最新刊期
卷 6 ， 期 2 ， 1985
- 摘要：For the low-speed electrons,moving along the chains of quasi-one-dimensional polymers, the polymers can be regarded as continuous media. In this paper,a continuons model of mixer dimension (Wilson 1982)is adopted and the interaction of a one-dimensional electron with three-dimensional phonons via deformation potential is discussed. The Hamiltonian of electron-phonon system is
the un-perturbed ground state is 1/√L1 ei q|0>(in perturbation method)and trial wavefunction |ψ>=U1U2|0>(in LLP method). In the weak coupling (with perturbation method)and intermediate coupling(with LLP method)cases,the analytic formulas of ground state energy of the polaron are presented. The self-energy of the polaron 
. The result indicates that thelongitudinal deformation potential is contributed to form the bound state of electron, but the effect of the cross deformation potential quite the contrary For general polymers,a, (longitudinal coupling constant) >>a1 (cross coupling constant),therefore the stable polaron can be formed in the mixed dimensional model. 120|49|0更新时间：2020-08-11 - 摘要：The facilities incorporated in a specially designed horizontal SEM system allows the measurement of both steady state intensity and decay features of cathodoluminescence (CL) in terms of photon count. The sample temperature is controlled via a liquid nitrogen finger Deep level CL bands from n-type GaAs were investigated by using above facilities. The measured features were temperature quenching and excitation dependence of the CL intensity as well as the CL transient Sample. I was a n-type MOCVD GaAs layer with sulphur doped After Cr diffusin at 800℃, sample Ⅰ became sample Ⅱ Although both samples had two main CL bands around 1.2 and 1.0 eV, their positions shifted and their behaviors were quite different. In this work, band A peaked at about 1.15 eV from sample I and band A* peaked at about 1.26 eV from sample I we’re measured. It was found that band A had an approximate single exponential decay behavior and band A* hada double exponential decay behavior For the purpose of theoretically understanding the experimental results, we developed a complete dynamic analysis of deep level luminescence in heavily doped n-type gallium arsenide, based on two different models ’single level model and double levle model. The former implies that the luminescence originates from a free-to-bound transition, the latter implies a transition between the excited state and the ground state of a deep center. Careful derivation shows that the two models give different behaviors of luminescence intensity and decay time Comparing with the actual experimental results, the double level model is favourable Especially, a possible configurational coordinate figure is given to describe the transition associated with band A* The conclusion is that the properties of band A and band A* are completely different Our results support the suggestion that band A is associated with gallium vacancy and band A is caused by chromium atom replacing the vacancy.112|77|0更新时间：2020-08-11
- 摘要：Compared to a large number of works on time evolution of the donor fluorescence[1-7], little has been done on that of accepter [trap] fluorescence in energy transfer study Recently, Huber presented theoretical expressions of time development of accepter fluorescence for static and fast D-D transfer models under the condition CA <<1[8]. In this paper, we have arrived at similar conclusion via an alternative method The distribution function of D-A transfer rates is used.The result derived in this way for static model is an extension of the Huber’s. The decay of donor can be expressed as[6]F(t)=exp(-λt)f(t),where γ is transition rate of donor in the system without accepter, f(t) is related only with D-D and D-A transfer For static and fast D-D transfer, the distribution function of D-A transfer rates, φ, is independent of time.105|86|0更新时间：2020-08-11
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THE EFFECT OF HEAT TREATMENT FOR SUBSTRATE ZnSe IN VACUUM ON ELECTROLUMI-NESCENSE OF ZnSe MIS DIODES
摘要：There is a considerable interest in blue electroluminescence (EL) emitted by MIS diodes of ZnSe operated in forward-bias[1-4].Recently it was reported[4] that the homogeneity of blue EL has been improved. In this paper it is reported that the effect of heat treatment for substrate ZnSe during fabricating an insulating layer in vacuum on EL of ZnSe MIS diodes Nominally undoped ZnSe crystal; grown in this laboratory [6], were used in this study The boule crystals were grown using the method described by Cutter and Woods[5] Dice with dimensions of 3×3×1.2mm3 were cut from the boules, and heated in molten zinc to reduce their resistivities. They were then polished and etched in bromine in methanol,it was followed that an oh-mic contact was made to one of the large area faces with a pellet of indium. A thick (500-1000Å) insulating layer of ZnSe was deposited on the opposite face by the evaporation heated by electron beam, during heating or not heating the substrate ZnSe Finally a circular gold electrode was evaporated on top of the ZnSe film EL emission spectra in forward-biased ZnSe MIS diodes were measured using a Model 44W spectrometer. Fig.1 and 2 showed EL emission spectra in ZnSe MIS diode at RT and LNT, respectively, when the substrate ZnSe was not (curve 1) and was heated (curve 2) during fabricating an insulating layer of ZnSe polycrystal. It was found that two deep center luminescence bands peaked at 6320A and 5350A appeared in EL emission spectra, when a substrate ZnSe was heated during the deposition of the insulating layer Fig.3 and 4 showed EL emission spectra in Cu-doped ZnSe MIS diodes. In comparing the EL emission spectra from the ZnSe MIS diodes with that from the Cu-doped ZnSe MIS diodes, it was obvious that two deep center luminescence bands peaked at 6320Å and 5350Å could be attributed to copper-red (Cu-R) and copper-green (Cu-G) centers of luminescence in ZnSe[7,8]. It was reported that[7,10] as for the atomic nature of centers, the Cu-R center was due to the donor-acceptor pair which was responsible for a substi-tutional copper ion(CuZn+)and a donorlike level of coactivator and the Cu-G center was responsible for an association of a substitutional coppor ion(CuZn+) with an interstitial copper ion (CuI+). Therefore both Cu-R and Cu-G centers included CuZn+ and Cu-G center Contained more amount of copper than Cu-R center Since purification of Ⅱ-Ⅵ compound semiconductors by firing treatment in molten zinc has been reported by Aven and Woodbury[11] . This method has also been applied to ZnSe crystal in order to eliminate Zn vacancies and Cu impurities and reduce resistivities of ZnSe crystal However this firing treatment in molten zinc can not effectively remove residual copper impurity from ZnSe[12]. The ZnSe MIS diodes, in which EL emission spectra contained the blue band only, did not include the copper centers of luminescence If the ZnSe dice were heated in vacuum,the Cu-G and Cu-R bands appeared in EL emission spectra. The results mean that although there were no copper center of luminescence in the ZnSe dice before heating the ZnSe dice, but copper impurity still existed in the ZnSe dice. When the ZnSe dice were heated in vacuum,zinc vacancies were formed on the surface of ZnSe dice due to Zn out diffusion, at same time residual copper impurity diffused into zinc vacancies and formed CuZn+. Thus it is possible to form Cu-R and Cu-G centers of luminescence. Fig.5 showed an insulating layer could be formed on the surface of ZnSe by heating the ZnSe dice in vacuum. It means that Zn vacancies could be produced by heating ZnSe dice in vacuum As the copper impurities diffused into Zn vacancies of the ZnSe dice and formed the copper center of luminescence during the deposition, the EL emitted from copper centers should be depended on both heating temperature and time. The observations shown in Fig 6 and 7 support this point of view. The ratio of luminescent intensity of blue band to that of copper centers of luminescence reduced with increasing heating temperature and time.103|73|0更新时间：2020-08-11 - 摘要：In recent years, the measurement of fluorescence lifetime, decay function and time resolved spectra have made an increasing contribution to the understanding of rapid processes in physical, Chemical and biological sciences. These measurements carried out on microsecond to picosecond time scale, it requires using the single photon counting technique. The decay functions are analysed using numerical convolution and devolution. The experimental data are fitted to preselected kinetic models using rigorous statistical methods. Based on the model SP-70 nanosecond fluorescence spectrometer, this paper disscusses data analysis of fluorescence lifetime, convolution mathematical expression, statistical tests to judge the quality of the results and deconvoluti-on treatment of nanosecond fluorescence lifetime.163|126|0更新时间：2020-08-11
- 摘要：An epitaxial growth of ZnSe single crystalline layer on a GaAs substrate has been performed in a hydrogen flow system using ZnSe powder as source material Before deposition, machemically polished (100) GaAs substrate is first cleaned in trichroethylene, then in aceton and finally in methanol followed by a rinse in deionized water. The substrate is then etched in a mixture of H2SO4:H2>O2:H2O=3:1:1 for about 1 min In order to remove surface damage resulting from cutting and polishing of the wafer. The source material and freshly etched substrate are inserted into the respective zones of the reaction tube. The flow rate of the carrier gas H2 is set to 10-40 ml/min, which is controlled by a mass flow controller (M.F.). The source temperature is about 820-850℃. The single-crystalline ZnSe layer is obtained successfully at the substrate temperature range of 550-750℃. The X-ray diffraction analysis, X-ray Laue pattern and reflective electron diffraction analysis of the as-grown layer demonstrat that the layers are single crystalline and have cubic structure. The as-grown surface microphoto-graph and cleavage edge view are presented. The growth rate is found to be proportional to exp(-EA/kT) in the temperature range of 550-700℃, where k is Boltzmann constant, Ea the activation energy and T the growth temperature The activation energy is 10.5 kcal/mol, which suggests the growth kinetics should be between the mass transfer control case and surface reaction control case. The photoluminescence of epitaxial film is excited by a nitrogen laser (λ=3371Å) with the peak pulsed power of 900kW and measured at 77K and at the room temperature. The PL spectrum at 77K consists of a narrow near-band-edge emission at about 4460Å. A and a broad emission at longer wavelengths which is attributed to Cu-G emission. The presence of this intrinsic near-band-gap emission line in the PL spectrum even at room temperature sbows the bigh quality of the epitaxial layer. The measurement cf the resistivity and Hall effect are made for epilayers of ZnSe frown on a se-mi-insulating GaAs substrate at room temperature. Ohmic contacts to the ZnSe layers are made by In followed by an annealing step in N2 atmosphere at 350℃ for 3 mins. The resistivity of the as-grown ZnSe is typically 1.1Ω·cm.This is attributed to autodoping of Ga impurity from GaAs substrate. The mobility is 114 cm2V-1s-1, and the electron concentration n=5×1016cm-3.It is shown that ZnSe epilayer grown on (100) GaAs by VPE can be a suitable material for blue-emitting electroluminescent devices.142|65|0更新时间：2020-08-11
- 摘要：This paper reports the study on making functional molecular monolayer assemblies by means of Langmuir-Blodgett technique and discusses energy transfer from the donor to the acceptor monolayers. There appears J-aggregate in the mixed monolayer of the NN’-dioctade-cyloxacyanine and hexadecane with the molar ratio of dye:hexadecane=1:1. The J-aggregate state,in fact,is an exciton state and it is possible that there is exciton transfer. This consideration leads to the conception of a functional unit of different components combining energy transfer processes. The structures of the assembled systems are shown in Fig.4. The mixed monolayer L-B assemblies of NN’-ditadecyloxacyanine as donor and NN’-dioctadecyloxacarbocyanine as acceptor are constructed into the energy transfer systems, (a) L-B monolayer assembly of the oxacyanine(molar ratio of dye:hexadecane=1:1).(b)L-B monolayer of the oxacarbocyanine as acceptor (molar ratio of dye:hexadecane=1:1) covers on the assembly of the oxacyanine as donor. The molecular chromophores of the two layers contact each other. (c) The monolayers of donor and acceptor are separated by two monolayers of stearic acid. The distance between donor and acceptor molecules is about 50Å (d) The donor monolayer and the acceptor monolayer are separated by four stearic acid monolayers in the same way. (e) The stearic acid sandwich assembley is six layers. Thefive systems are irradiated by 366nm ultraviolet ray respectively System (a) gives blue fluorescence of the oxacyanine molecules Systems(b), (c), (d) give green fluorescence of the acceptor with the intensities(b)>(c)>(d). In addi tion, part of the emission of system(d) is the blue fluorescence. System(e) does not show green fluorescence,only the blue fluorescence of the donor is observed. The result of above-mentioned experiments shows that the energy transfer between L-B functional monolayers is with Förster radiationless energy transfer mechanism.125|80|0更新时间：2020-08-11
- 摘要：One approach to the utilization of solar energy is the development of devices that mimic natural photosynthesis. Such artificial photosynthesis efforts would be aided by a better understanding of the primary photochemical steps that occur in the natural process of photosynthesis. As a result our studies emphasize the mechanistic and structural detial of photosynthetic antenna system this appears to be crucial to the design of artificial solar energy devices. Chlorophyll a (Chl-a) has long been known as the major light-absorbing pigment in photosynthetic antenna systems Furthermore, the light absorbed by some carotenoides (accessory pigments) is photosynthesis active. The accessory pigments can transfer their absorbed energy to Chl-a Energy transfer has been considered the mechanism by Förster In types of artificial mono-layers,Chl-a and carotene (Car) are isolated from spinach in the usual manner of extraction followed by purification by column chromatography. In order to investigate the interaction between Chl-a and Car in a monolayer assembly, attempts are made to build up two different types of assembly on glass plate by conventional Langmuir-Blodgett techniques. One type is a monolayer film consisting of Chl-a and octadecoic acid with molar ratio of 1:10. As the artificial molecular monolayer of Chl-a forms aggregates, its fluorescence spectrum has a main peak at 677nm and a secondary peak at around 766nm(Fig.1). The main peak of Chl-a luminescence in the monolayer is shifted by 16nm to the long-wave band when compared with its state in the solution. This shift is apparently due to an increase of aggregate forms in the monolayer with respect to the solution. A new maximum (766nm) appears in the Chl-a fluorescence spectrum. It is due to the aggregate form of pigment The other type is a Car-Chl-a mixed monolayers with molar ratio 5:l;50:l;and 125:1 The two bands all appear in the cases of Car as donor and Chl-a as acceptor And then the luminescence intensities have nonlinear decay with the decrease of Chl-a molecule (Fig.2). The general idea is that Car helps the artificial antenna system to catch more of the incident light energy because they can take up excited light. The accessory pigments can transfer their absorbed energy to Chl-a Experiments show that the limited Förster transfer distance is about 100Å But as a result of the cooperation of exciton transfer and Förster transfer, the distance increaces. The result suggests that exciton transfer should play an important role in luminescence of biomimetic pigment films.102|60|0更新时间：2020-08-11
- 摘要：The chlorophyll in non-polar solvent could aggregated into dimer or polymers. The aggregated chlorophyll in petroleum ether (mainly polymers) could emit faint light for a few minutes after illumination. The decay curves of the delay light emission (DLE) showed two phases:fast phase which lasted for about ten seconds and slow phase which lasted for about several minutes. The intensity of the fast phase would increase slightly when the illumination time was sustained more than one minute, while the intensity of slow phase would increase continuously, The decay curves of the DLE of aggregated chlorophyll in CC14 (mainly dimers) was different from that in petroleum ether:the intensity of the slow phase was reduced obviously, while the intensity of the fast phase was as same as that in petroleum ether. The intensity of the DLE was lowered by adding electronic donor or accepter When the aggregated chlorophyll was disaggregated, there was no DLE. It was evident that light energy could store up in the molecules of chlorophyll aggregates.95|68|0更新时间：2020-08-11
- 摘要：The GalnAsP/InP DH-LEDs,which emit the light in 0.96-1.67μm spectral range, have been used in optical communication. In this paper, we report the fabrication of 1.3μm GalnAsP/InP LED with lens using chemical etching in detail. This lensed LED improves the coupling efficiency and the external quantum efficiency. The InP substrates used were (001) oriented or other oriented n-InP single crystal slices (Sn-doped,n-7×1017-2×1018cm-3). The GalnAsP/InP DH wafers were obtained by successive LPE growths of 5μm thick n-type buffer layer,an undoped GalnAsP (A-1.3μm) active layer and 1 urn thick p-type (Zn-doped) confining layer.110|51|0更新时间：2020-08-11
- 摘要：Luminescence of aromatic molecules is vary important in organolumines-cence. In this paper, it is simply introduced to calculate the absorption and fluorescence spectra of aromatic molecules by using quantum chemistry methods. Relationships between the luminescence behaviour and the structure of aromatic molecules are described Energy transfer and migration in organic systems are discussed in detail. The spectrum investigation of aromatic molecules using quantum chemistry methods involves Huckel’s molecule orbital theory (LCAO-MO), Platt’s perimeter free-electron orbital calculations (PFEO) and Pariser-Parr-Pople calculations (PPP) Luminescence behaviour of aromatic molecules is closely related to their structure such as bonds, planeness, rigidity and size of molecules and substituted aromatic compounds Energy transfer and migration in organic systems involve the radiation transfer, dipole-dipole resonance transfer, exciton diffusion, diffusion-controll process and electron transfer process. It is suggested recently that the process of excimer formation and dissociation should be also a kind of energy transfer.111|67|0更新时间：2020-08-11
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