最新刊期
卷 8 ， 期 2 ， 1987
- 摘要：A calculation is given for the effect of confinement in GaAs-Ga1-xAlxAs quantum well on the binding energies of the exciton in which the interactions of the excition with the interface optical (SO) and the bulk Longitudinal optical (LO) phonon are taken into account, and the exciton is considered as the interacting electron and hole polaron.Assume the thickness of GaAs layer to be L, the origin of the coordinates in Z-axis at the middle point of GaAs layer,both GaAs-Ga1-xAlxAs layers are in contact with it at Z = ±L/2, and the depth of the well for the electron and hole are, respectively,Ve (Z) and Vh(Z), then the Hamiltonian of system consisting of the interacting electron and hole polar on and-phonon can be written as (1), where last two terms come from the interaction of the exciton with SO and LO phonoh.107|27|0更新时间：2020-08-11
- 摘要：The energy transfer and spectra behaviour of DMANS (4-Dimethylamino -4'-nitrostilbene)in solution and polystyene (PS) matrix have been studied by fluorescence spctroscopy and time corrected single photon counting technique. When the solvents polarity increased, DMANS fluorescence intensity and lifetime decreased and a red shift of fluorescence emission maximum was pb- served.For instance,in benzene with various concentration (from 1% to 28%) of cyclohexanol (the solvents polarity increased gradually) DMANS fluorescence emission maximum shifts from 578nm to 628nm and the fluorescence lifetime decreases from 2.5ns to 0.21ns. It can be interpreted that in polar medium electron transfer in DMANS molecule became more easily and the energy difference between excited state and ground state decreased. In PS matrix, when DMANS concentration increased, the PS fluorescence intensity and lifetime were decreased and the DMANS lifetime was decreased also. The dete are shown in the table.Table Lifetime of DMANS and PS in scintillators.When the lifetime was measured at 330nm,the PS emission was a single exponential decay owing to the energy transfer from PS to DMANS, the lifetime of PS was decreased as increasing DMANS concentration. When the lifetime was measured at 540nm, the DMANS fluorescence was a double exponential decay.The fast decay reflected the decay of direct excitation on DMANS and the slow one reflected the influence of the energy transfer from PS to DMANS.We used Stern-Volmer equation to calculate the PS quenching constant (Kq=3.0X×109M-1S-1) and and the decay rate constant of PS (K=1/τ0=4.3x×107M-1S-1).It means energy transfer from PS to DMANS efficiently, but the longer lifetime of PS will apparently influence the decay of the DMA-NS fluorescence scintillator. This study indicated that medium polarity effects scintillator's fluorescence quantum yield, absorbtion peak, emission peak and decay time.So it is important to select a suitable medium for getting a thigher efficiency, fast response scintillators.111|74|0更新时间：2020-08-11
- 摘要：The intra-and inter-molecular energy transfer and luminescence of europium chelates and triplet sensitizer-europium chelates in ethanol solution were investigated by fluorescence, phosphorescence and time-resolved emission spectro-scopies. The results are discussed.114|58|0更新时间：2020-08-11
- 摘要：Fluorescence decay of tetraphenylporphyrin (TPP) in toluene with added aromatic halides (RX)such as chloro-, bromo-,and iodo-benzene has been examined. It is found that the fluorescence of TPP is quenched by these additives and the quenching kinetical curve can be best fitted with a single exponential decay law with the decay time constant τ which is related to the nature of the halogen atom in the additives, but is independent of the viscosity of the medium. Furthermore, the relative intensity and the lifetime of the TPP fluorescence are decreased linearly with increasing the additive concentration in the low concentration range (Stern-Volmer relationship). But the concentration dependence deviates from this linearity with the further increase in concentration. All these observations appear to be understandable on the basis of a general analysis of bimolecular fluorescence quenching kinetics with an assumption of formation of a complex between the TPP chromophore and the additive molecule, provided that the rate constant of complex formation is much faster than those of processes leading to the fluorescence decay. Therefore, it is concluded that the observed fluorescence quenching of TPP in the presence of aromatic halides stems from the complexation between them rather than the enhancement of spin-orbital coupling behind the heavy atom effect as suggested in other cases. The linear dependence of kinetic parameters of fluorescence quenching by different halides on their electrochemical reduction potentials further implies that the complex formed is charge transfer in nature.98|100|0更新时间：2020-08-11
- 摘要：There has been considerable interest in recent years in blue electroluminescence (EL) emitted by forward-biased ZnSe MIS diodes[1-4]. Some of our earlier work[5-10] was concerned with the effect of crystal quality on its blue EL.128|62|0更新时间：2020-08-11
- 摘要：This paper reports the results on the synthesis of rare earth bqrate glasses and their luminscence properties.116|49|0更新时间：2020-08-11
- 摘要：Reaction mechanism of synthesis of europium-activated strontium fluorobo-rate phosphor has been investigated and the optimum reaction conditions for the formation of this phosphor have been evaluated and determined. Firing of a mixture of SrCO3, SrF2, H3BO3, NH4F and EuCl3 at temperature higher than 730℃, SrF0.1B4O6.95:Eu is the main product. As the firing temperature is lower than 730℃, a product of SrB6O10:Eu with weak emission might be formed. It was found to fire th3 product at 870-900℃ once more,so as to make the phase transformation of SrB6O10 to SrB4O7 comlpete. Firing atmosphere shows certain influence on the luminescence intensity of the product.Firing in the presence of granular active charcoal (i.e.in an atmosphere of CO+CO2) would be the most favorable. The optimum activator concentration was determined to be 0.01mole/mole host. As it is higher than 0.015mole/mole host, concentration quenching would occur.By the X-ray diffraction, thermogravimetric as well as chemical analysis of Sr2+ and Fions the chemical composition of the phosphor was determined and its general formula can be written as(l-x)SrO·xSrF2·2B2O3:yEu 0.02≤x≤0.05 0.005≤y≤0.015.98|70|0更新时间：2020-08-11
- 摘要：A broad band peaked at 1.71eV is commonly observed in the PL spectra of n-GaP[2-4,10]. Comparing the PL spectra of epitaxial layer with that of the substrate, both have similar behaviours within the interested region. It can be concluded that the band stems from some background impurities or defects in the substrate. The shape of the broad band (Fig. 1) indicates that the band is a superposition of several bands.104|56|0更新时间：2020-08-11
- 摘要：The p-GaAs, p-InP are the cap layer material of the photoelectronic devices. The influence of the characteristics of p-electrode on the parameter of the LED with Cr/Au or Au-Zn alloy p-electrode contact material have been studied. The investigation of the interface between the p-GaAs, p-InP and contact metal, and electrical characteristics is important for improving parameters of the devices and their reliability. In this work,the Zn diffused GaAs and Zn doped single-crystal InP polished wafers were used as the starting material. The small pieces of the sample were placed into evaporator equipment. The samples were processed by the vacuum-evaporating Cr 500Å, Au 3000Å, then the samples heat-treated at 450℃ for 5 min in pure nitrogen atmosphere.The surface morphology of the samples after heat treatment was observed by SEM. The effect of alloy temperature on the specific contact resistance (ρc) was studied. The interdiffusion of p-GaAs/Cr/Au and p-InP/Cr/Au at interface has also been investigated by AES.It was found that the interdiffusion of Au does not occur during the heat treatment of p-GaAs/Cr/Au system. The Cr layer as a diffusion barrier plays an important role, ρc=6-8×10-5Ω·cm2. The Cr/Au layers are used as pelectrode for GaAs/GaAlAs DH LED. The I-V characteristics of the devices do not change after 5×103 hours CW operation at If=100mA condition. The results indicated that the p-GaAs/Cr/Au system has good stability.Interdiffusion of Au, In and P occurs during the evaporation, therefore, p-InP/Cr/Au system is not a good p-electrode material for the p-InP/InGaAsP devices.105|75|0更新时间：2020-08-11
- 摘要：Deep levels in the n-Al0.05Ga0.95As active layer of AlxGa1-xAs/GaAs double-heterostructure light-emitting diode have been studied by using DLTS and single shot transient capacitance methods. Two electron traps and one hole trap were detected for all six oxygen-contaminated samples. DLTS peaks were studied at 145K, 171K and 125K respectively. However, no electron trap can be detected for three samples that have not been contaminated with oxygen. Therefore, we consider that the electron traps are probably related to impurity oxygen. Meanwhile, the electron trap whose DLTS peak is located at 145K was characterized in detail. Firstly, the electron emission activation energy △Eσ of 0.29eV of this trap was determined from an Arrhenius diagr.am. The DLTS peak shifts to lower temperatures while bias pulse duration increases. This shift may be caused by the change of electron capture cross section because the change of electron emission activation energy was not observed. Secondly, the electron capture activation energy △Eσ of 0.26eV was determined by measuring the dependence of amplitude of DLTS peaks on bias pulse duration. The electron capture cross section corresponding to infinite temperature o. was determined to be 1.9×10-12cm2. Single shot transient capacitance technique of directly measuring the capture transient spectroscopy was also used for the first time and the electron capture activation energy △Eσ obtainded is 0.26eV to 0.28eV in accord with the result of the method mentioned before. △Eσ varing from 0.26eV to 0.28eV is due to the change of evaculating pulse duration Such phenomenon can be interpreted as a result of composition fluctuation or mutiple origins of this electron trap. Finally, it was found that the junction capacitance of the diode shows manifest temperature depeneence. This is caused by the temperature dependence of carrier concentrations in Gedoped p-AlxGa1-xAs and Te-doped n-AlxGa1-xAs confinement layers.100|66|0更新时间：2020-08-11
- 摘要：Sr2B5O9Cl is a polycrystalline powder luminous material, in which some people have taken much interest. Hao Zhiran and his coworkers prepared Sr2B5O9Cl(F) structure by charging F/C1 ratio and substituting Cl ions by some F ions. Thus the luminous property of the raw material was changed greatly. In order to interpret the structural change due to the mutual substitution of F?C1, it is necessary to determine the unit cell parameter precisely.95|33|0更新时间：2020-08-11
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