system, well established in our labora- tory, were used to elucidate the effects of Lei Zhen Zi on antioxidation and preventing DNA damage caused by ·OH oxidation. The experiments revealed that Lei Zhen Zi could effectively scavenge O2· produced in both xanthine-xanthineoxidase chemiluminescence system and pyrgallic acid auto-oxidation chemiluminescence system, but the 50% inhibition concentration (IC50) in the former (0.4μg/mL) was much lower than that in the later (50μg/mL). The reason for this phenomenon may be that in the xanthine-xanthineoxidase chemiluminescence system, Lei Zhen Zi can not only directly scavenge O2·, but also inhibit the activity of xanthineoxidase and reduce the production of O2·, whereas in the pyrgallic acid auto-oxidation chemiluminescence system, Lei Zhen Zi acts only as an O2· scavenger. The experiments also showed that Lei Zhen Zi could effectively scavenge ·OH produced in CuSO 4-Vit.C chemiluminescence system (IC 50=100μg/mL), H2O2 in H2O2-luminol-OH -system (IC50=0.5μg/mL), ONOO- in ONOO--luminol chemiluminescence system (IC50=50μg/mL) and the reactive oxygen species produced in whole blood phagocytes chemiluminescence system (IC50=12μg/mL). The DNA-protecting experiments showed that Lei Zhen Zi could effectively prevent DNA damage caused by ·OH oxidation through direct scavenge of ·OH. Above results indicate that the combination of nutrient supplement Lei Zhen Zi is an efficient antioxidant as well as a good DNA protector and the strong antioxidative activity of Lei Zhen Zi may be the important pharmacological base of its health-care effects. The present results can provide free radical biological data for the further investigation into the mechanisms by which Lei Zhen Zi functions as a health-care nutrient supplement.关键词：Lei Zhen Zi health-care capsule;reactive oxygen species;reactive nitrogen species;DNA damage;antioxidant86|87|3更新时间：2020-08-11
- 摘要：Color Plasma Display Panels (PDPs) has become one of the important developing trends in the information display field, phosphor is of critical role to the performance of PDPs. The phosphor in PDPs is coated by screen printing method. In the process of making into phosphor paste for screen printing and in the process of fabricating the PDPs, the performance of phosphor might be decreased. This is processing deterioration. After PDPs being finished the performance of phosphor could be decreased further with the continuous operation of PDPs. This is timing deterioration. The causes of occurring processing deterioration and timing deterioration are analyzed. The monocolor experimental PDP is manufactured. Chromaticity coordinates of phosphor in the PDP are measured by the CRT Color Analyzer (CA-100) which are compared with the chromaticity coordinates supplied by the phosphor manufacturer. Much data of processing deterioration and timing deterioration of phosphor is obtained. The experiment results show that (1) the processing deterioration of green phosphor (Zn2SiO4:Mn2+) and blue phosphor(BaMgAl10O17:Eu2+) is serious; (2) the timing deterioration of blue phosphor is most serious, y and x coordinate increasing by 10% and 5% respectively. We think (1) amending the phosphor paste ingredients and composition which results in the decrease of sintering temperature of phosphor, and using phosphor with larger specific surface area will be helpful to prevent the phosphors from processing deterioration; (2) amending the performance of MgO to enhance its anti-sputter ability, and using new driving method to prevent the phosphors from ion bombardment is helpful to improve the timing deterioration.关键词：PDP;phosphor;processing deterioration;timing deterioration79|109|12更新时间：2020-08-11
- 摘要：Color Plasma Display Panels (PDPs) is one of the important developing trends in the flat display field. The chromaticity coordinates measured on the PDP include two parts: the first part is chromaticity coordinate of phosphor on the PDP device, another is the chromaticity coordinate of gas discharge during the operation of PDP. In the process of fabricating a PDP, phosphor undergo the process of paste preparation, drying, sintering and aging etc. The chromaticity coordinates presented on the panel of PDP is thus somewhat different from that of raw phosphor. The aim of this paper is to measure the chromaticity coordinates of phosphor lighting. A new method is presented to obtain the chromaticity coordinates and brightness of phosphor on PDP by using the chromaticity coordinates and brightness of a monocolor and chromaticity coordinates and brightness of gas discharge under the same structure. A monocolor test panel is designed and fabricated for measuring the chromaticity coordinates of trichromatic phosphor lighting of PDP. The brightness and chromaticity coordinates of PDP and the brightness and chromaticity coordinates of gas discharge of PDP are all measured by using CRT Color Analyzer(CA-100). The chromaticity coordinates and brightness of phosphor on PDP is computed based on the linear superposition relation of tri-stimulus value of compound color and the tri-stimulus value of two known colors. At the same time, luminescence spectrum of PDP panel and gas discharge is measured with assembled multi-function raster spectrometer of WGD-3 type. The difference of two measured luminescence spectrum at the same wavelength is the luminescence spectrum of phosphor on PDP panel. The results show that the variation of chromaticity coordinates of green and blue phosphor is large and for red phosphor it is small which makes the white color temperature of PDP varies toward to the lower direction. The widths at half peak of luminescence spectrum of green and blue phosphor are both smaller than that of original phosphor. The peak luminous intensity is also decreased. The peak luminescence wavelength of green phosphor become 523.4nm from 526nm.关键词：PDP;phosphor;chromaticity coordinate;luminescence spectrum101|156|1更新时间：2020-08-11
- 摘要：An FAAS method for the determination of mass ratio of chemical composition in thin film transistors (TFT) of CdSe is proposed in this paper. Pure CdSe was used as common standard sample of Cd and Se in the separate experiment. Measured value of total weight and mass ratio of chemical composition for CdSe powder,and measured value of TFT film sample were tested separately in order to check the accuracy of this method. Their relative errors are 0.42%,-3.8% and -0.5%,respectively. The results show that this method can meet the need of accuracy. Because disturbing effects between two elements are eliminated in the determination process using a common standard sample,the accuracy of determination with this method is better than that using two different standard samples. Disturbance and recovery experiments are not necessary to do because both sample and standard are the same approximately in component and concentration. Quality and influence factors of CdSe TFT can be explained by measured value. If measured weight of CdSe matches formula weight,then the operation sequences are rational and the quality of thin film is better (shown by the results of Sample a#). As pressure of saturated vapor of Se is higher than that of Cd,Se is more volatilizable than Cd. Concentration of Se in CdSe powder left over evaporating dish is decreased with increasing times of film deposition. The samples of 3#、4# are typical examples. Analytic results have proved this conclusion.关键词：FAAS;cadmium-selenide;TFT;selenide;cadmium88|90|0更新时间：2020-08-11
- 摘要：Noise during signal transmitting of the display board is reduced by fiber communication system. Electric signal is first translated into optical signal in the output port of this system, and then it is modulated to electric signal in receive port again. The anterior control system all do exchange of electric signals mainly by computers and some large scale integrated circuits, so the frequency is limited by RC delay of wire and the exchange frequency of electronics. In order to make electronic exchange meet the requirement of communication power and little noise, the working velocity of electric chips should be improved greatly, this is too difficult. Now, for electric exchange system, the switch velocity is about 30～50ps, and the velocity of direct signal exchange is about 10～90Mb/s, which is approximately the limitation. For photoelectronic chip, the velocity of switch exchange is about 0.1ps, which has much higher frequency than electric chips. When optical or photoelectronic receive/restore chips are applied in stead of electric ones, the larger wavelength band can be obtained. In addition, optical exchange system can also reduce the working power and noise, and optical exchange system can be used in analog circuit transmit and digital circuit transmit. Fiber amplifier used in the display board, as a kind of optical exchange chip, is nonlinear fiber amplifier, which translates digital image signal and control signal of computer into optical signal. Signals are transmitted to the terminal (display board), and then they are translated into electric signal again. When the optical signal from fiber input port is amplified, the transmit will be nonlinear, which is not advantaged for transmit, but just because of this, it can be made fiber amplifier. The fiber used in display board is single mode one, which has less power loss, larger wavelength band. So the transmit distance is longer when using single mode fiber. Single mode fiber needs an excellent light source, which should be pure and steady, and has a narrow spectrum density and a much power. For display board, a indoor or outdoor product, safety is also very important, because there is static electricity in the terminal. So when someone checks this system, he might meet much trouble, even damage some parts. By fiber communication, these problems can be improved.关键词：display board;digital circuit;fiber amplifier83|78|0更新时间：2020-08-11
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