最新刊期
卷 26 ， 期 4 ， 2005
- 摘要：From the 1980s,our main research results on waveguid grating domain of integrated optics are introduced as follows.The first, we designed and made Lloyd's simple versatile exposure interferometer.In the same installation, it can be formed by adjusting location of column lens to the straight stripe grating of the equal period, the chirped grating or the curve-grating masks on the photoresist, respectively. And then combining with ion or chemical etching technique, the various waveguid grating devices for integrated optics can be fabricated. The set up can also be used to fabricate volume holographic phase Bragg gratings with slant stripe by adjusting (angles) between sample and mirror. This Lloyd's exposure interferometer compared with traditional double-optical path exposure interferometer has the advantages, such as small-sized, versatile, a few of optical elements, shorter optical path, vibration-proof, small angle exposure and so on. So the technique by using Lloyd's exposure to make photoresist grating masks is called "standard technique", ane quoted abroad extensively. Up to now. grating devices have successfully been fabricated on varied waveguide materials, such as semiconductors, glasses, polymers and so on, by Lloyd's exposure and ion etching techinque. The second,some research results of the waveguide grating devices in our group since the year 1988 include: (1)The photoresist grating was made on parabolic coupling horns of channel waveguide with 4 μm width of K+-Na+ ion exchange CdSxSe1-x microcrystal glass to form grating limiter of 12 μJ limited energy threshold. (2) DFB optical bistability device was made on CdSxSe1-x microcrystal glass waveguide with K+-Na+ ion exchange by Lloyd's exposure and ion etching technique to obtain bistability switch time of 63 ps and threshold average powe of 77 mW. So devices operating with super fast rate and lower power loss were realized.(3)Chirped grating was made on K+-Na+ ion exchange CdSxSe1-x microcrystal glass wavequide by ion etching to form optical beam scanner. Maximum change quantity of focus location moving was 80 μm in power density of 1.5×102 W/cm2 by using Ar ion laser of 0.514 5 μm wavelength. (4) Poly-layer ZnS/ZnSe thin film (clading) was alternatirely coated on BK7 glass waveguide of Ag+-Na+ ion exchange to form nonlinear waveguide grating device. Then optical interconnection with dynamic seek position characteristic with 3 cm linear space can be realized. (5) Interconnection coupling devices with volume holographic phase Bragg grating-light guided board were fabricated on photopolymer with red sensitive to form the grating-splitting board with equal intensity and successfully used for optical butterfly interconnection network of computer. (6)Volume (holographic) phase Bragg grating was fabricated on same glass light guided board to form optical interconnection of the spot to the spot with semiconductor laser 0.78 μm. Its potential application for optical interconnection (between) two printed was indicated. (7) Wavelength-division multiplexed device on monolithic integrated waveguide was made and measured to get complete separation of double-wavelength of 0.632 8 μm and 0.785 μm.关键词：optical waveguide;periodic structure;grating coupler;holographic Bragg grating;optical interconnection124|106|1更新时间：2020-08-11
- 摘要：In recent years, with the development of several experimental techniques, for example, metal-organic chemical-vapour deposition, molecular beam epitaxy and electron beam lithography combined with reverse mesa etching, there has been of considerable interest in understanding of hydrogenicimpurity states in low-dimensional semiconductor heterostructures such as quantum wells, quantum wires and quantum dots. Recently, there has been great interest in investigating quantum dots both theoretically and experimentally. Due to the small structures of QD's, some physical properties such as optical and electron transport characteristic are quite different from those of the bulk materials. The study of the impurity states in these low dimensional structures is an important aspect to which many theoretical and experimental works based. Recent investi-(gations) in the reduced dimensionality show that for the impurity within the reduced dimensionality the impurity binding energy will be enhanced with the deduction of the dimensionality.In recent years, the problem of a bound magnetopolaron in a quantum dot has been extensively studied. Petukhov et al. studied the hopping and giant magnetoresisrance of a bound magnetic polaron in magnetic (semiconductors) and nanostrucrure with the golden rule at effective mass approximation. Charrour et al. presented a systematic study of the ground state binding energy of a hydrogenic impurity in cylindrical quantum dot subjected to an external strong magnetic field and performed calculations within the effective-mass approxi-(mation) using the variational procedure and considering an infinite confining potential on all surfaces of the (system.) Liu et al. investigated the properties of bound magnetopolaron in a quantum wires. Bouhassoune (et al.) studied magnetic field effect on the binding energy of a bound polaron in a quantum well by a variational method. Nguyen et al. analysized magnetic field effects of parabolic confining potentials and magnetic field on the binding energy of hydrogen impurites in quantum dots using a very simple trial function with only one (variational) parameter. Chen et al. derived ground state properties of the bound magnetopolaron using the linear combination operator and unitary transformation method. Corella et al. calculated the ground state and binding energy for the hydrogen impurity in a spherical quantum dot by using the variational method. Zhou et al. (derived) energy levels of the bound magnetopolaron by the variational method. Li et al. investigated the in-(fluence) of magnetic field on the binding energy of a hydrogenic impurity in cubic quantum dots, and so on. (However,) few investigators studied the average number of optical phonons around the electron in the quantum dot with the linear combination operator and a perturbation method so far. By using the linear combination operator and unitary transformation method, properties of the vibration frequency and the average number of optical phonons around the electron in the quantum dot are studied for the strong electron-LO-phonon coupling case. Results show that the vibration frequency decreases when the Coulomb potential enhances. While the vibration frequency and the average number of (optical) phonons decrease with the effective confinement length increasing and they increase with the electron-(LO- )phonon coupling strength.关键词：parabolic quantum dot;strong coupling;bound polaron;average number of optical phonons97|62|2更新时间：2020-08-11
- 摘要：The motion behaviours of the channelling particles have been controlled by an interaction potential of a particle with a crystal.Assuming to the interaction potential is the sine-squared potential, then the channelling effects and the channeling radiation are described analytically.In a harmoric approximation only one line is discovered in the channelling radiation spectra.The width of spectrum line is effected by Doppler effect, thermal vibration of lattice,electron multi-scattering and double-pole effect, besides the non-linearity of the system.Thus width of the spectra line has expanded almost.However, these factors may be decreased to minimum by effort, but the intrinsical extended width of the spectrum line by the radiation is not overcomed.Va-(rious) interaction potentials were compared, sine-squared potential is introduced to describte the interaction of the particle with the crystal.In a harmoric approximation of the sine-squared potential one disscused the intrinsical width and the frequency shift of the spectrum line for channelling radiations. Of course, the intrinsical width and the frequency shift of the spectrum line are very small in a classical approximation, However, this effect is obvious in a quantum mechanic frame, the shift magnitude is almost the same to the line width, this is so-called Lamb shift discovered by Soviet Physicist Lamb.In addition, in this paper the motion equation is derived in a classical mechanic frame, the solution of the equation is found by using pertubation method.The channelling radiation energy is calculated by a classical electro-dynamics.As example, the radiation energy for 1st order harmonic is for a positron with energy 56.0 MeV.It shows that the intrinsical width and the (frequency) shift of the spectra line are very small in all truth.关键词：sine-squared potential;channelling radiation;nonlinearity;spectral line96|72|3更新时间：2020-08-11
- 摘要：With the development of the growth techniques of the semiconductor, the well performanced heterostructures, quantum well and superlattice have been prepared,which is the great breach in Semiconductor physics and material science.The problem of confined electron in a quantum well(QW) has attracted much interest from physicists in recent years. Zhao et al. calculated the ground state, the first excited state and the transition energy of the electron(or hole) in the GaAs/Al0.3Ga0.7As parabolic quantum well by using a mo-(dified) Lee-Low-Pines variational method. Chen et al. investigated polaronic effects in a quantum well by using the Landau-Perkar theory. Comas et al. and Rücker et al. calculated self-energy of polaron and mageneto-(polaron) in a quantum well by use of the standard perturbation-theory. Chou et al. studied the ground state binding energy of hydrogenic impurity in a quantum well by using a general perturbative method proposed by Lee and Mei. Shen et al. discussed the binding energies of the hydrogenic donor ground state in a GaAs-Ga1-x-AlxAs quantum well of finite barrier height in presence of a magnetic field, which is taken to be parallel to the growth axis of the quantum-well structure by using strong-perturbation theory and pertubative-variational approach. Ren et al. calculated the ground-state energy of a polaron in parabolic quantum well in the presence of a Coulomb potential by using Feynman-Haken path integral theory.Eerdunchaolu et al. studied the tempe-(rature) dependence of the properties of electron-bulk LO phonon interaction system in a quantum well within (the electric-magnetic) fields along the growth axis by using variational wave-function and harmonic oscillator (operator) algebra method.The properties of the polaron in a quantum well are seldom investigated by using a linear-combination-(operator) method. In this paper, the properties of ground state of the polaron in an finite quantum well were investigated. The vibration frequency, ground state energy and ground state binding energy of the strong-coupling polaron in an infinite quantum well, the effects of well width L and electron-LO phonon coupling strength α on the vibration frequency λ,ground state energy E0 and ground state binding energy Eb of the strong-coupling polaron were discussed by using a linear-combination-operator and variational method. Numerical calculation (illustrates) that the vibration frequency and ground state binding energy of strong-coupling polaron in an infinite quantum well will decrease with increasing well width L and increase with increasing the coupling strength α;the ground state energy will decrease with increasing L and its absolute value will increase with increasing coupling strength α; our results approach those of 2D and 3D polarons respectively in the limits of small and large well width L.关键词：linear-combination-operator;strong-coupling polaron;infinite quantum well113|63|1更新时间：2020-08-11
- 摘要：Conjugated polymers as light emitting materials have attracted considerable attention during the past several decades. There is substantial ongoing research towards the design of blue light emitting materials for OLEDs based on conjugated polymers. The conjugation length, steric hindrance within the polymer, must be controlled for such purpose. It is well known that the binaphthyl unit possesses a large dihedral angle ranging from 60° to 120°. Therefore, the conjugation of the binaphthyl-containing polymers can be interrupted by the highly twisted binaphthyl unit. In addition, the highly twisted structure will reduce the intermolecular interaction of the polymers. As a result, the binaphthyl-containing polymers will have high quantum efficiency and good solubility. Binaphthalene chromophores were introduced into the backbone of conjugated copolymers with different aromatic groups by Wittig or Wittig-Horner reaction, three linear copolymers and a hyperbranched (copolymer) containing binaphthyl unites were synthesized. All the copolymers were characterized by FT-IR, (1H NMR.) They were readily dissolved in the common solvents such as tetrahydrofuran(THF), dichloromethane, and chloroform. Their photophysical properties have been studied. The results indicated that all copolymers show pure blue light emitting. It is mentionable that the hyperbranched copolymer BN-TPPV shows the highest quantum efficiency (95%) among the four copolymers, which exhibits two emission band peaked at 393 nm and 410 nm in chloroform and one broad emission band peaked at 428 nm in solid film. Cyclic voltammetry was employed to investigated the electrochemical properties of the polymers, their band gaps were ranging from 2.76 eV to 3.05 eV, this result testified that the polymers, BN-PPV, BN-PBPV, BN-TPPV, have the potential to be applied as blue light emitting materials. The results show that it is a practical way to prepare blue light emitting polymers by incorporating binaphthyl into polymer chain.关键词：binaphthalene;Wittig reaction;hyper-branched copolymer98|161|2更新时间：2020-08-11
- 摘要：Many aromatic carboxylate coordination compounds of rare earth have eximious photics, magnetics and catalysis properties in virtue of the structural multiformity. The 4f-3d hetero-metallic coordination polymers with particular structure mostly exist in dimer or multimer, and have latent application foreground at magnetism and luminescence materials. This paper aims to select α-furancarboxylic acid (HFur) and α-thiophenecar-(boxylic) acid (Htpca) with biggish conjugation system as ligands, 1,10-phenanthroline (phen) as cooperative (ligand,) Zn2+ ion as sensibilizer of Tb3+ ion luminescence, to synthesize 4f-3d hetero-metallic coordination (polymers) in the nature of excellent luminescent performance and good dissolubility, to investigate the influence of crystal structure and coordination field on the spectrum character. The 1-dimension coordination polymers Tb(Fur)3(H2O)2·DMF and Tb2Zn(Fur)8(H2O)2, and tetranuclear heterometallic complex Tb2Zn2-((tpca)10)(phen)2 were prepared by the rheological phase reaction method. These complexes have good dissolubi(lity in water) and/or organic solvents, and emit very strong green luminescence under ultraviolet excitation. The crystal structures were characterized with single crystal and powder X-ray diffraction. The ultraviolet(visible) absorption and fluorescence spectra were measured. In these polymers the metallic atoms are linked by means of carboxylate groups (-CO2-) with bidentate bridging and tridentate chelating-bridging, and the chain structures …Tb…Tb…, …Zn…Tb…Tb…Zn…Tb…Tb… and Zn…Tb…Tb…Zn were formed, respectively. The Tb3+ ions are in 8-coordination, 9-coordination and 7-coordination configuration, respectively. The average bond length of Tb-O are 0.239 5(4), 0.247 4(5) and 0.231 8(4) nm. It was revealed that Tb3+ ion in the coordination polymers with 1-dimension chain structure could generate very strong direct (excited) emission; when Zn2+ ion was inserted in …Tb…Tb… chain, the energy transfer between Tb3+ ions was weakened but the energy transfer from ligand to rare earth ion was enhanced. In the coordination compound without bridging (or bridge-chain) structure between Tb3+ ions, the direct excited emission of Tb3+ ion can not occur. In addition, in the low symmetric and strong coordination field of 7-coordinate geometry, 7FJ energy level of Tb3+ arose greater split, but in the case of 8-and 9-coordination it not split or small split.关键词：terbium;coordination polymer;luminescence;crystal structure;rheological phase reaction111|104|2更新时间：2020-08-11
- 摘要：During the last decade, conjugated polymers have attracted much attention because of their important applications in polymeric light-emitting diodes, photovoltaic cells, and field-effect transistors. Siloles are conjugated organometallic molecules that possess low-lying LUMO associated with the σ*-π* conjugation (arising) from the interaction between the σ* orbital of two exocyclic σ-bonds on the ring silicon and the π* (orbital) of butadiene moiety. As a result, siloles exhibit high electron acceptability and fast electron mobility. So far siloles have been utilized as efficient electron-transport materials and light-emitting materials in the construction of electroluminescence devices, and increasing interests have been paid to silole-base polymers. Benzothiadiazole and its derivatives are excellently narrow band-gap comonomers for modifications of known conjugated polymers, which can tune emission color of copolymers with enhanced emissive efficiency due to (efficiently) intramolecular and intermolecular energy transfer. Up to now, to the best of our knowledge, there is no report of a copolymer derived from a silole and benzothiadiazole or its derivative, and applications of a silole-based polymer in photovoltaic cells have not been investigated. Two novel alternating copolymers PS-BT and PS-DBT derived from 1,1-diethynyl-2,3,4,5-tetraphenylsilole and 2,1,3-benzothiadiazole (BT) or 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole (DBT) were prepared by palladium-catalyzed coupling reactions. UV-Vis absorption, photoluminescence (PL) and photovoltaic behaviour of the copolymers were also investigated. PS-DBT showed wider and stronger absorption in the visible light region, compared with PS-BT. Along with the increasing of solution concentration, red-shifting of the peak positions of PL spectra were found for the two copolymers. Photovoltaic cells were fabricated with a configuration of ITO/PEDOT/copolymers:PCBM(1:4)/Ba/Al. The open-circuit voltages for PS-BT and PS-DBT were 0.50 and 0.40 V, respectively. The fill factors for PS-BT and PS-DBT were 24% and 33%, respec-(tively). Under the illumination of an AM1.5 solar light simulator, the energy conversion efficiencies for PS-BT and PS-DBT were 0.009% and 0.032%, respectively.关键词：Silole;benzothiadiazole;alternating copolymer;photoluminescence;photovoltaic cell107|81|0更新时间：2020-08-11
- 摘要：Poly(aryleneethynylene)s(PAEs) can be used in polymer light-emitting devices (PLED) and photovoltaic cells due to their relatively high efficient energy transfer and luminescence. The emission color of PAEs can be turned by incorporating narrow band-gap comonomers into the PAEs' backbone. A new class of poly(aryleneethynylene)s containing an aryl heterocyclic structure was prepared by Pd-catalyzed cross couplings between 4,7-dibromo-2,1,3-benzothiadiazole(BT)and 2,7-diet-hynylene-9,9-dioctylfluorene(PFE)with different feed radio of PFE to BT, using Pd(PPh3)4 and CuI as catalysts in the presence of triethylamine and toluene. In the case of Pd-catalyzed cross couplings, each individual narrow-band-gap unit is separated from both sides by wide-band-gap segments when the narrow-band-gap component is under or equal to 50% in the copolymer. The narrow-band-gap units function as exciton traps allow efficient intramolecular energy transfer from wide-band-gap segments to narrow-band-gap unit. All these polymers had a number-average (molecular) mass, Mn, about 4 00012 000 and showed good solubility in chloroform and toluene. The actual molar ratios of PFE to BT in the copolymers were estimated by means of elemental analysis. The results indicate that the actual ratio of PEF to BT in the copolymer is very close to the feed ratio. The absorption and photoluminescent spectra of the copolymers were studied. The maximal emissions of PL and UV spectra slightly red-shifted with gradual increase of BT's content. The result indicates that when the polymer contains alternating narrow band-gap aromatic units BT and large band-gap units PFE the tendency is to form a π-stacked structure which will be enhanced due to intermolecular charge transfer (CT) between polymer molecules. So that we could tune the emission color of polymers through attaching different ratio of narrow band-gap comonomer.103|103|0更新时间：2020-08-11
- 摘要：Polymer light-emitting diodes (PLEDs) offer potential advantages for application in displays and lightings over other competing technologies due to their cheap and easy solution-based fabrication processing, e.g., spin coating, screen printing or inkjet printing, which allows for the possibility of low-cost and large-(area) mass production. Among polymer based systems, the fluorescent/phosphorescent dye doped polymer systems have the unique advantage of simplicity and flexibility. One of methods to achieve highly efficient, full color information display is polymers doped with highly efficient fluorescent dyes, which requires a energy match but also an efficient energy transfer between polymer (host) and dye (guest). DCM is a highly fluorescent orange-red laser dye and widely used in PLEDs as guest, and poly-vinylcarbazole (PVK) is generally used as a host material for PLEDs due to its high energy singlet or/and triplet excited states for fluorescent or/and phosphorescent dopants, favorable film-forming properties, durability, and hole mobility. Highly efficient PLEDs with DCM doped into PVK, as a light-emitting layer, have been demonstrated due to singlet formed in the host material (PVK) which can efficiently transfer energy to the guest (DCM) via Frster/singlet transfer processes. Recently, more attention has also been paid on the detail mechanism, e.g. energy transfer and charge trapping processes in PLEDs. Photoluminescence and energy transfer in DCM doped PVK thin films were investigated by steady-state and time-resolved ultra-fast photoluminescence. We observed that the DCM emission intensity increased and the PVK fluorescent lifetime reduced with increasing DCM doping concentration due to efficient Frster/singlet energy transfer from PVK to DCM, which is strongly correlated with a large spectral (overlap) between DCM absorption and PVK emission. The observed results were comparable with the (calculations) based on Frster energy transfer theory and the fluorescent decay data were estimated according to exponential function.关键词：DCM;PVK;fluorescent spectra;time-resolved ultra-fast spectroscopy;energy (transfer)104|65|0更新时间：2020-08-11
- 摘要：The electronic and optical performances of P-PPV light-emitting diodes with lithium fluoride insulating layer between the metal cathode and active polymer are studied. As for the polymer light-emitting diodes, optimization of charge injection lies in the dominant factors for substantive improvement performance. Since the minority carriers dominate the recombination thus the radiation, their injection takes priority over that of (majority) carriers. Generally in semiconducting polymers, holes are majority carriers while electrons are the (minority,) the carrier misbalance between electrons and holes further deteriorate in the fact that holes usually take possession of higher mobility and smaller injection barrier. To balance injection charge carriers and facilitate the (electron) injection, there are two commonly stratagems to be used in cathode fabrication. One is to employ low work function metals such as barium and calcium as cathode though they are susceptible to degradation upon water vapor and oxygen. The other choice is proposed to insert an insulating thin layer of lithium fluoride (between) polymer/electrode interfaces to build a bilayer cathode. As shown by the experiment results, the LiF/Al double-layer-cathode with Ba(Ca)/Al electrode devices can improve in luminescence performance. Band bending and injection potential decrease of minority carrier caused by the inlay of metal fluoride insulating (layer,) which is proposed to be responsible for the enhanced electron injection and improved performance in polymer light (emitting ) diodes.关键词：polymer light-emitting diodes;P-PPV;LiF;metal-semiconductor interface114|56|1更新时间：2020-08-11
- 摘要：The nanosized Sm-MCM (1:10) mesoporous molecular sieve was synthesized by means of sol-gel-assisted self-assembly at the interface of nonaqueous and aqueous phase with hydrolyzation reaction routine under basic conditions at room temperature. The HRTEM image shows that the samples have uniform particles with a dia-(meter) of 10~15 nm. The BET surface area, porosity and pore-size of Sm-MCM (1:10) are 621 m2·g-1,)1.25cm3·g-1, and 8 nm. That results of 29Si-MAS NMR show that q0, q1, q2, q3, Q2, Q3, Q4 ([(SiO)4-nSi)-(O-Sm- )n (n = 4,3,2 ,1), (SiO)4-mSi-(OH)m (m= 2,1,0)] at -44, -58, -67, -76,( -89,) (-107), -110 ppm, respectively, proves that the ion of Sm3+ has incorporated the framework of Si-O. The FTIR results show that the peaks near 970 cm-1 are assigned to the deformation vibration of silanol group. The as-product is calcined at 800℃ and the mesoporous material possess enormous specific areas and large porosity, it shows that the mesoporous material is ultrastable. The emission spectra of Sm-MCM, vesting in the transitions 4L17/2→6Hn/2 (n=11,13,15) of Sm3+ ion, show that samarium ion exists in special chemical (environment) of Sm-MCM.关键词：Sm-MCM;nanosized mesoporous molecular sieve;29Si-MAS NMR;HRTEM;luminescence114|91|2更新时间：2020-08-11
- 摘要：Red phosphor Ca4(La1-x-yGdxYy)1-nO(BO3)3:nEu3+ (LnCOB:Eu, Ln= La1-x-yGdxYy) was (synthesized) with the method of solid-state reaction at high temperature. The luminescent properties were investigated from vacuum ultraviolet (VUV, E>50000 cm-1, λ<200 nm) to visible region. The component with best luminescence intensity was found out and compare with commercial red phosphor. This system shows effective red emission under the excitation of low-pressure mercury lamp. The emission spectra of LnCOB:Eu3+ show the characteristic 5D0→7FJ(J=0, 1, 2, 3, 4) transition of Eu3+ ions under the excitation of 254 nm. Monitored the strongest 5D0→7F2 emission line (610 nm), they all have a broad and strong excitation band which centered at about 246 nm which is ascribed to the charge transfer band (CTB) of Eu3+-O2- and result in that the phosphor can be excitated efficiently by low-pressure mercury lamp. In the VUV range, there is a broad host absorption band located around 184~188 nm in the range from 150~200 nm, which include the (f-d) transition of Eu3+. And for Ca4GdO(BO3)3:Eu3+, this broad band is very stronger than that in another two hosts, which should be due to the existence of Gd3+ ions and the excitation efficiency can be enhanced (around) 184~188 nm effectively.关键词：Ca4(La1-x-yGdxYy)1-nO(BO3)3：nEu3+;red phosphor;VUV;composition optimization106|41|1更新时间：2020-08-11
- 摘要：The relationship between the structure of the host glass and the properties of the doped ions is useful for the design of glasses for the different applications. Well defined and sharp emission lines of rare earth ions may serve as structural probes for the environment of the dopant. The ultraviolet transparency of insulating glasses depends on the glass formers for the silicate, borate and phosphate conventional glasses. So this work studies how it does in calcium aluminosilicate glasses when MgO or La2O3 were added. It reports the absorption edge shifts and the changes of the optical band gaps were observed for Er3+ doped CAS glasses by adding MgO and La2O3 in them. Glasses with the batch composition (a) 9SiO2·26Al2O3·65CaO·1.0Er2O3·(0.3Yb)2O3, (b) 9SiO2·26Al2O3·58CaO·7MgO·1.0Er2O3·0.3Yb2O3 and (c) 9SiO2·26Al2O3·58CaO·7MgO·1.0Er2O3·0.3Yb2O3·5La2O3 were melted at around 1500℃ and annealed at temperatures near glass transition temperature for 4 h. Then the glass was cut and polished for spectroscopic measurements. The (refractive) index, the density and the absorption spectra were measured. The ionic packing ratio and the (Judd-Ofelt) intensity parameters are calculated. The absorption edge gives a measure of energy gap. The fact that the fundamental optical absorption edge for samples shifts towards shorter wavelengths with adding of MgO and La2O3 contents signifies the role of MgO and La2O3 in CAS glasses. Ω2, Ω6, and Eopt increase with the adding of MgO and La2O3. The Urbach energy obtained are consistent with the trend of Eopt values.关键词：calcium aluminosilicate glasses;erbium;optical band gap;Urbach energy123|68|1更新时间：2020-08-11
- 摘要：The plasma display panel (PDP) was regarded as the most promising medium for the wall hanging high definition television (HDTV) because the large sized PDP could be made relatively easily. Moreover, it offers a fast response, a wide viewing angle, a lower energy consumption and other advantages. In PDPs, three primary color phosphors are excited by the vacuum ultraviolet radiation from inert gas plasma, which imposed a unique requirement on the phosphors. Green emitting phosphors was very important for plasma display panel because human eyes were sensitive to green color. ZnSiO4:Mn2+ which was used in plasma display (panel) as a green emitter has a long decay time, has a decay time longer than 10 ms. Long decay time was not beneficial to (display.) Searching for new emitting phosphors with short decay time excited by VUV photon was a urgent thing. (Y,Gd)BO3:Tb powders were prepared by the conventional solid reaction method. The (structure) of the powders was checked by XRD. The emission spectrum of (Y,Gd)BO3:Tb excited by 147 nm dominated by 544 nm emission ascribed to 5D4→7F5 transition of Tb3+ ions. VUV and UV excitation spectra of (Y,Gd)BO3:Tb were investigated. It was found that the host absorption was located at about 150 nm. The band centered at 150 nm of (Y,Gd)BO3:Tb is stronger than that of YBO3:Tb which indicated that Gd3+ (enhanced) the host absorption. New peaks were present at about 276 nm in the excitation spectrum of (Y,Gd)-BO3:Tb and were assigned to the 8S7/2→6IJ transitions of the Gd3+,this result indicates that there is an energy transfer between Gd3+ ions and Tb3+ ions. The fluorescence decay curve of (Y,Gd)BO3:Tb indicated that the lifetime of green luminescence (at 10% intensity) of (Y,Gd)BO3:Tb is about 8 ms. The afterglow time of (Y,Gd)BO3:Tb can meet the demand for display application.关键词：rare earth;(Y;G d)BO3：Tb;VUV excitation spectra;decay time105|117|4更新时间：2020-08-11
- 摘要：The green and blue long-lasting luminescent glass has been successfully prepared, but the red long-lasting luminescent glass has not been reported at the present time. CaTiO3:Pr3+red long-lasting luminescent glass was obtained by two steps method. At the first, CaTiO3:Pr3+ long lasting luminescence powder and low melting glass powder were synthesized by high-temperature solid-state reaction respectively. Secondly, the two components were weighed in appropriate mass ratio and mixed homogeneously. Finally, the mixtures obtained were sintered at different temperature for 10 min. The afterglow properties were researched systemically. The effects of the amount of CaTiO3:Pr3+ in mixtures and the procedure conditions were studied also.The emission spectra of samples were measured. The emission peaks at 611.7 nm and 614.5 nm, corresponding to the transition 4f-4f(1D2→3H4)of Pr3+ ions, come from the CaTiO3:Pr3+ red long (afterglow) emission. There was a broad band from 350 nm to 550 nm in the excitation spectrum, which showed that the glass could absorb the energy from near ultraviolet to yellow green, so the samples could be excited by sun light and lamplight then emitte the red long lasting afterglow. When the mass proportion of glass powder and phosphors is within 95:5～80:20, the pure glass phase could be gained and excellent red long afterglow could be observed. The effects of the atmosphere and the fuse temperature on the luminescent property were studied. The samples prepared at 800℃ in air have better (luminescent) characteristic.关键词：long afterglow;CaTiO3：Pr3+;luminescent glass;rare earth142|91|1更新时间：2020-08-11
- 摘要：The effect of preparation conditions such as sintering temperature on the luminescence properties of SrTiO3:Pr3+ phosphors doped by compensation ions with various valences were studied to obtain best luminescence property. The doping ions with various valences were selected to verify the charge compensation effect on the luminescence intensity as K and Al seem to have similar charge compensation effect. PL spectra were measured to analyze the effect of preparation parameters, such as doping ions of K, Ca, Al and sintering (temperature,) on the luminescence properties of SrTiO3:Pr3+ phosphors. And XRD measurements were carried out to verify the crystal structure of prepared SrTiO3:Pr3+ phosphors. The results revealed that all samples emit red light at 610 nm originating from 1D2→3H4 transition of Pr3+ (ions.) The luminescence intensity varies with sintering temperature, while the samples sintered at 1 150℃ have the best luminescence intensity. Among K, Ca and Al doped samples, only the Al-doped samples have the (obvious) enhanced luminescence intensity, the strongest luminescence intensity was about 10 times as that of pure SrTiO3:Pr3+ phosphor without compensation doping. On the other hand, phosphor doped with K ions, which likely has similar charge compensation effect as that doped with Al ions, has little effect on the improvement of luminescence intensity. Contrary, it has similar intensity as that of either pure SrTiO3:Pr3+ phosphors or Ca-doped phosphors which are believed to have not such charge compensation effect. Above result about the effect of various ions doping on luminescence properties could be explained by combination of charge compensation effect and substitution structure effect. The charge compensation effect is effective only when the doping ions Al3+ is substitute for the Ti ions which is the nearest neighbor ion to the (luminescence) ions of Pr+Sr. Present study shows an optimal preparation condition and proposes a method to choose effective charge compensation ion for SrTiO3:Pr3+ phosphors with best luminescence intensity.关键词：charge compensation;luminescence;doping;sintering temperature;SrTiO3：Pr3+108|79|2更新时间：2020-08-11
- 摘要：Many experiments have reported that the siliconrich silicon nitride thin films can emit strong visible light at room temperature, at light excitation, and the silicon-rich silicon nitride thin films were usually prepared through plasma enhanced chemical vapor deposition (PECVD) technology or low pressure chemical (vapor) deposition (LPCVD) technology, among which the thin films made by PECVD technology was used and researched more often, for the lower temperature. Yet the silicon nitride thin films obtained by LPCVD have many advantages than the silicon nitride thin films by PECVD, including higher refractive index, higher den-(sity,) higher resistivity, higher breakdown field, higher band gap and so on. Moreover, although experiments concluded all the silicon nitride thin films showing photoluminescence have mosaic structure of silicon nano-dots embedded in amorphous silicon nitride films, the size and the number of silicon nano-dots is quite diffe-(rent) in the films made by LPCVD and PECVD, which means they may have different luminescence mechanics. So our team has researched the photoluminescence mechanics of silicon nitride films prepared by LPCVD in the last year. By choosing different deposition condition during the samples preparing, the microstructure and the defects of the thin films can be changed, as a result, the PL spectrum will change consequentially. Using TEM, IR and XPS, the luminescence mechanics of the silicon nitride thin films were investigated. We changed the ratio of dichlorosilane to ammonia, keeping the deposition temperature at 900℃. The result shows quite different PL spectra, and we has explained the results using our gap states (model.)关键词：nano-silicon microstructure;SiNx film;photoluminescence;low pressure chemical vapor depo-(sition) (LPCVD)114|71|2更新时间：2020-08-11
- 摘要：Many efforts have been made to seek structures grown on GaAs substrate with long emission wavelength for telecommunication, among which GaAsSb/GaInAs bilayer quantum wells embedded into GaAs layers provide a promising structure for realizing 1 300 nm emission. It has been pointed out that the GaAsSb/GaInAs conduction band alignment is of type-Ⅱ, with electrons confined in GaInAs layer whereas holes confined in GaAsSb layer.The relative strong ground state transition has been observed in photoluminescence (PL) spectra.However, the physical aspects of the bilayer quantum well (QW) structure were still not very well studied. For example, the experimental verification of band alignment between GaInAs and GaAsSb and the overlap integral of type-Ⅱ transitions were not well provided. The behavior of excited states transitions was reported, but had never been investigated by PL spectra, which is studied in this paper. The optical transitions in GaAsSb/GaInAs/GaAs bilayer quantum wells (QWs) are studied by photo-(luminescence) (PL) and photoreflectance (PR) measurements. Two PL peaks with large energy separation (>120 meV) are observed at 300 K, while at 10 K only the one at lower energy is observed. Further studies show that the PL peak with higher energy appears only at the temperatures above 150 K. The physical mechanisms of the two PL peaks have been identified to be different. The lower PL peak and the higher one belong to type-Ⅱ and type-Ⅰ-like transition, respectively. An optical transition model is formed and the wave functions overlap integrals of electrons and holes are calculated. The methods to enhance the lowest interband (optical) transitions of the QW are suggested based on the growth conditions of the studied samples.关键词：bilayer quantum wells;photoluminescence;GaAsSb/GaInAs100|93|0更新时间：2020-08-11
- 摘要：Recently, Pr-doped GaN has been attracting much interest because of its potential applications in optical communications and full color displays. Pr-doped GaN can produce IR emission at 1.3 μm and visible red emission at 650 nm. Pr ions are usually introduced into GaN either during growth process or by ion implantation. As we know that ion implantation doping has a lot of advantages, such as the selective doping of certain areas on the sample, the introduction of a large number of elements, and precise control of dopant concentration and depth distribution. It is necessary to anneal in order to achieve electrically or optically active doping and remove the damages induced by ion implantation. The micro-structure and photoluminescence (PL) properties of Pr-implanted GaN thin films have been studied. RBS/Channeling technique was used to explore the damage introduction of GaN:Pr sample and the damage recovery at high annealing temperature. A complete recovery of the ion implantation damage can not be achieved at annealing temperatures up to 1050℃. AFM results indicate that Pr ion implantation has caused surface roughness and pronounced material swelling with a step height as large as 23.368 nm. The PL experimental results indicate that the PL efficiency increases exponentially with annealing temperature up to the maximum temperature of 1050℃. The thermal activation energy Ea is 5.8 eV by data fitting.关键词：GaN;Pr;RBS/C technique;photoluminescence113|102|0更新时间：2020-08-11
- 摘要：Ⅲ-Ⅴ nitrides are promising direct transition semiconductor materials used for the application in both optoelectronic and electronic devices. Recently Si is viewed as one of the most promising substrates for the GaN epitaxy because of its high quality, large size, low cost and a well-known existing device technology. However, due to the large difference in lattice constant and thermal expansion coefficient, it is rather difficult to grow highquality single crystalline GaN on Si. Hexagonal GaN layers were grown on Si(111) substrates using high-temperature-grown AlN as buffer (layer) by a vertical MOCVD reactor. After the Si(111) substrate was annealed under H2 ambient at 1 100℃ for 10 min to clean the surface,a thin AlN buffer layer was deposited at 1 060℃ for 8 min,about 20 nm thick. After AlN growth, GaN with excessive Ga HT-GaN layer and with LT-GaN layer were grown at (1060℃), (about) 0.6 μm thick.The growth and characteristics of the GaN layers were investigated by using X-ray diffraction(DCXRD), scanning electron microscope(SEM), atomic force microscope(AFM) and room temperature photoluminescence spectrum(RT PL). These results indicate that the crystalline quality and morphology of GaN with excessive Ga HT-GaN layer is much better than that with LT-GaN layer. High-resolution X-ray diffraction exhibited a GaN(0002) and (101-2) spectra with full-width at half-maximum(FWHM) as low as 698 and 842 acrsec. A very strong band-edge emission peak at 361 nm(3.4 eV) is observed, with a FWHM of only 44.6 meV and no yellow (luminescence) exists.关键词：GaN;Si(111);MOCVD;DCXRD145|79|1更新时间：2020-08-11
- 摘要：ZnO is a Ⅱ-Ⅵ wide and direct band semiconductor. It has a large fundamental band gap of 3.37 (eV,)which makes it a promising material for use in ultraviolet light-emitting and laser diodes. Moreover, ZnO possesses a large exciton binding energy, which is much larger than that of GaN (25 meV) as well as the (thermal) excitation energy at room temperature (60 meV),and can ensure an efficient exciton emission at room temperature. The fabrication of one-dimensional ZnO nanostructures has also been of growing interest owing to the promising application in nanoscale optoelectronic devices. ZnO nanostructures can be fabricated by various methods such as pulse laser deposition, chemical or physical vapor deposition and thermal evaporation. However, to date, for practical (application,) low-temperature growth of well-aligned ZnO nanostructures arrays which have the well-faced hexagonal structure and controlled diameters will be required. In this work, various morphologies and different sizes of ZnO rods have been fabricated through a simple chemical solution on the glass substrates by altering pH, the concentration of solution and other factors. We analyzed in detail the in-(fluence) of the pH, concentration, catalyst and temperature on the morphology of the as-grown ZnO samples. XRD patterns of all samples indicated that ZnO is a wurtzite structure and no imputity phase was found. XRD pattern of regular hexagonal ZnO rods showed that ZnO rods mainly grew along the c-axis direction. And the photoluminescence spectrum showed that there was only a near UV emission with a peak at 368 nm, and the FWHM of the emission peak is only 45 nm.关键词：ZnO;nanorods;photoluminescence;chemical solution method128|172|1更新时间：2020-08-11
- 摘要：As one of potential photoelectric material, zinc oxide attracted a lot of attentions recently. Such as, its wide band gap (3.37 eV) and high excitonic binding energy of 60 meV make ZnO as a good candidate for developing short wavelength optical devices. Furthermore, the p-doping ZnO can be produced and the p-n structure of ZnO can be formed on the silicon substrate, both of characteristics make ZnO to be compatible with Si-based integrated circuits. Hence, ZnO film has wider application in opto-electronic industries.ZnO films can be easily prepared by reactive sputtering. techniques However, the surface state which caused by damages of bulk silicon surface and lattice mismatch impurity which contaminated in fabrication procedure can produce the level of surface state and deep level in heterojunction. Those levels affect the carries a lot.Generally the level formed by defects can reduce illuminant efficiency, producing non-radiation recombined, but deep level can also become efficient illuminant centre using wide band gap materials. So it is deserved to study deeply of the behavior of ZnO/p-Si heterojunction interface state. The high frequency C-V character can be used to measure the charge of space charge region varied with the voltage variation, this effect of capacitance can be described by differential capacitance. The C-V measurement supplied an important way to research the characteristics of heterojunction. With the help of the measuring C-V and I-V character, we can easily obtain the evidence that interface impurity state and defects in ZnO:Al/p-Si interface can have largely influence on electricity property of the heterojunction. We also found it was very useful to reduce the interface state (using) annealing procedure. It was clearly to see that the sample annealed in 800℃ had the larger illuminant efficiency.Whether annealed or not, the sample grown by RF sputtering technique can form an abrupt heterojunction, but the character of potential was not the same. As a large number of deep level and surface state level were in interfaces, the C-V curve of sample which was not annealed was aberrance and the I-V curve was exponential with reversing bias voltage. In condition of annealing under 800℃, we can observe the influence of interface state was eliminated, and improved rectifying characteristic of heterojunction.关键词：ZnO heterojunction;C-V characteristic;I-V characteristic;interface impurity states108|98|0更新时间：2020-08-11
- 摘要：Over the past few years, wide and direct band gap semiconductors have been intensively studied for their application as blue and ultraviolet light emitters. As a wide gap semiconductor, ZnO has a wide band gap of 3.37 eV and a large binding energy of 60 meV. Therefore, ZnO is considered as one of the most promising candidates for short wavelength optoelectronics devices, and it is very important to conduct further studies of the properties of ZnO thin films.An un-doped zinc oxide thin film was prepared by radio frequency (RF) reactive co-sputtering on silicon (100) substrate. Sputtering target was metal zinc (99.99%), the sputtering gas is a mixture gas of argon (99.97%) and oxygen (99.95%), the partial pressure ratio of oxygen is 0.4. The structure, surfaces (morphology) and PL spectra of the sample were characterized by X-ray diffractometer, atomic force microscopy(AFM) and fluorescent spectrophotometer, respectively. The X-ray diffraction patterns indicated that the film has highly c-axis orientation and low biaxial compressive stress (2.8×108 N/m2), the 2θ angle of (002) diffraction peak is 34.48° and the full width at half maximum is 0.306°. The grain size of the sample is about 50 nm. A strong blue emission peak and a weak violet emission peak located at 434 nm and at 414 nm are observed in the photoluminescence (PL) spectrum when exited with 325 nm wavelength (He-Cd) at room temperature. The full width at half maximum of blue emission peak is only 50 meV. We assigned that the violet (emission) and blue photoluminescence peaks originate from Zn vacancy and Zn interstitial defects, respectively.关键词：ZnO films;silicon substrate;photoluminescence;RF reactive sputtering114|80|2更新时间：2020-08-11
- 摘要：ZnO is a direct and wide-band gap semiconductor with WZ crystal structure. It has recently attracted considerable attention due to its favorable properties such as the wider band gap (3.37 eV) at room temperature, the large binding energy of excitons (60 meV) at room temperature, and highly c-axis oriented. ZnO has so good photoelectric and piezoelectric properties that it has immensity space for developing at surface (acoustic) wave devices, light emitting diodes (LEDs), photodetectors, gas sensor and solar cells etc. A variety of deposition techniques have been employed to prepare ZnO thin films, such as pulsed laser deposition (PLD), molecule beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). Among them, MOCVD provides the advantages of large-area deposition and high throughput due to higher growth rates. Consequently, MOCVD was adopted to grow ZnO thin films. High-quality ZnO thin films were grown on sapphire (0001) substrates at 590℃ for 20 min by metal-organic chemical vapor deposition (MOCVD). The effect of annealing under different condition on crystal structure and optical properties of ZnO thin films have been studied.The results show that the crystal quality of the films grown on c-plane has been improved largely. Especially the film annealed in oxygen, the XRD peak of ZnO (002) became stronger greatly and the FWHM of XRD peak is only 0.11°. The PL spectra show that the deep energy level emitting disappears in the sample annealed in nitrogen. On the contrary, the deep energy level emitting became stronger for the sample annealed in oxygen. The results show that the deep energy level emitting intensity is related to the concentration of VZn and OZn defects. Additionally, the resistivity of ZnO thin films annealed in oxygen could increase remarkably for the change of the rate of Zn and O. It was an effective method to achieve the high-quality ZnO films, high-resistance ZnO films, even p-type ZnO by annealing under proper condition from our results.关键词：sapphire;ZnO films;MOCVD;XRD;annealing123|83|0更新时间：2020-08-11
- 摘要：Microring resonator is a original integrated optics device, which has developed for several years. Being a basic elements, microring resonator coulpled to a waveguide vertically offers high-quality factors, in large scale photoelectric integrated circuits, it can be used as filters, multiplexers, modulators, lasers and etc. This component has promising application in wavelength-division multiplexing(WDM) system because of their (simple) structure, easier fabrication and compactness.Most of the microring resonator devices have been fabricated using semiconductor material. In this work, we use polymer to fabricate microring device, polymer has a number of advantages over semiconductor-based devices, the first one is to deduce loss, the use of low refractive index polymers will significantly reduce scattering loss, the second advantage is to provide better coupling efficiency to optical fibers than previously de-(monstrated) semiconductor waveguides due to the low index and the large cross section of the polymer waveguide. Polymer materials also have other properties such like the excellent photoelectric characteristics, lower cost and simpler fabrication. The structure and working principle of microring resonant wavelength multiplexers (MRRWM) and device design are discussed. In microring resonators, the coupling coefficient plays an important role in determining the device characteristics. The coupling coefficient depends exponentially on the gap distance between the ring and the straight waveguide. We analyzed the transmission characteristics, designed a 8 channels microring (resonant) wavelength multiplexer(MRRWM), the central wavelength of MRRWM is 1.55 μm, the wavelength spacing is 1.6 nm. To fabricate polymer waveguide in microring devices, the reactive ion etching (RIE) technique was used.The single channel and 8 channel polymer MRRWM with polymers based on silicon are fabricated. In the optical measurement, we used a tunable semiconductor laser with a tuning range from 1 530 nm to 1 610 nm, a digital optical power meter, and an optical spectrum analyzer were used to analyze the optical characters. A fiber-waveguide precision alignment system with infrared CCD camera was used for light coupling. In conclusion, polymer microring resonators were successfully fabricated by RIE technique, their optical (characters) were optimazed and analyzed.关键词：dense wavelength-division multiplexing(DWDM);microring resonator;multiplexer;polymer128|96|1更新时间：2020-08-11
- 摘要：A ZnO homo-junction light-emitting diode (LED) was fabricated on a-Al2O3 substrate by plasma-assistant molecular beam epitaxy. NO plasma activated by a radio frequency atomic source was used to grow the p-type ZnO layer of the LED. The current-voltage measurements at low temperatures showed a typical (diode) characteristic with a threshold voltage about 4.0 V at forward bias. Electroluminescence band of the ZnO LED is located at the blue-violet region at 80 K, and the electroluminescence still can be observed up to 200 K.关键词：ZnO thin film;p-type doping;p-n homojunction;molecular beam epitaxy156|93|0更新时间：2020-08-11
- 摘要：Core-shell structure ZnS:Tb/CdS nanocrystals(NCs) with sizes of about 4 nm were synthesized via reverse microemulsion technique. The structures, shapes and characteristic optical properties of ZnS:Tb/CdS NCs were characterized by means of X-ray powder diffraction(XRD), transmission electron microscopy(TEM) and F-4500 Fluorescence spectrometer. The XRD pattern of ZnS:Tb/CdS NCs was shown that the crystals (exhibit) zinc-blend crystal structure. The three diffraction peaks are corresponding to (111), (220), and (311) planes of the cubic crystalline ZnS, respectively. Due to the size effect, the XRD peaks were broadened and their widths become larger as the crystals become smaller. From the XRD analysis, no characteristic peaks of impurity phases were observed. The average sizes of ZnS:Tb/CdS NCs were calculated from the Debye-Scherrer equation to be around 3 nm. From typical TEM image, it is noticed that the average size of the ZnS:Tb/CdS NCs is about 4 nm. So the thickness of CdS shell is evaluated to be about 0.5 nm. The PL spectra of ZnS:Tb/CdS excited by 379 nm are composed of three peaks located at 489, 543, and 583 nm, which is assigned respectively to 5D4→7F6, 5D4→7F5, and 5D4→7F4 electron transitions of Tb3+ ions. An electroluminescent (EL) device having a hybrid organic/inorganic multilayer structure of ITO/ poly(3,4-ethylene dioxythiophene):poly (styrene sulfonate)(PEDOTPSS)(70 nm)/poly(vinylcobarzale)(PVK)(100 nm)/ZnS:Tb/CdS NCs (120 nm)/2,9-dimethyl -4,7-diphenyl-1,10-phenanthroline (BCP)(30 nm)/LiF (1.0 nm)/Al (100 nm) was fabricated. The two peaks located at 546 nm (5D4→7F5) and 577 nm (5D4→7F4) of the Tb3+ center were observed when the EL device was driven at applied bias of 13 V. It is also noticed that EL emission from PVK in the device was not observed, indicating that the electron-hole would be recombined in ZnS:Tb/CdS NC layer. The maximum luminance of 19 cd/m2 was obtained under the applied bias of 25 V.关键词：core-shell structure;ZnS：Tb/CdS;nanocrystal;electroluminescence;device129|59|0更新时间：2020-08-11
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