最新刊期
卷 8 ， 期 4 ， 1987
- 摘要：This review gives the progress of Ⅱ-Ⅵ compond powder luminescent materials in recent years.First of all,akaline sulfide material doped by rare earth ion are being paid renewally attention,some progress of which in catho-doluminescent,and direct current electroluminescent material are reported.Then,some efforts are made to overcome the maintenance problem in ACEL,results show that the possibility of improved AC powder devices is now very real.Finally,typical copper rich phase in EL are noticed not only in some suggestion models but also in designing experiments for examine its function.113|44|0更新时间：2020-08-11
- 摘要：A theory of charged particle-phonon interaction in dielectric bilayer systems has been developed by Wendler and Pan Jinsheng.In these papers the interaction between charged particles and phonons in a quantum well is taken into consideration.A calculation is given for the binding energy of the ground state of the charged particles in GaAs-Ga1-xAlxAs quantum well by use of perturbation method.The variation of the binding energy of the charged particle with the well width are discussed.It is shown that the interaction between the charged particles and phonons must be taken into account in quantum well.116|41|0更新时间：2020-08-11
- 摘要：GaN has a direct bandgap of 3.5eV and thus gives luminescence over the entire visible spectrum.Zn dopants are disposed for a broad blue luminscence bands in GaN,but the nature of deep centres responsible for their bands is not well established,nor is the radiative mechanism involved.A detailed study of 2.89eV photoluminescence(2K)transient in GaN:Zn at different time range was given.The lifetime turns out to be 300ns at 2K(Fig.3)and slightly faster at 77K,in accordance with the result obtained from time-resolved spectroscopy(Fig.4).However,the decay-curve of long-period(50 μs)is nonexponential,fitting the Becqueral type of relation.Its kinetics appears to be more complicated.The luminescence intensity decay obeys the law of I=Ic/(1+bt)a.We have found a=1.8 from the analysis of experiment curve(Fig.5).This demonstrates that the luminescence should be interpreted as a bimolecular mechanism rather than monomolecular.Its decay corresponds to a hyperbolic curve approximately.Temperature dependence of 2.89eV luminescence has been observed.The rapid decrease of 2.89eV luminescence efficiency can be seen above 160K.It is responsible for nonradiative transitions full sense.The assumption is consistent with those obtained by other authors.These values of activation energy for the nonradiative recombination have a range of 0.18-0.49eV.In conclusion,it is clear that the transient process of deep centre Zn in GaN is not so simple,Zn not only forms a deep acceptor,but causes non-radiative recombination or other traps probably.Our results show that Zn is complex centre.The nature of 2.89eV blue luminescence is interpreted as due to the radiative recombination between photo-excited electrons in conduction band and holes bound at the ZnGa acceptor taking into account traps perturbation.111|44|0更新时间：2020-08-11
- 摘要：Recently there has been considerable interest in blue electroluminescence in ZnSe diodes.The most important problem in obtaining good blue electroluminescence diodes is to prepare ZuSe single crystal with high purity and perfection.In ZnSe,copper is an electrical and Optical active impurity and forms deep levels to produce deep center emissions and suppress near-band edge emission.Therefore,it is necessary to study the behavior of copper impurity in ZnSe.Many authors have investigated the Cu-G and Cu-R deep centers in Cu-diffused ZnSe crystals.In this paper,two Cu-doped ZnSe crystals are prepared by the diffusing techniques at low or high temperature,and two deep acceptor levels,Ev+0.30eV and v+0.72eV,related to Cu-G and Cu-R centers are determined for the first time by ODLTS technique,respectively.Nominally undoped ZnSe crystals used in this study were grown from the Vapour phase in sealed capsules containing slight excesses of zinc in our laboratory.Two different methods are used to obtain the superior Cu-G and Cu-R centers respectively.First the Cu impurity was diffused into the ZnSe crystal at high temperature.Dice of undoped ZnSe were annealed in molten Zn-Cu-Al alloy at 850℃ for 100h to reduce their resistivities and Cu-R center was formed at the same time.Second,the Cu impurity was diffused into the ZnSe crystal at low temperature.Copper was deposited on the surface of low resistive and undoped ZnSe dice by vacuum evaporation technique,then the dice are heated in N2 atmosphere at 400℃ for 20min.Diodes are prepared by making In ohmic contact on one face of a dice and evaporating Au potential barrier electrode on to the opposite face.Fig.1 shows the ODLTS spectrum in ZnSe:Cu,Al crystal diffused at high temperature.Only one peak corresponds to a deep acceptor level with activation energy of Ev+0.72eV is appeared.A red emission band,which peaked at 6350Åat RT and at 6320Åat LNT,is obtained in electroluminescence spectra as shown in Fig.2,respectively.The peak position of the red emission band corresponds to that of Cu-R emission band.Fig.3 shows the time resolved spectra of red emission band in ZnSe:Cu,Al crystal at 77K.This spectrum gradually shifts to the low energy direction as a whole with decay time.It indicates that the recombination process of the red band ascribes to D-A pair transition.According to the results mentioned above it is reasonable to think that the deep acceptor level of Ev+0.72eV obtained in ODLTS spectrum should be attributed to the acceptor related to Cu-R center.The value of Ev+0.72eV is in good agreement with that measured by Grimmeiss using thermally stimulated capacitance method.Fig.4 shows the ODLTS spectra in Cu-doped and undoped ZnSe crystals heated in N2 atmosphere at 400℃ for 20min.Comparing Cu-doped and undoped ZnSe crystals,it is found that the concentration of Ev+0.30eV remarkably increases and the concentration of Ev+0.72eV also increases for the Cu-doped ZnSe crystal.Fig.5 shows that the concentrations of all deep levels except Ec-0.33eV decrease with increasing the reverse bias.Fig.6 shows the electroluminescence spectra at RT and LNT in Cu-doped ZnSe diffussed at low temperature.In EL spectrum at 77K,there is a strong green emission band peaked at 5300Åbesides the near band edge emission.Two emission bands peaked at 6350Åand 4650Åare appeared in the EL spectrum at RT.The peak position of the red and green bands are similar to that of the Cu-R and Cu-G centers reported by Stringfellow,respectively.Fig.7 shows that the spectra of green band in ZnSe:Cu crystals do not shift with decay time.It indicates that the recombination process of the green band ascribes to non D-A pair transition.According to above results,it may be considered that the deep acceptor level of Ev+0.30eV obtained in ODLTS spectrum should be attributed to the acceptor related to Cu-G center.129|57|0更新时间：2020-08-11
- 摘要：Ce-Mn activated calcium fluorophosphate(FAP:Ce,Mn),as a new kind of yellow phosphor with high efficiency,which is promising in two-component blend lamp,has been prepared resently.Ce3+ was compensated in charge by additional Na+ in this material,lead to a high lumen decay on lamps.In this paper,a sort of high efficient FAP:Ce,Mn phosphor without Na+(Ce3+ is compensated by excessive F-)is reported.The synthesis condition of this material is described,and the formation mechanism of this material is analysed.The firing temperature dependence of lumen efficiency of this phosphor in three types of different atmosphere is shown in Fig.1.It can be seen that the reducing atmosphere is favourable for the formation of high efficient phosphor and that the optimum firing temperature is 900℃.The effect of initial component on the lumen efficiency and lumen maintenance is studied and shown in Fig.2-7.The following results are obtained from these experiments.(1)The effect of the ratio of MM/MP in initial component on lumen efficiency of FAP:Ce,Mn is not obvious,but that on lumen maintanence is striking.The phosphor with the best lumen maintenance can be prepared while the ratio of MM/MP is about 1.64.(2)The emission peaks of both Ce3+ amd Mn2+ shift to short wavelength if the amount of fluorine in initial component incresses.The most efficient phosphor can be prepared only one excessive fluorine,exists and the optimum ratio of MM/MP is 2:3(in excess of 100% in stoichiom-etric composition).(3)The phosphor of FAP:Ce,Mn with Na+ as compensator can give slightly higher initial lumen efficiency,but its lumen decay is more rapid than that without Na+.Considering the requirement in the application of lamp,the phosphor without Na+ is more advantageous.111|72|0更新时间：2020-08-11
- 摘要：A few fluorescein derivatives including bromo-and iodo-derivaties were synthesized.Their fluorescence was measured under the action of lipase,which was extracted from the liver cancer of white mice.The relative fluorescent intensity versus their molecular structure were discussed.The influences of pH value and temperature on decomposition of fluorescein derivatives by lipase were also studied.116|75|0更新时间：2020-08-11
- 摘要：The phenomena of the sensitizing of the carotennora(Car)to the fluorescence of chlorophyll a(Chla)were studied at room temperature.The efficiency of energy transmission and the type of interaction between Car and Chla were estimated in this work.152|71|0更新时间：2020-08-11
- 摘要：In order to descript relations between mean diameter of phosphor powder and particle size distribution function or frequency percentage,the following mathematical model has been proposed.98|81|0更新时间：2020-08-11
- 摘要：The factors affecting performance characteristics of GaAs/GaAlAs double heterostructure edge emitting LEDs(DH-ELED)are described in this paper.Among them,the effect of doping concentration and doping type in the active region on optical power and modulation capacity of DH-ELED is discussed with emphasis.Investigated results show that the ELEDs doped with Si or lightly doped with Ge have higher power and lower frequency response,These LEDs can only be used for the systems of low data rate and higher power.The devices heavily doped with Ge can lead to fast frequency response and lower power.Such a LED can be used for the systems of higher data rate(34.368Mb/s).We can achieve both high power and fast response by means of the reasonable option of doping level.116|63|0更新时间：2020-08-11
- 摘要：By fluorescence decay measurements,physicists,chemists and biologists can study the behaviour of numerous excited species whose lifetimes range typically from 10-6 to 10-9 second.With the related technique of time-resolved emission spectroscopy,an emission spectrum can be recorded in a few nanoseconds after excitation and observed the changes in the spectra with time.These measurements have been carried out from microsecond to picosecond time scale by the use of the single photon counting technique.119|75|0更新时间：2020-08-11
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