最新刊期
卷 10 ， 期 1 ， 1989
- 摘要：Hydrogenated amorphous carbon films (a-C:H) were prepared by r.f. glow discharge deposition from C6H5CH3. The PL spectra and the Excitation energy dependence of the spectra were measured at room temperature using monochromatic light of 2.9-4.5eV for studying electronic structure. The PL spectra show featureless and very broad band (FWHM is about 0.8eV).From the plot that the peak energy EPL versus Ecitation energy Ex data,we identified two approximately linear regions, one with constant EPL at high Ex, and the other with a slope of 0.25. By assuming the Exponential density of localized states of band tails,considering two types of transitions of the carriers,the PL of a-C:H can be Eplained.One transition is that carriers make nonradiative transition from shallower to deeper states to lower energy or from deeper to shallower states because of thermal Excitation among the localized states of a band tail.Another transition is recombination among the localized states of different tails. The rates of two types of transitions are dependent on degree of localization of initial and final states. The deeplier state trapped, the less is the rate. Based on this model, the very broad band of the PL spectra is due to distribution of carriers on some energy region of broad band tail states.The red shift of the spectra with decreasing Ex, Excitation energy at sub-gap energy, can be obtained easily from distribution of carriers shifting to the deeper tail states. By the model we calculate the shape of the spectra and its changes with Ex.119|52|1更新时间：2020-08-11
- 摘要：Divalent europium ions shew strong absorption bands in the visible and near ultraviolet spectral ragions. Since Hoffman and Hewes[1,2] observed in some fluorides sharp lines corresponding to 4f-4f transitions of Eu2+ ions, great attention has been paid to the study of its spectral properties[3-8]. In contrast[14,15] to where only the broad 5d-4f emission band was observed in BaYF5:Eu2+, we report in this paper both the broad band and the narrow lines from Eu2+ in BaYF5. Moreover, their excitation and emission spectra have been investigated at 298K and 77K.Fig. 1a,1b and 1c show the emission spectra as a function of Eu2+ concentration under 260nm UV excitation at 298K and 77K. The emission spectra consist of a broad band corresponding to the 5d-4f transition and narrow line associated with the 6P7-8S7/2 (4f-4f) transition of the Eu2+ ion. The intensities of both the transitions depend on the Eu2+ concentration and temperature. There are two bread bands. 4f65d(eg) and 4f65d(t2g)in excitation spectra. The activators, Eu2+, are excited by UV from 4f7 ground state to 4f65d state then luminesce.The radiationless relaxation cf the higher 5d state (t2g) gives rise to the 6Pj-8S7/2 narrow line emission.96|63|2更新时间：2020-08-11
- 摘要：In general, a single crystal of ZnSxSe1-x contains native defects which arise from the deviation of stoichiometry in the growth process. These defects have an effect on the electrical and optical properties of single crystals.The purpose of the present investigation is to measure the change of the concentration of Zn vacancy(VZn)in the heat-treated ZnSxSe1-x wafers using the intensity of I1deep line in the exciton emission spectra.Because I1deep line is known to arise from acceptor of VZn[4]. For this purpose a wafer specimen was fabricated by cleaving along the (110) plane of the grown ZnSxSe1-x (x=0.03) single crystal. The wafers were heat-treated in the temperature range of 300-800℃ for 72 hrs.Under the composition (Zn or S/Se or Se) partial pressure and measured by photoluminescence at 4.2 K to observe the bound exciton emission spectra. The exciton emission spectra of the heat-treated ZnSxSe1-x in Zn pressure and in S/Se pressure at 300℃, 500℃, 800℃ have been shown in Fig,1-3 (a) and (b), respectively. The intensity of I1deep line becomes weaker with the increasing temperature of heat-treatment in Zn partial pressure. On the contrary, the intensity of I1deep line becomes stronger in S/Se partial pressure. This result means that the equilibrium between the vapor and the ZnSxSe1-x. solid during the heat-treatment is controlled by the Se partial pressure and the Zn partial pressure, respectively. Considering the following reaction.Se2(g)=SeSe+VZn (4)Zn(g)+VZn=ZnZn (5)where Sese and ZnZn are a Se atom and Zn atom occupying a normal Se and Zn site, respectively. Then the concentration of VZn increases with the increasing Se pressure, and decreases with the increasing Zn pressure.Dependence of the intensity ratio on the heat treatment temperature is shown in Fig. 4. It is known from the Fig. 4 that the concentration of VZn is not changed below 300℃,but a change of concentration of VZn is observed above 300℃. Considering that VZn and Cu-doping in ZnSe can separately be controlled[4]. Effective control of native defects and doped impurities in compound semiconductors was proposed in this report.111|39|0更新时间：2020-08-11
- 摘要：In recent years,interest in ZnSe has increased considerably as a potential candidate for blue light emitting diodes. Cu and Ga are important impurities in crystals of ZnSe.In this paper we study the effect of high Ga concentration on deep center emission in ZnSe:Ga,Cu crystals.Nominally undoped ZnSe boule crystals were grown by sublimation.ZnSe dice with dimension of 3×3×1mm3 were cut from the boules,and heated in molten alloy of zinc, gallium and copper with different concentration of Ga and Cu(Ga/Zn and Cu/Zn in weight respectively)to introduce the impurities and to obtain their low resistivities. Photoluminescence (PL)spectra in ZnSe crystals were measured using a Model 44W spectrometer with a C31034 pho-tomultiplier. A N2 pulsed laser of Model QJD-9 was used as the excitation source.Fig.1 shows the PL spectra of ZnSe:Ga,Cu with different Cu concentration when Ga concentration is equal to Cu.It is found that the Cu-G band is prominent in ZnSe crystal with high Cu concentration, while the Cu-R band is prominent in ZnSe crystals with low Cu concentration. This means that the intensity ratio of Cu-G band to Cu-R band increases with increasing Cu concentration,which was reported by Wang et al[12]. and Yamaguchi et al[1,2]. in ZnSe:Cu crystals.99|48|0更新时间：2020-08-11
- 摘要：Many authors have investigated the self-activated center(SA) in ZnSe crystals[1-4]. It is known that the chemical structure of the SA center ascribes to a FZn-D complex, here VZn is a Zn vacancy and D is a donor,and the acceptor related to the SA center is located at 0.65-0.75eV[5,6] or at 0.5~0.6eV[7] above the valance band. In this paper a deep acceptor level of Ev+0.65eV related to the SA center is determined for the first time by ODLTS technique[8-11]. Nominally undoped ZnSe crystals used in this study were grown by sublimation in our laboratory[12-13]. Dice of ZnSe were annealed in molten Zn-Ga alloy with different concentration of Ga at 900℃ for about 100h. ZnSe.Ga MS diodes were prepared by making In ohmic contact on one face of a die and evaporating Au potential barrier electrode on to the opposite face.125|62|0更新时间：2020-08-11
- 摘要：We have measured the integrated intensities of main emission lines for Tb3+, Er3+, Ho3+ ions in ZnS. TbF3, ErF3 and ZnS:TbF3, HoF3 ACEL thin films (TF) at low concentration, furthermore, compared them with their transition probabilities and their ACEL characteristics at high concentration.It is found that when the concentration is low(-10-4mol),the concentration quenching process could be neglected and transition probabilities of the main emission energy levels 5D4 2H11/2+4S3/2, 5S2(6F4)for Tb3+, Er3+, Ho3+ ions can be determined by decay time. The transition probabilities of 5D4-7F5, 2H11/2+4S3/2-4I15/2 and 5S2 (5F4)-5I8 are about 5300s-1, 13000s-1 and 7700s-1, respectively. In this case,the integrated intensities of main emission lines for Tb3+, Er3+ and Ho3+ in ZnS ACELTF are approximately proportional to the transition probabilities. But the maximum brightness of ACEL in ZnS:Tb3+, ZnS:Er3+ and ZnS:Ho3+ thin films is about 2300cd/m2, 1100cd/m2 and 500cd/m2 respectively. Therefore, the maximum brightness of ACEL in ZnS thin films doped with rare earth fluorides is not determined completely by the transition probability of rare earth ions themselves, but mainly depends on the concentration quenching process dominated by the cross-relaxation process of main emission energy level of rare earth ions.In the present paper, the intensity parameters for Tb3+ in ZnS thin film have been obtained for the first time. They are Ω2=3.2×10-19cm2, Ω4=1.6×1019cm2. Ω6=2.6×1019cm2. They have been used to estimate the cross-relaxation probability between Tb3+ ions. The calculated result is in agreement with the experimental observation.114|47|0更新时间：2020-08-11
- 摘要：In this paper, We reported two kinds of photoluminescence materials of red phosphor BaMg2Si2O7:Eu3+ and green phosphor BaMg2Si2O7:Tb3+ that we synthesized for the first time. With the aid of orthogonalizing method of the experiment design, the optimum proportion of host materials and synthesis temperature are determined. The mole ratio of SiO2/BaCO3/MgO is 2.14:1:1.96 at 1230℃. The emission and excitation spectra of the two kinds of luminophors are studied.We have investigated some factors that affect emission intensity of the materials. It is found either of Pb2+ and Ag+ have sensitive effect on Eu3+ in BaMg2Si2O7:Eu3+. Eu3+ emission intensity sensitized by Pb2+ and Ag+ is increased 230% and 80% respectively. With the doping of a little V2O5 into BaMg2Si2O7:Eu3+, the emission intensity ef Eu3+ is increased 160%. In either of these two materials, the emission intensity is increased 5-15% by the charge compensation of the alkaline metal ions (Li+,Na+,K+).It is found that the brightness of BaMg2Si2O7:Eu3+ is 45% that of YVO3:Eu3+ and the brightness cf BaMg2Si2O7:Tb3+ is 30% that of P1 (Zn2SiO4:Mn2+).It is necessary to make a detail research on this silicate materials because of their low cost, simple technique and the good application characteristics.103|35|1更新时间：2020-08-11
- 摘要：In this report the modulation frequency characteristics of InGaAsP/InP LED's were investigated. The InGaAsP/InP DH wafers used for fabricating the LEDs were grown by LPE technique. The structure of the wafer consists of four layers,they are a n-InP buffer layer, Sn or Te doped, a InGaAsP undoped active layer, a p-InP confining layer doped with In-Zn or Zn,a p-InGaAsP contact layer In-Zn or Zn doped.The carrier concentration profile of the InGaAsP/InP DH wafers was measured by electrochemical C-V method. The devices output power is about 1mW at 100mA.The modulation frequency was measured by a tracking scope. The experimental results are as follows.96|55|0更新时间：2020-08-11
- 摘要：This paper reports the study on the simulation of the shape of polarized spectra and on its application to analizing complex spectra. The 488nm-excited polarized fluorescence of chlorophyll a(Chla)solved in n-hexane is measured at 12.5K.New emission bands are observed.They are from the radiative transition of the higher excited state of Chla.The fluorescence spectrum of Chla is a superposition of several Gaussian components. Although a general theory that relates the polarized fluorescence intensities to the distribution of orientations, motion, local environments and energy transfer between the fluorescence molecules is very complicated, the spectra of Chla may still be very well explained by the results in Fig.l102|72|0更新时间：2020-08-11
- 摘要：The energy transfer in a proper mixture of dyes is now established as an effective mechanism of extending the wavelength region of lasing and of achieving more efficient conversion of pump light by an organic dye which alone has only small absorption at a particular pump laser wavelength (for example 337.1nm nitrogen line).It has been reported in literature that attempts made to lase safranin-T using nitrogen laser without a donor were unsuccessful,and accordingly Rho-damine6G/Safranin-T dys mixture is proposed to lase the latter.As is known that Coumarin 440 is a laser dye which strongly absorbs the 337.1nm radiation from the nitrogen laser.If an intermediary dye could be found to couple Coumarin 440 and Safranin-T spectrally,then an ternary energy transfer laser dye system might be formed. Motivated by this intention, we have investigated on the Coumarin 440/Fluorescein scdium/Safranin-T(C440/F1.Na/Saf.-T) dye mixture system. Since there are good overlaps between the fluorescence of C440 and the absorption of F1.Na and between the fluorescence of Fl.Na and the absorption of Saf.-T, and in the mean time the fluorescence quantum yields of these dyes are all reasonably high, we can predict an efficient energy transfer of the excitation from C440 cascading through Fl.Na to Saf.-T.102|74|0更新时间：2020-08-11
- 摘要：The optical coupling efficiency is an important parameter for the fiber communication devices, such as semiconductor laser, semiconductor laser amplifier and detector etc.This parameter shows how big optical power is coupled out through fiber from a semiconductor laser, how big optical power is coupled into a semiconductor laser amplifier or a detector.Until now there is no direct measuring method to get the optical coupling efficiency experimentally.In this paper a new method for measuring 77 has been reported. This method is based on the principle of short optical current of p-n junction.Suppose Pin(optical power)is incident on one of the cavity mirrors. If the incident photon energy is hv=Eg(the energy gap of semiconductor of active region),free carriers-electrons and holes-are excited. These free electrons and holes flow in opposite directions under the action of built-in field in p-n junction. The short optical current is composed of these free electrons and holes.Hence the short optical current can be used to measure the input optical power and to measure .The formulas of optical coupling efficiency for travelling wave laser amplifier are deduced.The short optical currents are measured by a galvanometer. Then the optical coupling efficiency are calculated by the formulas.Using the experimental data of, the dependence of gain of travelling-wave semiconductor laser amplifier on injection current is obtained. It is agree with theory.Besides,the measuring method of gain of travelling-wave semiconductor laser amplifier under pulse injection current condition is also given.117|75|0更新时间：2020-08-11
- 摘要：A Large electroluminescent (EL) matrix display for conference signal is applicated in the Great Hall of the Peaple.The result is satisfactory. It consists of ACEL and DCEL of phosphor material. The whole size of the AC-EL screen is 2.5×3m2 composed of 30 single green screen of 0.46×0.46m2. Average brightness is 20 cd/m2, and its contrast is 10:1. The size of DCEL screen is about lm2 with resolution of 120×144 yellow. Average brightness 45cd/m2, and contrast better than 10:1. Under room light condition, the display content could be seen clearly within distance of 65m,20m respectivelly. By analysing the characteristics of EL display for alphanumeric, it should be point that the control and match networks have important relation to brightness or contrast of EL display. Some block diagrams of the display and results of application are shown.99|68|0更新时间：2020-08-11
- 摘要：The semiconductor superlattice is a sort of new semiconductor materials developed lately.It has been used to make the laser devices, the field effect transistors and the optoelectronic devices. X-ray double-crystal diffraction is a powerful tool that can measure structure parameters of the super lattices, being nondestructive and having the advantage of high precision. In the paper, We applied X-ray double-crystal diffraction method to [(GaAs)l(Ga1-λAlxAs)m]n/GaAS(001) one-dimensional super lattices. On the ground of the step structure model and X-ray diffraction kinematics theory, we obtained a series of calculation methods for determining the superlattice parameters. Based on the appearance of the satellite peaks, existence of the superlattices can be confirmed. We can calculate the superlattices period D from the angular distance Ad between different satellite peaks. We can calculate the Al concentration x in the superlattice with relative intensity ratio of the satellite peaks. At last, we can obtain quantum well parameters, such as well width Lz,berrier region width LB and the molecular layer numbers 1 and m.Other informations obtained from the X-ray double-crystal diffraction rocking curves are also discussed.102|24|2更新时间：2020-08-11
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