最新刊期
卷 4 ， 期 4 ， 1983
- 摘要：Photoluminescence of single crystals and sintered slices of ZnS:Sm3+ was investigated. Sm3+ ions were introduced into samples by thermal diffusion. Three groups of lines,at 570nm,600nm and 650nm,were analyzed. They correspond to transitions of 4F5/2-6F5/2,4F5/2-6F7/2 and4F5/2-2H9/2,respectively.In the emission spectra of 4F5/2-6H5/2 transition of Sm3+ in ZnS(Fig.l) it was found that there were two groups of lines:lines 1,2 and 6 belonging to group It and lines 4 and 8 belonging to group I. The lines of group I keep the same relative intensities in different samples and the lines of group I also do so.From time resolved spectra it was found that the lines of the same groups had the same decay time.The lines of group I have decay time of 643us and group I has decay time of 475us (Fig.2). These two groups of lines also have different excitation spectra(Fig.3).The above experements prove that two groups of lines come from two different Luminescent centers,group I comes from center I and group II from center Ⅱ.102|47|0更新时间：2020-08-11
- 摘要：We have systematically studied the interaction between Mn2+ and Sm3+ centers in ZnS. The time resolved luminescence spectra of ZnS:Mn2+ ZnS:Sm3+ and znS:Mn2+,Sm3+ have been measured.It is found that energy transfer takes place between Mn2+ ions and Sm3+ ions.The time resolved luminescence spectra show distinctly the process of the energy transfer from Mn2+ to Sm3+. In case the znS:Mn2+,Sm3+ is excited by the light pulse of a dye laser line of 530nm,as shown in Fig.9,the emission of Sm3+ can be observed only after a delay time larger than 10us. Then,the emission of Sm3+ increases with the increase of the delay time,followed by a decrease of the Mn2+ emission band. The Sm3+ emission reaches its maximum value at about 370us.On the other hand,if ZnS:Mn2+,Sm3+ is excited by the light pulse of a N2 laser line of 337nm with which both Mn2+ and Sm3+could be excited,as shown in Fig.6,after excitation the emission of Sm3+ appears immediately as that of Mn2+,but the intensity of Sm3+ emission increases with time until it reaches its maximum value at about 12ns.133|35|0更新时间：2020-08-11
- 摘要：ZnS doped with rare earth ions is an important luminescence material. But very few works have been done in finding their Judd-Ofelt parameters so far. The reasons are:(1) The solubility of rare earth in ZnS is so low that it is difficult to measure the absorption spectrum. The standard method to get s from the measured absorption spectrum is unavailable.(2) It is well known that rare earth ions form a variety of luminescence centers in ZnS. These centers may have different s and their spectra may sometimes overlap.Along with the progress in experimental technique and the gain of the knowledge about luminescence centers in ZnS:RE,these difficulties could be overcome at least for some rare earth ions.94|66|0更新时间：2020-08-11
- 摘要：The earlier experimental results showed that the luminescent characteristics of Tb3+ ion depend on Tb3+ ion concentration and crystal hosts.In this paper theoretical investigation of Tb3+ luminescent characteritics in pentaphosphate and mixing pentaphosphate single crystals (TbP5O14 and TbxY1-xP5O14) has been carried out. By using the Judd-Ofelt theory and absorption spectra,the parameters of the oscillator strengh were first obtained in TbP5O15crystals,resulting in O2=2.13×10-20cm2,O4=3.76×10-20 cm2,O6=2.98×10-20cm2.The probabilities of electric dipole and magnetic dipole radiative transition from 5D3 and 5D4 to 7FJ were calculated. The lifetime of electron in5D4 obtained is 4.4ms,which agrees with experimental value.89|39|0更新时间：2020-08-11
- 摘要：The temperature dependence of photoluminescence intensity for a number of samples of a-Si:H,a-Si:H,F,a-Si:H,C1 and a-Si:H,Cl,O has been studied. The activation energies for nonradiative recombination were measured as a function of preparation conditions. We deduced the band tail distribution parameter T0 from the temperature dependence of photoluminescence,and the correlation between T0 and the line shape of PL spectra has also been investigated. The results were compared with that obtained from the transient photoconductivity measurementFig.1 shows the typical photoluminescence spectra of samples a-Si:H,a-Si:H,C1 and a-Si:H,F at LN temperature.These samples all exhibit single,broad featureless photoluminescence peaks near 1.3eV when excited with 2.4eV light. The differences in peak position and line width are due to the differences of sample preparation conditions and dopants.In Fig.2 the logarithm of is plotted as a faction of inversetemperature based on Eq.(3).An approximate linear correlation suggests that a single activation energy can be deduced from each curve in the temperature region 77-200K. The difference in numerical value of activation energies of different samples reflects some intrinsic properties(e.g. the gap states)of the samples. This would make it possible to use the activation energy as a measure of the gap states. We plot in Fig.3 the activation energy and the saturation PL intensity at LN temperature versus the relative oxygen content in a number of samples.It can be seen from this figure that as the oxygen content increases,above some value,both the activation energy and the saturation PL intensity decrease monotonically. This suggests that the activation energy could be taken as a measure of gap states as in the case of saturation PL intensity.We deduce the band tail width E0(E0=KT0) also from the measurement of the temperature dependence of photoluminescence intensity based on Eq.(1) and Eq. (5).The correlation between the spectrum width and the band tail width for a large number of samples is plotted in Fig. 4. The trend in this figure implies that the FWHM may be used as a relative indicator of the band tail state-density distribution.For the comparison of T0 from PL measurement with that from PC measurement see Table 1.133|61|0更新时间：2020-08-11
- 摘要：CaSb2O6:Mn is an impurity phase in calciumhalophosphate phosphors,which it can influence luminescent properties of phosphors and also shorten the lifetime of phosphors. So far there is only a few work on spectra of Ca-Sb2O6:Mn. In this paper emission spectra of CaSb2O6:Mn were measured and investigated in detail.Excitation spectra were measured from 240nm to 340nm. When samples were excited by different wavelengths of ultraviolet light (220,230,240,250,254,260,270,280,290,300,312.6,320),a series of emissiol.spectra were obtained.Preparation of CaSb2O6:Mn.1)CaSb2O3:Mn seperated from commercial calciumhalophosphate phosphors. Dissolve the commercial calciumhalophosphate phosphors by HC1 acid. The insoluble material is CaSb2O6:Mn which emits a green fluorescence under excitation of UV light.2)Synthesis of CaSb2O6:Mn.Synthesized CaSb2O6:Mn was prepared by solids state reaction:raw materials calciumcarbonate,antimony trioxide and manganese carbonate were mixed and then fired at 1100-1200℃ in air for one or two hours.The concentration of Mn is nominally about 1%.In the emission spectra of synthesized CaSb2O6:Mn or of that seperated from calciumhalophosphate phosphors,a broad emission band near 395nm is observed(Fig.1 and 2).It is found that the intensity of this broad band increases with the increasing of exciting wavelength when the latter is shorter than 254nm,but when the latter is longer than 254nm,the emission intensity decreases (Table 1 and 2).95|48|0更新时间：2020-08-11
- 摘要：The relationship of the brightness B and the anode voltage Va for the low energy electron luminescence(LEEL) may be expressed byβ= QVanwhere Q and n are constants. This equation shows that the brightness is proprotional to Van. But at higher anode voltages,the brightness gees through a maximum and then decreases. That is so-called "brightness saturation" of LEEL. In this paper,the basic physical reasons of the brightness saturation have been discussed. It was pointed out that when Va=Vg(Vg is the grid voltage) the brightness saturation is not due to thermal quenching or dynamic saturation of the luminescent centres,but mainly due to the following processes:first,the electron emitting from the cathode is fatigued,resulting in a decrease of anode current density,and second,the ratio cf the anode and the grid current densities is decreased,since the secondary electron emission of ZnO:Zn increases with increasing applied anode voltage. For a flat triode luminescent device the ratio Ia/Ig may be given bywhere u is a constant,o(Va)is the effective cross section of the grid,d. and dg are the distances from the anode and from the grid,to the cathode respectively. When a voltage much less than that of the anode is applied to the grid,the secondary electrons emitted from the znO:zn will return to the anode,so the above expression can be simplified as As can be seen,the ratio of the anode and grid current densities increases with increasing (Va)1/2. In this case,the saturation brightness will obviously increase,e.g.,4230cd/m2 for Va=Vg and 8918cd/m2 for Vg<<Va. It has been found that there is an optimal value of the anode current density,corresponding to the optimal luminescent efficiency. For a given input power,the luminescent efficiency at low anode current density and high anode voltage is always rather poor. As is well known,because the power efficiency of LEEL is only a few percent,most of the kinetic energy of the electrons is converted into heat. When the input power is high,the temperature of the luminescent layer will obviously increase. Therefore,when Vg>>Va,the principal factor for the brightness saturation will be thermal quenching. The brightness is related to the input power W0 bywhere a and b are constants,B10 is the brightness at 10℃,P the power efficiency,the thermal conductivity,d the thickness of the anode substrate,and TO the temperature of the external surface of the substrate. For a given anode currect density,the optimal input power Wm corresponding to the efficiency maximum can be written asFinally,according to the results mentioned above,a luminescent device with saturation brightness of 37,000cd/m2 as well as a high brightness vacuum fluorescent numerical display tube havebeen manufactured. The brightness of the display tube increases with increasing anode voltage and reaches a maximum(22,000cd/m2) at about 157V. At still higher voltages,the temperature exceeds the quenching temperature of the ZnO:Zn phosphor and the brightness decreases. The display tube can be steadily operated at the brightness of 5,000-10,000cd/m2 (at Va=40-65V),and a good legibility in a high ambient illumination (e.g.,bright sunlight falling directly or an ambient illumination of 100,000lux) can be achieved.104|53|0更新时间：2020-08-11
- 摘要：Recently much attention has been paid to the study in blue LEDs of ZnS. In order to make efficient LEDs of ZnS,a basic problem,i.e.the reproducible preparation of low-resistivity bulk materials must be solved.In this paper,we present a method to produce low-resistivity ZnS:I crystals end discuss the influence of iodine concentration in ZnS:I crystals on annealing condition.ZnS single crystals studied in this work were grown by I-chemical vapor transport.The crystals were cut into slices 1.5mm thick.After chemical cleaning and etching,they were heated in a molten mixture of Zr-Al (1.5-2%) in a sealed quartz ampoule which was coated by careen film for 40-100 hours at 950℃ and then were quenched immediately in cold water.Both faces of samples were lightly polished and toiled in a solution of 25% NaOH-in-H2O for 30-60sec and then washed in hot deionized water.The chmic contacts were made by heating In-Ga alloy in N2 flow at 400℃ for 5-10 min. The resistivity of samples were mesured by Van der Pauw method of from I-V characteristics.ZnS:I crystals usually shew different bulk colour. According to difference of the bulk colour,ZnS:I crystals can be divided into three kincis:A--Colourless and transparent;B--Yellowish and C--Yellow.Chemical analysis shows that their I concentration is 45,100 and 130 ppm respectively.It is identified that the bulk colour of crystals is correlated with iodine concentration in the crystals. The higher the iodine concentration,the darker the bulk colour.It is found that different annealing conditions are needed for ZnS:I crystals with different bulk colour in order to obtain the same resistivity.Having taken suitable annealing condition,Al concentration in ZrS:I crystals can be controled at the order of 10-3g/g and the resistivity of ZnS:I slices can be reduced down to 10-102.cm.The MS(metal-semiconductor) junction made by the low-resistivity ZnS crystals can produce blue EL. The emission peak is located at about 4500A at room temperature. Finally,the influence of iodine on Al diffusion was discussed by means of volume compensation principle.In general,iodine ions enter into ZnS crystals at the substitution site and yet the ion radius of iodine is bigger than sulphur ion. On the other hand,aluminum ion is smaller than zinc ion. So Al ions occupy more easily those vacancies which are the nearest neighbors of the iodine ions during annealing.That is,doping of iodine ion may influence on Al ion diffusion to a certain degree. Therefore under the same annealing conditions,for a higher iodine concentration in ZnS crystals,a large amount of Al can be incorporated in the lattice.It is concluded that the diffusion of Al impurity have not only a connection with annealing condition and Zn-Al alloy composition but also with the iodine concentration in ZnS crystals. Different annealing conditions are needed for ZnS:I crystals with different iodine concentration(i.e. different bulk collour) o obtain same low resistivities.89|55|0更新时间：2020-08-11
- 摘要：The cylindrical surfaces of ZnS and ZnS:Cu single crystals grown from the vapour phase frequently show some parallel striations perpendicular to the c-axis. They are sparse in the smooth zone of crystal surface and dense in the step-like rough surface zone. We call these striations "the growth-layer lines" (GLL) in the present paper. When the ZnS:Cu crystal is put in an a.c. electric field electroluminescent lines (ELL) lying on the GLL and situated frequently on the <1120>irection are observed with the shape of comet and appearing in pairs. The degree of the dense of the ELL and GLL along c-axis are corresponding to each other. But these lines are not in one to one corresponding,i.e.,there may be no ELL in some regions where there is GLL.The crystals were grown from vapour phase at 1050℃. The structure of three crystal regions has been analysed by means of the X-ray rotation potograph. The results indicate that the structure of the zone without GLL is ordered 2H-ZnS; in the zone where GLL’s are sparse the structure is 2H seperated by a lot of stacking faults with random distributions in the zone with dense GLL,most part has the 2H structure while the rest is of the form of 3C-ZnS and 4H-ZnS (or other polytypes),all of them being also separated by stacking faults with random distribution. It should be pointed out that in the c-axis rotation photogaph for the zone with dense GLL,an unsymmetrical arrangement,with respect to the zero-layer line,of the spots of 3C and 4H on the h-k=3r (r=0,±1,±2,...) row has been observed. Such kind of asymmetry results from a small displacement of the corresponding reciprocal lattice point along e* direction. The small displacement may be due to a displacement of the atom on the close-packed plane.It is shown that the structure of GLL zone is formed during crystal growth and during the cooling down period. The structure transformation of 2H--3C-ZnS occurs through a disordering process of 2H.The random distribution of the stacking faults (disorder) always appears in the zone of GLL. The experimental results in the present paper and in a later investigation (to be published) show that the random distribution of the stacking faults is a necessary condition for the appearance of EL in the ZnS:Cu crystal grown from vapour phase.108|96|0更新时间：2020-08-11
- 摘要：MO-CVD is a chemical vapor deposition method using organometallic compounds as starting materials. It has showed the unique advantages for the preparation of materials at high purity and thin layer and has been extensively used. There fore,much attention has been paid to the MO-CVD method recently.In this paper,the principle,features and applications of organometallic compounds chemical vapor deposition(MO-CVD)have been reviewed and the preparation of II-VI compounds by MO-CVD method has been specially disscused.94|120|0更新时间：2020-08-11
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