最新刊期
卷 12 ， 期 3 ， 1991
- 摘要：The growth of ZnSe-ZnTe strained-layer superlattices on CaF2(111) substrate by atmospheric pressure metal organic chemical vapor deposition is reported for the first time. The typical growth conditions are shown in Table 1. The critical thickness of ZnTe/CaF2 heterojuncticn is appraised as 2nm. With X-ray diffraction measurement, we observe many satellites of ZnSe-ZnTe SLS around(333) reflection, which confirms the formation of the period structure of superlattices, and shown in. Fig.1.The lattice parameters of ZnTe, Zr.Se and CaF2 are 0.6101 nm, 0.56686 nm, 0.54626 nm, corresponding to the Bragg diffraction angles 29 around (333) reflection 82.00, 89.837 and 94.231 degree,respectively. We found that the satellites around the ZnSe Bragg angle are very strong, while the satellites around ZnTe Brafg argle are too weak to observe them in Fig.1. So the thickness of ZnSe layers is much larger than that of ZnTe layers.Using the zero-order peak corresponding to the average perpendicular lattice parameter and the superlattice periodicity calculation, we obtain the data of ZnSe and ZnTe layers a.s 6nm, 0.6nm, respectively.For ZnSe (6nm)-ZnTe(0.6nm) SLS/CaF2 (111), the first ZnTe layer on substrate CaF2 can not be accommodated by elastic deformation, and the lattice constant of the SLS parallel to the surface determined by Eq.1 does not equal the lattice constant of the substrate.Fig.2 is the photoluminescence emission spectrum of ZnSe (6nm)-ZnTe(0.6nm) SLS/CaF2 with the excitation of the line 337.1nm of N2-laser at 77K. The peak value is 630nm which shows the existence of strain and quantum confinement effects. Fig.3 is the optical absorption spectrum of ZnSe(6nm)-ZnTe(0.6nm) SLS on CaF2 transparent substrate with the measurement of UV-3000 Double Wave-length/Dual Beam Recording Spectrophotometer at room temperature. The first absorption peak at 640nm is thought to be the optical absorption due to the transition Between the n=1 electronic subband in ZnSe layers and the n=1 heavy hole subband in ZnTe layers.116|38|0更新时间：2020-08-11
- 摘要：The sharp luminescence of n-Si(As):Yb at 1130nm is reported for the first time in this paper. Its half width is 23.2nm. The three weak peaks with wavelength of 1190nm(1.04eV), 1150nm(1.08eV) and 1100nm (1.13eV), respectively, are also observed at the same time. However, the both peaks at 1190nm and 1100nm are observed only when the light signal is amplified. We think that the three lines are the phonon replicas.The experimental results demonstrate that the emission intensity at 1130nm increases with increasing Yb dose. For lower dopar.t ones, especially, the intensity is significantly increased with slightly increasing Yb dose. For the range of ion number between 5×1012 to 1×1013, the intensity is almostly proportional to Yb dose. The intersily increasing becomes gradual when Yb exceedes 1×1013 ions cm-2.In order to find the emission evidence, the absorption and tramsmi-ssion spectra (ATS) for the host and the luminescent samples were measured, respectively. Due to having no similar data previously, therefore, ATS oi n-Si(As):Er is shown for comparison to n-Se(As):Yb. Via an analysis we concluded that:the emission at 1130nm in n-Si(As):Yb does not arise from Si bandside; the excited energy of He-Ne laser (632.8nm) is not decrectly absorbed by As impurity in Si; and it does not arise from the radiative transition 2F5/2-2F7/2 of Yb3+ (4f13).Finally, we think that the emission is a result of both sensitizer Yb and activator As. Here Yb acts as a shallow acceptor and is in the vicinity of top of valent band in Si. The energy transfer procedure between Yb and As are discussed, and a four level luminescent mode is proposed. It is found that the luminescent efficiency can be improved by appropriate selection of concentration ratios between Yb and As.103|53|0更新时间：2020-08-11
- 摘要：The high purity and high quality CdTe single crystals were grown by the sublimation method either under excess Te of less than 0.02% or not.In this paper, the holographic phase-contrast microphotography is introduced to the research of high temperature growth of single crystal for the first time. The growth ampoul and furnace with parallel windows were designed.The principle of this technique was discussed and the efforts were made to obtain the experiment conditions for best results. Three-dimensional observing and. recording of the growth process in real time were obtained, and an accuracy of 3.9μm was achieved.The boundary layers were recorded under both growth and dissolution processes as well as various superaturation ΔT, which is the temperature differ onee between crystal and source. The results suggested that the absorption layer become thicker with, the ΔT increasing.112|51|0更新时间：2020-08-11
- 摘要：Four angular overlap parameters eσ、eπ、eδ and eφ for Eu3+ ions in LaOX (X=Cl,Br,I) crystals for which the approximative point group symmetry is C4, have been calculated for the first time by making use of Angular Overlap Model(AOM). And the energy levels were fitted. The angulap overlar parameters obtained are listed in Table 2. From this we can see that the values of parameter eσ which describes the an-tibonding effect a decrease with the increasing atomic number, that is, the order of ligands is Cl,Br,I. The order is Cl, I, Br for parameter eπ. Four angular overlap parameters are all larger for ligand Cl than for corresponding ligands Br and I. From this result we can draw a conclusion that the possibility of covalency between 4f electron and ligand is somewhat larger than the other two compounds. But there is no predo-minant order of covalency between ligands Br and I. Parameters eδ and eφ also have significant contribution to the energy-level splitting and shifting. Errors will occur if we neglect them. In our calculations, the reasons for large deviation are as follows.1. Deviation of free-ion energy le els. Because we adopt the average value of experimental energy levels as the value of free-ion energy levels. For Eu3+ ions, the spectral structure is very complicated, especially for 7F5 and 7F6. The assignment of energy levels is very difficult. Hence, the error of experimental energy levels can influence the results of calculation.2. A few parameters can also cause the deviation.3. As for Eu3+:LaOX(X=Cl,Br,I) series, oxygen is also a kind of ligand besides Cl, Br and I. In our calculations we assume that the charge of all ligands is equal.In Tables 3,4, and 5, the energy levels obtained from our calculations are given, compared with experimentals. The assignments of Irreducible Representation(I.R.)are ours. They have a little difference with those of experiments (see References[10,11]).106|84|0更新时间：2020-08-11
- 摘要：The long persistence phosphor of Mg3Bo3F3:Mn2+ doped with rare earth ions R3+ (Eu3+,Sm3+ and Dy3+)was synthesized by solid-state reaction at 1100℃. The optimum concentrations ot R3+ for preparating samples were examined. The cathodoluminescence propertiers of the longer persistence (τ=210ms) phosphors Mg3Eo3F3:Mn2+,R3+ were investigated.It is found that Eu3+ and Sm3+ ions affect the emission spectrum and color coordinates of Mg3Bo3F3:Mn2+ phosphor. The narrow emissions ot Eu3+ and Sm3+ ions overlap on a broad emission band of Mn2+ ion in these phosphors. From Fig.3 and Fig.4 it can be seen that the narrow emissions of Eu3+ and Sm3+ ions in Mg3Bo3F3:Mn2+ are located at 613nm corresponding to 5D0-7F2 transition of Eu3+ and at 651nm of Sm3+ 4G5/2-6H9/2 transition respectively.The brightness of red Mg3Bo3F3 Mn,R3+ phosphors depends linearly on the acceleration voltage.109|33|0更新时间：2020-08-11
- 摘要：Raman backscattering techniques have been used to measure the phonon spectra of ZnSe-ZnS strained layer superlattices (SLSs) on CaF2 (111) and GaAs (100) substrates grown by atmospheric pressure metal-organic chemical vapor deposition. CaF2 is a transparent substrate for visible region, and is a good substrate for Raman scattering measurement.In part 1 of the paper, we briefly review the development of Raman scattering of semiconductor superlattices. In part 3, we describe the Cerdirs’s theories[2] about the calculation of the frequency of longitudinal optical (LO) phonons and transverse optical (TO) phonons of ZnSe and ZnS layers which are under biaxial stress. With Eq.1, we can calculate the frequencies of LO phonons if the effective spring constants p and q are known. In part 3, it can be observed that the energy of ZnS LO phonon in ZnSe-ZnS SLS on CaF2 is 23cm-1 which is lower than that in bulk ZnS, and the peak is very sharp with dominant strength while the peak of ZnSe LO phonons is very weak in Raman spectra of ZnSe-ZnS SLS on CaF2 (111), shown in Fig.4. In Raman spectra of ZnSc-ZnS SLS on GaAs (100) shown in Fig.3, we found that energy of ZnSe LO phonons in SLS is 35cm-1 which is larger than that in bulk ZnSe, and there is a peak with wave number of 110cm-1. We think that the 110cm-1 peak results from Raman scattering of amorphous Se in the surface of ZnSe-ZnS SLS. In conclusion, the energy of LO phonon of a semiconductor material under biaxial compressive strain will shift towards the blue, while the energy of the LO phonons of a semiconductor material under biaxial expanded strain will shift towards the red. Our experiment spectra agree with the Cerdira’s theories in principle.133|74|1更新时间：2020-08-11
- 摘要：K2NaAlF6:Ce3+and KAlF4:Ce3+phosphors were synthesized by solid state reaction method at Ar atmosphere. Their structures have been determined and the structure parameters calculated. K2NaA1F6:Ce3+belongs to cubic system, space group Fm3mm, aaaaaaaa=0.8112nm. KAlF4:Ce3+belongs to tetragonal system, space group P4/mmm aaaaaaaaa=0.3556nm, c=0.6147nm. The. spectra of K2NaAlF6 =Ce3+ and KAlF:Ce3+ were.measured. According to the characteristic of spectral structure the replaced sites of Ce3+ are discussed. Probably Ce3+ ions replace M+ lattice sites.109|45|4更新时间：2020-08-11
- 摘要：The absorption, fluorescence and excitation spectra of zinc tungsta-te crystals activated by Ce3+, Cu+, Co2+, Ni2+ and Er3+ ions have been measured and studied with SHIMADZU UV-265 visible recording spect-rophotometer and RF-540 spectrofluorephotometer. Results show that most of the activated ions have strong absorption in UV range. When the absorption spectra were measured a thin zinc tungstate was used as the referential crystal instead of air to eliminate the influence of the host lattice because the existence of strong absorption in U.V range.The results obtained from the excitation spectrum measurements are similar to those from the absorption meausrements.The Cu+ ion has strong radiation in visible band (30C-600nm) when excited at 380nm with peak position at 460nm. We are intended to get 300-600nm tunable laser of Cu+ ion in ZnWO4:Cu crystal.109|87|1更新时间：2020-08-11
- 摘要：RE borate glass is a kind of potentially valuable luminescence material.More than twenty types of various borate glass doped with Eu3+ or Bi3+ ions and co-doped with Eu3+ and Bi3+ ions were investigated. The influence of glass composition on. the luminescence of Eu3+ iors and the ssnsitization effect of Bi3+ on Eu3+ ions were also studied.The fluorescence intensity of Eu3+ ions is the strongest when the MmOn is Li2O, MgO or A12O3 in the B2O3-EaO-MmOn glass system (MmOn:Li2O, Na2O, K2O, MgO, CaO, SrO, A12O3, La2O3, Bi2O3), and the fluorescence intensity of Eu3+ ions is the weakest when the MmOn is La2O3. The luminescence emission peaks of Eu3+ ions shift towards longer wavelength with the increase of radius of alkali metal alkaline-earth metal and trivalent metal ions.The optimal concentration of Eu3+ is different in different host glasses.The ions of Bi3+ can sensitize the Eu3+ luminescence, when, sensitized by Bi3+, the emission intensity of Eu3+ is increased by a factor of 1-2.5.101|59|6更新时间：2020-08-11
- 摘要：Na5Eu(MoO4)4 and NaEu(MoO4)2 are stoichiorr.etric host luminescent materials having high concentration of luminescent Eu3+ ions and no noticeable concentration quenching. Raman spectra of these two materials have been studied. The symmetry species of the lattice vibration modes of Na5Eu(MoO4)4 have been analysed by means of the group theory.The structures of both materials belong to tetragonal, I4I/a (C4h6) space group. For Na5Eu(MoO4)4, the free ion symmetries of (MoO4)2-, Eu3+ and Na1+ correlate with factor group C4h through their site groups. A primitive cell includes two Na5Eu(MoO4)4 molecules. It mears that 8 (MoO4)42-, 10 Na1+ and 2 Eu3+ are included in the cell. So the lattice vibration of Na5Eu(MoO4)4 in the cell can be classified into 72 internal modes and 84 external modes. For crystal factor group C4h, the Ag,Bg and Eg modes are Raman active and Au and Eu modes are infrared active.112|57|0更新时间：2020-08-11
- 摘要：Among the most widely investigated devices for Integrated Optics are modulators, switches and spectrum analyzers using Ti-diffused LiNbO3 waveguides. For practical application of such devices the coupling problem of single-mode fibers to single-mode diffused waveguides seems to be one of the most basic and most important problems, To achieve the optimum efficiency in coupling single-mode fibers to single-mode planar waveguides, two conditions must be satisfied:(1) the field distribution of their modes must be matched; and (2) the lateral position between fiber and waveguide must be aligned precisely.An available device with end. fire coupling of single-mode fibers to Ti:LiNbO3 single-mode planar waveguides was designed and fabricated, according to the analysis of coupled mode theory in this paper. To reduce the waist of near-Gaussian beam emitted by fiber, a microlens was formed by arc discharge on the end of single-mode fiber.In this way,the mode distributions of single-mode fiber and single-mode planar waveguide were metched better. In order to achieve precise alignment, two-dimensional silicon V-grooves were used as the positioning alignment frame. The coupling efficiency up to 64% has been measured practically.116|56|0更新时间：2020-08-11
- 摘要：Na5Eu(MoO4)4 is a stoichiometric host luminescent material. If H2WO4 and Na2WO4 are added as reactants in synthetic process of Na5Eu(MoO4)4, the Na5Eu(Mo1-xWxO4)4 system will be synthesised. When 0<x<0.21, the fluorescence spectrum of the system, is almost the same as Na5Eu(MoO4)4 and the intensity of main emission peak is higher than that of latter. The maximal increase is about 30% when x is 0.033. The X-ray powder diffraction analysis shows that when the value of x increases, the ratio of crystal cell parameter c/a decrease. It means that W ions enter into the lattice of Na5Eu(MoO4)4. The reason of enhancement by W might be related to the change of crystal field environment of Eu3+. If SiO2 is added as a reactant in synthesis process of Na5Eu(MoO4)4, when the molar ratio of Si to(Si+Mo), y, in 0<y<0.08, the intensity of main peak will increase and the maximal increase is about 50% when y=0.028. According to X-ray diffraction analysis, the reason of enhancement might be related to alpha cristobe-lite which is formed by added SiO2 and forms the encapsulation of Na5Eu(MoO4)4.97|52|0更新时间：2020-08-11
- 摘要：In this paper the capability to scavenge the
of 17 kinds of Chinese tea by chemiluminesccnce of XO-L system is reported. It is found that the antioxidative activation is different for different kinds of tea. In general, green tea has the highest antioxidization and black tea has the lowwest antioxidization by comparison for green, wulong and black tea. Famous tea has higher antioxdization than normal tea. First-class tea has higher antioxidization than the second-class tea. Some conditions and factors of antioxidization of tea have been determined. All the results suggest that there should be correlation between the antioxidization and the quality and price of tea. 105|84|0更新时间：2020-08-11
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