最新刊期
卷 13 ， 期 4 ， 1992
- 摘要：Porous silicon samples were prepared by electrochemical etching in HF-C2H5OH solution. Polished n type and p type (111) Si wafers with resistivities of 40-60Ω·cm, and 8-10Ω·cm, respectively, were used as substrates. A contact was made to the back of the wafer, which served as the anode and Pt as cathode. The typical etching current was 1-10mA.The samples show intense red colour luminescence excited by UV light or 488nm lino from Ar ion laser at room temperature. The PL band is rather broad with the full width at half maximum of about 0.31eV. The peak wavelength shifts from 770nm to 730nm as the etching time increases from one hour to 6 hours, keeping the etching current at 2mA. While increasing the current to 10mA, the peak position further shifts to 670nm. Such a large blue shift has also been observed when increasing measurement temperature. Infrared spectra show that there are Si-H, bond vibration absorptions at 2080-2100cm-1. 850-900cm-1 and 640cm-1 corresponding to the stretching, bending and wagging modes, respectively. Besides Si-Hn bondings in porous Si, Si-F and Si-O bondings at 830cm-1 and 1070-1120cm-1, respectively, have also observed and the relative content of F and O atoms increases with the etching current.The structure of porous silicon consists of nanometre size and micrometer deep silicon columns produced by electrochemical ething. The visible luminescence in porous silicon is attributed to the radiative recombination of excitons confined at the quantum wires. The incorporation of H and F atoms in the sampler is considered as the terminatinators of the dangling bonds at the surfaces of the silicon wires, and may play an important role in keeping a high intense visible PL. Extending etching time or increasing oxygen content would thin the quantum wire, resulting in the blue shift of the PL spectra.143|75|4更新时间：2020-08-11
- 摘要：Eu(MFA)3bpy (MFA: p-methoxybenzoyl-furoylmethane, bpy: 2,2'-bipyridine) complex was synthesized and characterised by elementaryanalysis,IR,Raman and HNMR spectra.At 77K,excitation and emissionspectra were recorded.Spectral data show that the complex is composedof the two similar Eu(Ⅲ)sites with G2v symmetry.107|39|0更新时间：2020-08-11
- 摘要：In low energy electron luminescence, the electron accumulation and nonradiative recombination on the surface of phosphors is one of the main resistance in developing vacuum fluorescent display (VFD) devices. Y2O2S:Eu,ZnS:Cu, Al and ZnS:Ag are used as a kind of three-primary phosphor, excited by 400~lkeV electrons in color VFDs with the luminous efficience of R:2.61m/W, G:10.21m/W and B: 1.71m/W by 1keV excitation. In order to obtain the device with low threshold voltage and high luminous efficiency, a very thin phosphor layer is applied.To fit this three-primary phosphor for VFD, a special structure of display device is designed. This device has the following characters: (1) a tetrode structure with two layers of wire-shaped grid, so that the device can be addressed with low driving voltage by ICs; (2) a front luminous type, to widen the viewing angle; (3) a set of cathode with two spiral ends, to reduce the cold end from the length of more than 5mm to about 1mm.Based on above discussion, we developed a vacuum fluorescent display device with twelve color phosphors printed in a format of 10(column)×12(row) and operated at the anode voltage of 500V.In each column, there are 12 colors. They are pink, red, reddish orange, orange,yellowish orange, yellow, green, bluish green, blue green,greenish blue,blue and purple. This device can be used in a Hi-Fi audio system for spectrum display.106|105|2更新时间：2020-08-11
- 摘要：The near-band emission mechanisms and deep levels of pure green LED has been studied from 77K to room temperature.The samples were fabricated by an overcompensation liquid phase epitaxy method.The peak wavelength of LEDs at 300K was 555nm. Experimental evidences are presented to the emission of dominating centers at 77K, originating from D-A pair transition. When decay time increases, peaks shift apparently toward low energy as a consequence of the distance dependence of the Coulomb interaction. Also, exciton transitions were observed at 77K and the free-exciton recombination did not decay-exponentially. So that it becomes the dominant emission mechanism at room temperature.The near-infrared electroluminescence spectra of N-free GaP LED are complicated. Three overlapping broad emission; bands were observed and decomposed. Their spectra fit Gaussian line shapes and peak energies are 1080nm(1.15eV), 1260nm(0.98eV)and l510nm(0.82eV), respectively. The 1080nm and 1510nm bands are related to the presence of oxygen and 1260nm band is associated with different recombination processes, involving the PGa antisite defect.120|58|0更新时间：2020-08-11
- 摘要：Both the ray tracing algorithm and the general solution of geodesic lens were used to design the meridional curves of spherical-aberration-free aspherical lens.The single point diamond machining and a technology for fabricating depression waveguide were used to fabricate the geo- desic lenses in LiNbO3. The lens aperture and effective aperture are 8 and 6mm, respectively. The experiments show that the lens is spherical-aberration-free in the range of 6mm effective aperture, the diffractive spot size is 4μm for input beam of 4mm width and the lens insertion loss is about 1dB.108|53|9更新时间：2020-08-11
- 摘要：ZnSe is a direct-gap Semiconductor with the zinc-blende crystal structure and a relatively large band-gap energy of 2.7eV at 300K. Excitons in ZnSe are strongly bound with a binding energy of ~20meV. Recently, attention has been paid to the strained layer quantum well using a ZnSe layer as the well material, which provides the possibility to obtain excitonic emission and optical bistability (OB).The growth of ZnSe-ZnS MQWs with steep interface and narrow well have an important significance for studying quantum size effect, subband transition and carrier scattering. Taike et al.[2] has reported the growth of ZnSe-ZnS SLS with well thickness (Lw) of ~0.5nm by MBE. But the PL peak position is about 430nm which is not agreed with the result calculated by Kroning-Penney model. In this paper, we report, for the first time, the preparation of narrow well ZnSe-ZnS MQWs with well Thickness(Lw) of ~0.5nm and the excitonic peak blue shift to 375nm (3.304eV). X-ray diffraction shows the ZnSe-ZnS with good quality periodic structure. The excitonic peak in PL spectrum shifts towards higher energy side as the well thickness reducing, indicating the quantum size effect of the ZnSe-ZnS MQWs.96|127|2更新时间：2020-08-11
- 摘要：Two distinct configurations, F-(CN)- and :F-(NC)-, of the ground state of FH(CN)- defect pair in CsCl crystal have been studied by the self-consistent calculation with extended-ion method. It is shown that F-(NC)- is the more likely occupied configuration in the crystal, in contrast to the conclusion of Crash. The energy-configuration adiabatic energy curves of the FH(CN)- defect pair are calculated in the ground state and excited state respectively. The reults of the calculation for absorption spectrum are in good agreement with the experiments. For the first time, a study of the mechanism of nonradiative process in this system is reported.104|43|0更新时间：2020-08-11
- 摘要：The properties of exciton in the surface layer of crystals influence the optical properties of the crystals very remarkably. In recent years, many scholars [1-2] discussed the properties of the surface exciton. Most polar crystals are diatomic. In these crystals there is one mode of the longitudinal optical (LO) phonon. However, a large number of polar crystals, with several atoms per unit cell, have more than one LO phonon branch. In recent years the polar on problem with many LO phonon branches has been studied [3-4]. However, the exciton in polyatomic polar crystals has not been investigated so far. The ground state energy of a weak, intermediate and strong coupling exciton in polyatomic polar crystals has been obtained by means of perturbation and linear -combination-operator method by one of authors [5-6]. Recently the effective Hamiltonian of the surface exciton in polyatomic polar crystals was derived by using perturbation method by author[7]. When we consider the interaction between phonons of different wave vector in the recoil process, the influence on effective potential between the electron and the hole, the self-trapping energy and the self-trapping condition are discussed.The Hamiltonian of a polyatomic surface exciton-phonon system is
. We introduce two unitary transformations U1 and U2. 111|66|0更新时间：2020-08-11 - 摘要：The Tb3+-doped calcium, strontium and barium tungstates have been prepared. The emission and excitation spectra were studied. The X-ray powder diffraction data reveals that these compounds are all tetragonal crystals, space group I41/a(C4h6). The lattice parameters are: a=0.5238 and c=1.1364nm for CaWO4:0.01Tb, a=0.5409 and c=1.1941nm for SrWO4:0.01Tb, and a=0,5611, c=1.2712nm for BaWO4:0.01Tb. The alka-liearth metal atoms are coordinated with eight oxygen atoms.In these compounds, the Tb3+ ion substitutes the site of alkali-earth metal ion and does not occupy a site with a centre of symmetry, and shows relatively strong emissions of 5D3→7F6, 7F6, 7F4 and 5D4→7F6, 7F5 transitions, and the weaker emission of 5D3→7F3, 7F2 and 5D4→7F3, 7F4 transitions under excitation with 254nm radiation. There are four types of excited state to produce 5D4→7Fi emissions: (a) the excited state of O2-(2p)→W6+(5d) charge-transfer in tungstate groups (the excitation energy can be transferred from the host lattice to the 5D4 energy level of Tb3+ ion), (b) that of O2-(2p)→Tb3+(4f) charge-transfer, (c) that of 4f8→4f75d transition of Tb3+ ion and (d) 4f→4f transition of Tb3+ ion. In the case of 5D3→7Fi emission, the excited state only has three types of (b), (c) and (d). The excitation energy levels of (a) can not be transfered to energy levels of 5D3 and above.97|66|9更新时间：2020-08-11
- 摘要：Cd2SnO4 thin films are a n-type wide-bandgap semiconductor. Thin films of the teinary oxide Cd2SnO4 show the remarkable properties such as low, metal-like electrical resistivity, good transmissivity in the visible range of the light spectrum and high reflectivity in the near IR[1-6]. These films can be used transparent electrodes, heat mirrors and antistatic layers in optoelectronics and solar enrgy conversion technology.In this paper we report the photoluminescence properties of Cd2SnO4 thin films prepared by r.f. reactive sputtering from a Cd-Sn alloy target in an Ar-O2 reactive gas mixture. Experimental results show that the photoluminescence spectrum of Cd2SnO4thin films is very sensitive to the deposition conditions. The photoluminescence peaks exhibit a‘red shift’when oxygen concentration is increased. The variation of emission peaks of Cd2SnO4 thin films may be attributed to the change of oxygen vacancy in Cd2SnO4 thin films. Cd2SnO4 thin films are a n-type defect semiconductor in which oxygen vacancies are believed to provide the donor state [9,10]. The oxygen vacancy concentration can be varied over a wide range with the change of oxygen concentration during deposition. The free carrier concentration of conduction band changes with changing oxygen vacancies. The change of the carrier concentration causes the shift of band gap according to the Burstein-Moss (BM) effect[12,13] and the effect of electron-electron and electron-impurity scattering[14]. Then, the photoluminescence peaks are shifted with the change of band gap.97|38|2更新时间：2020-08-11
- 摘要：The luminescence characteristics of crystallites of BaCl2:Eu2+, which was prepared by the solid state reductive atmosphere in the box furnace, and BaCl2·2H2O:Eu2+, were studied.The comparison between BaCl2:Eu2+ and BaCl2·2H2O:Eu2+ on emission spectra, excitation spectra, photo-stimulated luminescence (PSL), and thermoluminescence (TL) are reported.The excitation and emission spectra show that both BaCl2:Eu2+ and BaCl2·2H2O:Eu2+ can be excited by the ultraviolet light.At low concentration of Eu2+, both materials can be excited most efficiently by 254nm from a low-pressure mercury lamp. At high concentration of Eu2+, they can also be excited efficiently by 365nm from a high-pressure mercury lamp.94|36|0更新时间：2020-08-11
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EPR STUDY Mn2+ CLUSTER FORMATION IN DCEL ZnS:Mn,Cu AND ITS INFLUENCE ON LUMINESCENCE CHARACTERISTICS
摘要：The EPR speetra. of DCEL ZnS:Mu, Cu vary with the different cal cining temperature T. Simulating the EPR spectra with microcomputer, one can calculate the relative concentration CC/C of Mn2+ clusters. As calcining temperature T grows over 950℃, the CC/C increases with T. We can conclude that formation of Mn2+ clusters is relative to the structural phase. The sixfold lattice (α phase) enhances the spin exchange interaction of Mn2+ ions and accelerates the formation of Mn2+ clusters. The luminescence intensity I decreases with the increasing relative concentration CC/C of Mn2+ clusters.The optimal calcining temperature of DCEL ZnS:Mn, Cu powder is discussed.121|47|2更新时间：2020-08-11 - 摘要：Studies on the structure phase transition and microstructure of ZnS:Cu and ZnS:Mn by X-ray powder diffraction analysis (XPDA), electron spin resonance (ESR) and high resolution electron microscopy (HREM)show that: (A) the phase transition temperature of ZnS is shifted obviously to higher value when the concentration of Cu is greater than 1×10-3 or to lower value when the concentration of Mn is greater than 1×10-3;(B)for ZnS:Cu 2×10-3(calcined at 900℃),there mainly exist 180° rotation twins of β-phase; (C) for ZnS:Mn 5×10-3 (calcined at 900℃)there mainly exists the coherent growth of β-phase (180° rotation twins) and α-phase at micro-area in atomic scale; and (D) twin boundary areas and crystal streaks are rich in Cu.106|54|1更新时间：2020-08-11
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