最新刊期
卷 27 ， 期 6 ， 2006
- 摘要：Taking into account the interaction of an electron with bulk longitudinal-optical (LO) and surface longitudinal-optical (SO) phonons, we study the ground state energy and self-trapping energy of the bound polaron in a polar slab by using the Huybrecht's linear combination operator method. The ground state energy and the self-trapping energy are all derived as function of slab thickness. Etre-ph includes two parts, one is Ee-LOtr, the other is Ee-SOtr, and Ee-SOtr also includes two parts, Ee-SOtr(+) and Ee-SOtr(-);taking KCl as an example, Ee-LOtr increases with the increase of the slab thickness, but Ee-SOtr,Ee-phtr and λ all reduce with the increase of the slab thickness, and when the slab thickness d is more than 5 nm, Ee-phtr is about to a stable number. Especially, vibration frequency (λ) increases when there is the Coulomb potential, because of the interactions are strengthened between the electrons and phonons.关键词：polar crystal slab;bound polaron;Huybrecht's linear combination operator;self-trapping energy103|107|2更新时间：2020-08-11
- 摘要：Some properties of the strong- and weak-coupling polaron in an asymmetry quantum dot are studied by the linear combination operator and unitary transformation methods. The ground state energy and the ground state binding energy of the polaron as a function of the transverse and longitudinal effective confinement length of the quantum dot and the electron-phonon coupling strength are obtained. It is shown that the ground state energy and the ground state binding energy of the strong- and weak-coupling polaron will increase strongly with the decreasing of the transverse and longitudinal effective confinement length of the quantum dot.关键词：asymmetry quantum dot;polaron;linear combination operator;effective confinement length104|90|7更新时间：2020-08-11
- 摘要：Negative materials(with negative refraction) are the oddity electromagnetism materials, very recently, Pendry proposed a revolutionary conceptof“perfect lens”: with the perfect lens, notonly the phase of propagating waves but also the amplitude of evanescentwaves from a near-field object could be restored at its image. The Fibonacci quasi2lattice have abundance content and simple structure.关键词：left-handedmaterial;Fibonacci supper-lattice;transfer-matrix;defects;transmission coefficient137|82|2更新时间：2020-08-11
- 摘要：Photonic crystals are artificially fabricated periodic dielectric structures. In recent years, a lot of theories and experiments on the application of photonic crystals have been studied. The two-dimensional photonic crystals have more advantage than one-dimensional photonic crystals and the three-dimensional ones, so the theory and application of two-dimensional photonic crystals are still one of the hottest themes in materials science and photonics science. There are various methods on studying transmission characteristics of photonic crystals: the plane wave expansion method(PWE), the finite-difference time-domain (FDTD), transfer matrix method (TMM), and multiple scattering method (Order-N). Shangshen Feng et al. used the plane-wave method for quickly calculating a band structure of two-dimensional photonic crystal with triangular lattice, but their studies didn't take into account the square cylinder rods photonic crystals, and the corresponding transmission spectrum was not obtained. In this paper, the transfer matrix method is used to study the transmission characteristics of two-dimension cylindrical photonic crystals of square dielectric rods with different lattice structures, section areas and azimuth angles. In numerical simulation the Mur absorbing boundary conditions and periodic boundary conditions are used to eliminate non-physical reflection of electromagnetic waves considered the actual structure. The numerical studies show that the photonic band gap width depends on the center frequency and lattice structure, the square lattice is easier to form smooth photonic band gap and the larger cylinder-sectional area is,the wider band gap is. In the same conditions as other factors, azimuth angle of cylinder impacts the photonic crystal band gap. The numerical study shows in the design of smooth photonic band gap of the square dielectric rod, the square lattice structure is considered first, then try to make the cylinder section as large as possible, finally, the photonic band gap width and center frequency can be fine-tuned to reach design requirements by changing the cylinder azimuth angles. In particular, no literature has reported the results that the band gap can be adjusted by the position azimuth angle, which expands the research of two-dimensional photonic crystals.关键词：2-D photonic crystals;the transfer matrix method;transmission characteristics;square dielectric rods108|191|0更新时间：2020-08-11
- 摘要：In the early 1980's, Tokuda investigated the mean number of phonons in the cloud around the electron for both the optical and the piezoelectric polarons within the scheme of variational approach based on the unitary transformation and the method of the Lagrange multiplier. Many investigators studied the properties of the mean number of phonons of polaron by many other methods. Recently, the properties of the mean number of phonons of the polaron and the bound magnetopolaron in a symmetric quantum dot have been studied using the linear-combination operator and unitary transformation method by one of the present authors and co-worker. However, using linear-combination operator method, the properties of the mean number of phonons for polaron in an asymmetric quantum dot has not been investigated so far. In this paper, the influences the asymmetric parabolic confined potential on the properties of the mean number of phonons for the polaron in quantum dot are studied by using linear-combination operator and the unitary transformation method. The relations between the mean number of phonons and the vibrational frequency of the strong- and weak-coupling polaron in an asymmetric quantum dot with the transverse and longitudinal direction confinement strength of the quantum dot and the electron-phonon coupling strength are derived. Numerical calculations on the RbCl crystal, as an example, are performed, and the results show that the mean number of phonons and the vibrational frequency of the strong-coupling polaron will increase strongly with increasing the transverse and longitudinal confinement strength of the quantum dot. The mean number of phonons and the vibrational frequency of the strong-coupling polaron will increase with increasing the electron-phonon coupling strength.关键词：asymmetric quantum dot;mean number of phonons;confinement strength;linear-combination operator108|109|2更新时间：2020-08-11
- 摘要：The ground state of the magnetopolaron, which is weakly coupled with the bulk longitudinal optical phonons and strongly coupled with the interface optical phonons, in an infinite quantum well within a magnetic fields are studied by using Tokuda' linear-combination operator and the modified Lee-Low-Pines variational method. The law of the change of the effective mass of the magnetopolaron changing with the quantum well's width and the magnetic fields are obtained. Numerical calculations, taking the AgCl/KI quantum well as an example, are performed. The results show that as the following: 1.The effective mass of the magnetopolaron in the quantum well is composed of two parts:the first part is the effective mass of the magnetopolaron induced by the interaction between the electron and the longitudinal optical phonon, the second part is the contribution of the interaction between the electron and the interface optical phonons and the magnetic fields. We have found that, among the four branches of the interface optical phonons, only the interaction between the electron and two branches of the interface optical phonons with frequency of ω++ and ω-+, the magnetic fields has the contribution to the effective mass of the magnetopolaron also, but other two branches of the interface optical phonons with frequency of ω+- and ω-- have not any contribution to the effective mass of the magnetopolaron. 2.The total effective mass of the magnetopolaron will decrease drasticlly with increasing the well's width, at last, it will tend to the limiting value of the bulk case slowly. This shows that, when the well's width is smaller, the contribution to the effective mass of the magnetopolaron by the interaction between the electron and the interface optical phonons is important, on the contrary, the contribution to the effective mass of the magnetopolaron by the interaction between the electron and the longitudinal optical phonon increases with increasing the well's width, and becomes the dominant. 3.The effective mass of the magnetopolaron will increases with increasing the magnetic field. It is indi- cated that the magnetic fields will intensify the interaction between the electron and phonons, and will influence on the interaction between the electron and the interface optical phonons only, but has nothing with the interaction between the electron and the longitudinal optical phonon.关键词：quantum well;strong-coupling magnetopolaron;effective mass125|123|0更新时间：2020-08-11
- 摘要：Since Tang and Van Slyke reported the first high efficiency organic light-emitting diodes (OLED) in1987, indium tin oxide (ITO) has been the most investigated OLED anode material due to its high transparency, high conductivity, and, particularly, high work function. The treatment of the ITO surface usually has a strong influence on the performance of the OLED device, suggesting that the interface between the ITO and the organic layer is quite important. Furthermore, the hole mobility in the hole-transporting layer (TPD) and electron mobility in the electron transporting layer (Alq3) are 1×10-3 and 5×10-5cm2·V-1·s-1, respectively, resulting in an imbalance in electron and hole concentrations in the emission layer. It is very necessary to improve the balance of holes and electrons injected to the emitter layer. One efficient method to improve the performance of OLED is to insert a buffer layer at the interface between the ITO anode layer and organic layer. We report OLEDs using ZnS ultra-thin film by RF magnetron sputtering as a hole injecting buffer layer with different thickness. The device with a typical structure of ITO/ZnS/TPD/Alq3/Al (TPD:N,N′-diphenyl-N,N′-bis (3-methylphenyl)-1,1′-biphenyl-4, 4′-diamine, Alq3 : tris(8-quinolinolato)-aluminum) performed a good electroluminescent properties compared with that without ZnS buffer layer. The investigation on the effects of the ZnS thickness showed that the diode with 5 nm ZnS buffer layer double its current density and luminance, and the current efficiency of the devices with 10 nm ZnS is improved by about a factor of eighteen percent compared with the devices without buffer layer. ZnS can be expected as a good buffer layer material due to its wide band gap, thus blocks part of the injected holes from the ITO anode to the organic layer (TPD) and improves the balance of hole and electron in jections in the devices.关键词：OLEDs;ZnS thin film;hole buffer layer;current efficiency109|116|1更新时间：2020-08-11
- 摘要：Anew rare earth complex TbGd(BA)6(bipy)2 was synthesized, which was used as an emitting material in OLEDs. By doping into poly N-vinylcarbazole(PVK), stability and conductivity of terbium complex are improved. As can be seen from photoluminescence spectra of the blended film, the emission peaks at 405, 489, 545, 585, 620 nm respond to PVK and 5D4→7FJ(J=6,5,4,3) transition of Tb3+ ions respectively. The photoluminescence of PVK, terbium complex and their co-system indicated that energy transferred from PVK to terbium complex is respected as both the ratio of their blend and the state of terbium complex dispersed into PVK. When the m(PVK):m(TbGd(BA)6(bipy)2) is 5:1, the energy transferred from PVKto terbium complex completely. In order to study electroluminescence mechanism of the terbium complex, two series devices were fabricated with structures:(1)ITO/PVK:TbGd(BA)6(bipy)2/Al;(2)ITO/PVK:TbGd-(BA)6(bipy)2/Alq3/LiF/Al. The emitting film was prepared by spin coating PVK:TbGd(BA)6(bipy)2 chloroform solution with mass ratio 5:1 onto the clean dry ITO glass. Then, the layers of Alq3, LiF and Al were deposited by vacuum deposition. For single-layer and double-layer devices, the emission of PVK is completely restrained, and only the green emission from Tb3+ is observed in electroluminescence, which is different from that in photoluminescence. The characteristics of these devices are investigated that not only energy transfer but also direct sequential charge trapping appeared to be the operating mechanism. In the charge trapping process, PVK is a hole transporting material and terbium complexes play a role as electron trapping centers. Terbium complexes trap electrons and holes, which enable direct recombination on terbium com- plexes. In the double-layer devices, holes and electrons were recombinated at the interface of emitting-layer/electron-transporting-layer. With increasing the thickness of Alq3, especially at highly electric field, exciton recombination region transferred closely to electron transporting layer. From the optimized double-layer device, bright and green emission from terbium complex had been obtained with the highest brightness of 183 cd/m2 at 13 V.关键词：terbium complex;emitting characteristics;energy transfer;rare earth complex107|127|1更新时间：2020-08-11
- 摘要：Aseries of phosphor samples of 2(Ba1-xSrxO)(1-y)P2O5·yB2O3:Eu2+ (0≤x≤1, 0<y<0.2) have been synthesized and studied. The excitation spectrum measurement showed that the absorption of the 2(BaO)·(1-y)P2O5·yB2O3:Eu2+ is located from 300 nm to 380 nm and the emission band locates at about 400~430 nm(0<x<0.16). The band of the host absorption (300~380 nm) moves about 40 nm to lower energy region and emission spectra shows a strongest emission peak at 478 nm as Sr2+ replaces Ba2+ partially(x>0.16) in the 2(Ba1-x-SrxO)(1-y)P2O5·yB2O3:Eu2+.关键词：rare earth;UV excitation;luminescence102|35|0更新时间：2020-08-11
- 摘要：Four kinds of Nd3+ doped PbWO4 single crystals with different doping concentrations were grown by a vertical Bridgman method and Czochralski method. The purpose of this research is to investigate the influence of Nd3+ doping concentration on the band gap structures and the luminescence properties on the base of optical absorption edge and luminescence of PbWO4 single crystals, respectively. The optical absorption spectra of PWO:Nd3+ crystals were measured at first. The dependence of absorption coefficient and the optical absorption edges on the doping levels of Nd3+ ion were investigated. Compared to that of pure PbWO4, the optical absorption edges in Nd3+ doped samples at lower concentration 0.15% show the shift to high energy region (short wavelength). With increasing of Nd3+ doping, the optical absorption edge greatly shifts to the low energy region (long wavelength). Based on the J-O theory, the phenomenological intensity parameters, intermanifold luminescence branching ratios, irradiative lifetime of the 4F3/2 level, the absorption and emission cross section of the PbWO4:Nd3+ crystals were calculated. Photoluminescence of PbWO4:Nd3+ crystals were discussed. In PbWO4:Nd3+, luminescence from PbWO4 host, especially the exciton excitation, are supressed with increasing of Nd3+ doping concentration; and in Nd3+ heavily doped PbWO4, new excitation bands related to the oxygen vacancy were created. Fluorescence intensity and lifetime of 4F3/2→4I11/2 excited by laser diode (LD) and its lifetime at room temperature show a dependence of Nd3+ concentration. Under excitation by 808 nm laser diode, PbWO4:Nd3+ 2.0% show an efficient 1.06 μm emission (950~1100 nm).关键词：lead tungstate single crystal;Nd3+ doping;luminescence spectra;effects of doping concentration;optical materials and properties128|112|2更新时间：2020-08-11
- 摘要：Before the nineties of the twentieth centuries the radioactive luminescence materials were used in the feeble illumination. At the beginning of the nineties of the twentieth centuries the aluminates long afterglow photoluminescence materials were invented. Soon afterwards they were used in the feeble illumination. At the nineties of the twentieth centuries the non-radioactive luminescence materials were needed in the military industries in China. CaAl2O4:Eu2+,Nd3+,La3+ is an important blue long afterglow photoluminescence material. The materials are not radioactive. The preparation and the photoluminescence properties of CaAl2O4:Eu2+,Nd3+,La3+ are investigated in the paper. CaAl2O4:Eu2+,Nd3+,La3+ was synthesized by solid-state reaction at high temperature at a reductive atmosphere. The reductive atmosphere was the mixture of N2 and H2. The reaction temperature was about 1320℃. Nd3+ and La3+ are the assistant activator. La3+ was added in CaAl2O4:Eu2+,Nd3+ for the first time. La3+ can prolong the visible afterglow time of CaAl2O4:Eu2+,Nd3+. We detected the excitation spectrum,the emission spectrum and the visible afterglow time of CaAl2O4:Eu2+, Nd3+,La3+. The emission spectrum of the CaAl2O4:Eu2+,Nd3+,La3+ sample tells that the maximal emission intensity is at λ=440 nm. The excitation spectrum of the CaAl2O4:Eu2+,Nd3+,La3+ sample tells that the 280～380 nm lights can excite the material. The visible afterglow time of CaAl2O4:Eu2+,Nd3+,La3+ is lasting more than 18 hours. The material will be used widely. Mechanism of the long afterglow photoluminescence is discussed. Electron traps play an important role in the long afterglow photoluminescence of CaAl2O4:Eu2+,Nd3+,La3+. Eu2+ is the luminescence ion. The photoluminescence of CaAl2O4:Eu2+,Nd3+,La3+ comes from the 4f65d→4f7 electron transition of Eu2+.关键词：CaAl2O4：Eu2+;Nd3+;La3+;long-afterglow;photoluminescence;trap106|132|0更新时间：2020-08-11
- 摘要：The 147Pm-excited ZnS:Cu,Cl luminescence powders are the important radioactive luminescence materials. They are used widely in the feeble illumination. Now they are investigated and produced only at Tsinghua University in China. The preparation and the luminescence properties of 147Pm-excited ZnS:Cu, Cl luminescent powders are investigated in this paper. The ZnSpowders with high pureness were used as the matrices. It is a direct bandgap semiconductor. Firstly the ZnSpowders were mixed with CuCl2 and the flux uniformly. Then the homogeneous mixtures were calcinated in the furnace for 1.5 hours at 1150℃ to make the ZnS:Cu,Cl powders. At the same time it changed to the hexagonal crystals. Finally the ZnS:Cu,Cl powders were coated with SiO2, Na2SiO3 and 147Pm2O3. So the 147Pm-excited ZnS:Cu,Cl luminescent powders were prepared. We detected the excitation spectrum and the emission spectrum of ZnS:Cu,Cl. The excitation spectrum of the ZnS:Cu,Cl tells that the maximal excitation intensity is at 341 nm. On the basis of that, we calculated the bangap energy of ZnS. It is about 3.64 eV. The emission spectrum of the ZnS:Cu, Cl tells that the maximal emission intensity is at 513 nm. The maximal brightness of the 147Pm-excited ZnS:Cu, Cl is 312 mcd/m2. The analyses tell that the luminescence lifetime of this phosphor is longer than5 years. The luminescence mechanism of the 147Pm-excited ZnS:Cu,Cl is discussed in this paper too. The stable luminescence of the 147Pm-excited ZnS:Cu,Cl is based on the quasi-equilibrium between the excitation and the recombination processes. The green luminescence of ZnS:Cu,Cl comes from the deep donors to the deep acceptors recombination emission. We calculated the energy level between the deep donors and the deep acceptors of ZnS:Cu, Cl according to the experiment results. It is about 2.42 eV.关键词：147Pm-excited;ZnS：Cu;Cl;luminescence;mechanism105|86|0更新时间：2020-08-11
- 摘要：Rare earth oxysulfide phosphor is a class of important luminescent materials. Because of their excellent properties, they have been applied extensively in fluorescent materials, X-ray phosphors, long afterglow phosphors, upconversion materials, and so on. So, rare earth oxysulfide phosphors are drawing more and more attention in recent years. Rare earth oxysulfide phosphors are usually produced by traditional solid-state reactions. In solid-state reactions, high reaction temperature, long heating time, and a special protective atmosphere are required to obtain a pure crystal phase. Therefore, producing agglomerated particles of irregular shape by solid-state reactions is unavoidable. Another disadvantage is the destruction of phosphor material during grounding and milling. The destruction results in the greatly decreasing of luminescence efficiency of the phosphors. In our present work, La2O2S:Eu, a red-emitting phosphor was rapidly synthesized by microwave radiation method for the first time. The synthesized phosphors were investigated respectively by XRD, SEM and fluorescence spectroscopy. The results show that La2O2S:Eu phosphors possess hexagonal crystal structure, which is similar to that of pure La2O2S. The particles of La2O2S:Eu phosphors are unregular in shape, dispersing well. The mean particle size is about 2 μm. The excitation spectrum of La2O2S:Eu is a wide band in the range of 200~450 nm. It results from the charge transfer states of Eu3+ ions (Eu3+-O2-, Eu3+-S2-). Anarrow peak at 472 nm can been found in the excitation spectrum attributed to the f-f transition absorption of Eu3+ ions. The emission spectrum shows that La2O2S:Eu has a series of narrow emission peaks located at 512,539,556,583,596,617 and 627 nm. These emission peaks are attributed to Eu3+ ions transition from 5DJ(J=0, 1, 2) to 7FJ(J=0, 1, 2, 3, 4). All the emission peaks are ascribed as follows, 617 nm and 627 nm (5D0→7F2), 596 nm (5D0→7F1), 583 nm (5D0→7F0), 556 nm(5D1→7F2),539,(5D2→7F4),512 nm (5D2→7F3). With the increase of Eu3+ mol fraction from 2% to 10%, the main excitation peak shows an obvious shift to the long wavelength from 348 nm to 365 nm; the emission peaks in blue and green region become weaken gradually relative to the main emission peak at 627 nm. Therefore the red emitting at 627 nm become stronger gradually. When the content of Eu is 8%, the red emitting becomes the strongest. Further increasing the molar ratio of Eu3+, the intensity of main emission peak will decrease.关键词：La2O2S：Eu;microwave method;excitation spectrum;emission spectrum110|90|4更新时间：2020-08-11
- 摘要：The photoluminescence of ZnOepitaxial film grown by MBEmethod was investigated. Some obvious interference fringes were observed in the reflection spectrum of ZnOfilm at room temperature due to Fabry-Perot interference, the Fabry-Perot interference indicates that optical quality of the sample is very good. Using the empirical equation of refractive index, the thickness of the film is estimated about 800 nm. The PL spectrum of the ZnOwas investigated under different excitation intensity using waveguide and backward configurations. In PL spectrum of waveguide configuration, six peaks at 383, 390, 392, 406, 438 and 502 nm were observed obviously. The peak at 392 nm appeared when excitation intensity is above certain values and then increased superlinearly. Wide spontaneous emission was observed in PL spectrum in backward configurations with low intensity. With the increasing of the excitation intensity, a new peak at 392 nm appeared. With further increasing of the excitation intensity, another new peak at 396 nm appeared, its intensity increases rapidly, its location shifts to red and width of the peak is broaden with the increasing of excitation intensity. It is thought that mechanism of the two peaks is identical, which is due to both defect scattering and exciton-exciton scattering. It was analyzed that there are the angle dependence of photoluminescence and striking difference in spontaneous spectrum between the two different configurations. The spectrum using waveguide configuration is more structured. Two effects may be responsible for the experiment results: one is the wavelength selection effect due to the absorption of guided-mode in asymmetric waveguide; the other is Fabry-Perot like interference of the grazing light in substrate (micro-cavity effect). The theory results of the two different explanations are thought to be equal in the film plane.关键词：ZnO;photoluminescence;Fabry-Perot interference;waveguide130|97|2更新时间：2020-08-11
- 摘要：ZnO has become a promising material for ultraviolet light emitting diodes and lasers, transparent high power electronic devices dut to their wide direct band gap and large exciton binding energy. Undoped ZnO exhibits intrinsic n-type conductivity, and it is, therefore, difficult to achieve p-type ZnO. Among group-V dopants, N is considered to be a shallow p-type impurity; however, there are stillmany difficulties forusingN as dopan.t Recently, much efforthas been devoted to fabricate p-type ZnO with codopants. So it is important to understand the codoping effecton electronic structures of wurtzite ZnO.关键词：ZnO;p-type doping;band structure111|185|1更新时间：2020-08-11
- 摘要：ZnO has awide band gap of 3.37 eV, low lasing power threshold for optical pumping at room temperature, and UV emission resulted from a large exciton binding energy of 60meV, so itcan be used as light emitting diodes (LED), photodetectors, and shortwave laser. To fabricate the devices, high quality ZnO thin films are often required, such as they should have good crystal properties with high c-axis orientation and low stress. Many researches have been done on the preparation of high quality ZnO films in recentyears.关键词：ZnO thin film;RFmagnetron sputtering;XRD;SEM122|119|0更新时间：2020-08-11
- 摘要：ZnO is a very useful and interesting ceramic material,since it exhibits a variety of properties such as semiconductive, photoconductive, piezoelectric and electro-optical behavior. Due to these characteristics, structure, properties and preparation methods of ZnO films have been extensively studied for practical applications. Different from other preparation methods, a series of ZnO films on glass substrate have been prepared by ion beam reactive sputtering with metal Zn (purity 99.99%) as target. X-ray diffraction (XRD) spectra analysis of the ZnO films indicates that the films are single (0002)-oriented growth although preparation condition changed. Temperature of substrate is a key factor on preferential orientation growth of ZnOfilm in (0002) direction. Ratio of Ar/O2 (sputtering gas) has a little affection on structure of the films. 360℃ is a most adaptive substrate temperature for ZnOfilms single (0002)-oriented growth, and high quality ZnOfilm with absolute c-axis orientation has been successfully achieved at this temperature. Photoluminescence (PL) spectra show that some PLpeaks are very strong at wave band of both ultraviolet (364 nm) and blue-green (470 nm) under excitation of 270 nm, another PLweak peaks appear at violet (398 nm), blue (452 nm) and infrared (722 nm) band. Among the peaks, PLpeak of 470 nm has not been reported up to now. Annealing in air has significant influence on structure, photoluminescence and electric properties of the films. An appropriate annealing temperature can promote single c-axis oriented growth of ZnO films, make crystal grains much bigger, luminescence intensifying and make resistance raising of the ZnO films. 400℃ is a optimum annealing temperature for single (0002)-oriented growth of the ZnO films and enhancing the film's luminescence intensity. Resistance of ZnO films increase with not only pressure of oxygen enlarging, but also substrate temperature raising. After 350℃ annealing in air, ZnO films become insulators. The results indicate the film's PL property has no relationship with its resistance.关键词：ZnO film;crystal structure;photoluminescence;electric property;ion beam sputtering102|133|0更新时间：2020-08-11
- 摘要：ZnO is a novel wide band gap semiconductor material for optoelectronic applications and has received extensively attention in recent years. The growth of high quality ZnO materials and p-type doping for ZnO films are key techniques for the development of ZnO based optoelectronic devices. Our previous study shows that ZnO films grown by ultrasonic spray pyrolysis (USP) can easily be doped to p-type, and the resulting p-type film exhibits low resistivity and high hole concentration. However, USP method is difficult to grow ZnO films with high quality crystal structure, which limits the application of ZnO films by USP. In this paper, we aim to improve the crystallinity of the USP-grown ZnO films by introducing a high quality ZnO seeding layer. We firstly deposited a ZnO seeding layer on Si(100) by pulsed laser deposition (PLD), and then grew ZnO film on the seeding layer by USP method. The ZnO seeding layer by PLD shows high quality crystal structure with highly (002) orientation and atomic scale smooth surface. The effect of ZnO seeding layer on the crystal quality and photoelectrical properties has been studied. Results indicate that by the induction of the seeding layer, ZnO film changes from multi-oriented polycrystalline structure to highly (002) oriented structure with significantly enhanced crystallinity. The resultant film possesses columnar microstructure perpendicular to the substrate and exhibits smooth, dense and uniform morphology. In order to characterize the photoelectric properties of ZnO films, we measured the photoelectric response of ZnO/Si heterojunction. It is concluded that ZnO/Si heterojunction formed by ZnO film with seeding layer exhibits markedly higher photocurrent at reverse bias and significant pen-circuit photovoltage at UVillumination, compared with the heterojunction by ZnO film without seeding layer. The present study provides a good starting point for preparation of p-type ZnO films with both excellent electrical properties and high quality crystal structure.关键词：ZnO film;seeding layer;spray pyrolysis;crystal quality;photoelectric property112|156|0更新时间：2020-08-11
- 摘要：The different preparation method has tremendous influence on the microstructure and the performance of ZnO-based thin films. The exploration of new method which made low cost and high quality sample seems to be very important now. Considering the practical application, searching a higher Curie temperature thin magnetic semiconductor material also has an important value. Using PVA method, the Co2+ and Fe3+ ions doped ZnO diluted magnetic semiconductor thin films were prepared. This method which has many advantages:such as simple operation, short sample preparation time, low cost, may conveniently be used to prepare big area semiconductor thin film. At the same time, PVAmethod can be used to prepare uniform and high purity sample, also has advantageous for the doping control. The structure of Zn0.88Co0.12O thin films under different annealing time and its photoluminescence were investigated. Different preparation conditions will influence on the microstructure, ferromagnetism and photoluminescence of samples obviously. Using PVA method we prepared the Zn0.88Co0.12O sample which has obviously (002) orientation. We also analyzed the origin of the ultraviolet peak and the blue light peak. Using vibrating sample magnetometer (VSM) we found that both Zn0.88Co0.12O and Zn0.88(Co0.5Fe0.5)0.12O thin films have ferromagnetism at room temperature, and the Zn0.88Co0.12O thin film has higher ferromagnetic intensity than that of the Zn0.88(Co0.5Fe0.5)0.12O thin film. Through the structure analysis and the computation, we confirmed that the magnetic ions entered into the ZnO crystal structure indeed.关键词：PVA method;zinc oxide;doping93|107|2更新时间：2020-08-11
- 摘要：The difficulty in the fabrication of p-type ZnOhinders the development of ZnO-based devices. Group-Ⅰand group-V elements substituting for Zn and Ocan respectively form the different acceptor dopants. Park C Hcalculated the energy levels of different acceptor dopants in ZnO, and it is found that group-Ⅰ elements substituting for Zn are of a shallower acceptor level than group-V elements substituting for O. Especially the acceptor level of Li substituting for Zn (LiZn) is 0.09 eV, which is the shallowest value among the energy levels of acceptor dopants in ZnO reported. However, when Li atom substitutes for Zn, it will easily be accompanied by the formation of interstitial Li (Lii), which is likely to be shallow donor. This causes the p-type doping to be limited by the formation of a LiZn-Lii complex donor. Based on above, Li was used as the acceptor dopant substituting for Zn in this work. In order to repress the formation of Lii, nitrogen was used as a codopant with lithium by a two step annealing process to form LiZn-N complex acceptor.关键词：ZnO;alloys;annealing;vacuum deposition;p-type94|83|2更新时间：2020-08-11
- 摘要：Recently, diluted magnetic semiconductors (DMSs) have attracted a lot of attention because of their potential technological applications in optoelectronic, magnetoelectronic, and microwave devices. Ⅱ-Ⅵ semiconductors such as ZnO are attractive as DMS candidates because the solubility limit of magnetic ions is extremely high. Cobalt is the magnetic impurity most soluble in ZnO. Therefore, numerous experimental groups have tried to grow ZnO semiconductors doped with ferromagnetic transition metals. But there is few report of electrodeposition applied to grow Co doped ZnO semiconductors. That is due to the ferromagnetic transition metal ions are difficult to dope into the ZnO crystal lattice successfully. In this paper, the Co doped ZnO thin films were prepared by electrdeposition with adding hexamethylenetetramine. The optical properties of the Co-doped ZnOare also studied.关键词：ZnO;hexamethylenetetramine;electrodeposition;photoluminescence100|82|1更新时间：2020-08-11
- 摘要：The semiconductor ZnO has grained substantial interests in the research community in part because of its wide direct band gap (3.3 eV) and large exciton binding energy (60 meV). It is a well-known piezoelectric and electro-optic material with potential applications such as optoelectronic and luminescent devices as well as chemical sensors. Even though the research focusing on ZnO goes back to several decades, one of the renewed interests is fueled by the observation of ferromagnetic behavior in transition metals doped ZnO which is called diluted magnetic semiconductors (DMS). DMS could be served as ideal material for exploiting spin in addition to charge in semiconductor devices. Much attention has been paid to the magnetic properties of ZnO-based DMS. In this paper we focused on the optical properties of Co-doped ZnO films. Highly (002) orientated Zn0.95Co0.05O films were deposited on Si (100) substrate using inductively coupled plasma enhanced physical vapor deposition (ICP-PVD) with magnetic confinement. X-ray diffraction pattern and typical Raman spectrum show that Zn0.95Co0.05O film has a wurtzite structure. Transmittance spectrum indicates that the Zn0.95Co0.05O film has an average transparency of over 80% in the visible and infrared wavelength. The band gap of Zn0.95Co0.05O film (3.11 eV) is less than that of pure ZnO, which is due to sp-d exchange interactions between the band electrons in ZnO and the localized d electrons of the Co2+ ions. Three obvious absorption peaks around 660, 615 and 560 nm are found. They are ascribed to derive from d-d transitions of tetrahedrally coordinated Co2+ and attributed to the 4A2(4F)→2E(2G), 4A2(4F)→4T1(4P), and 4A2(4F)→4A1(4G) transitions. The photoluminescence spectrum shows broad blue and green emission from the Zn0.95Co0.05O film at room temperature. On the other hand, no luminescence is found in the ultraviolet region near 380 nm.关键词：ZnO thin film;Co-doped;sputtering deposition;optical properties101|128|0更新时间：2020-08-11
- 摘要：ZnO has recently become a very popular material due to its great potential for optoelectronics applications. The large direct band gap of 3.3 eV, along with the large exciton binding energy (60 meV) and many other advantages, make ZnO a strong candidate for the next generation of ultraviolet light emitting and lasing devices operating at high temperatures and in harsh environments. The ZnO based light emitting diode (LEDs) will be brighter than the current state-of-art nitride light emitters, and at the same time, the production cost will be reduced significantly compared with current technology. The pulsed laser deposition (PLD) technique has been proved to be a very effective method to deposit high-quality films with complex composition. This technique has some other advantages such as deposition in controllable oxygen partial pressure, high controllability of film composition and growth process, and relatively high deposition rates. In this paper, the ZnO films were deposited on single-crystalline Si(100) substrates by pulsed laser deposition (PLD) method. X-ray diffraction (XRD),atom force microscope (AFM),transmission electron microscope (TEM)and photoluminescence (PL) spectrum measurements were employed for the investigation of crystal quality and light emitting performance. The dependence of crystal quality and photoluminescence performance on the growth temperature and oxygen partial pressure was investigated. The results indicate that high-quality ZnOthin films with perfect c-axis preferred orientation and smooth and dense microstructure have been successfully grown under optimized conditions (700℃, 20 Pa). The near-band-edge emissions in PL spectra are greatly enhanced and the deep level emissions are weakened with the increase of oxygen pressure due to the improvement of stoichiometry, the ZnO films grown under high O2 pressure (20 Pa) are well close to stoichiometry and of optically high quality. Therefore, it can be concluded that the PL spectra depend on the stoichiometry and the microstructure of the film. The achievement reported here will be used to control the optical properties of ZnOthin films for optical device applications.关键词：ZnO thin films;pulsed laser deposition;photoluminescence117|264|3更新时间：2020-08-11
- 摘要：Recently, zinc gallate (ZnGa2O4) phosphors have gained much attentions for use in vacuum fluorescent displays (VFD), thin film electroluminescent devices (TFED), field emission displays (FED) and low-voltage cathodeluminescence (LVC), because they exhibit higher chemical stability than sulfide phosphors. ZnGa2O4 is also expected as a new photoluminescence material. The influence of the ratio of n(Zn):n(Ga) on the structure and the photoluminescence properties of ZnGa2O4 was investigated mainly. Using our rich compounds of gallium, ZnGa2O4 with the nominal formula with ZnO/HGaO2 (n(Zn):n(Ga)) ratio ranging from 0.350 to 0.650 was prepared by high temperature solid-state reaction methods. ZnO-HGaO2 system compounds near the ZnGa2O4 stoichiometric composition have been tested with diverse characterization techniques. Fluorescence spectrophotometer was used to measure the photoluminescence excitation and emission spectra of ZnGa2O4. X-ray diffraction measurements were performed to investigate the phase states in the ZnGa2O4 phosphors dependent on the mixture molar ratio of ZnO and HGaO2. Thermal analyzer was used for recording TGA-DTA curves of ZnGa2O4. The results show that ZnGa2O4 has a spinel structure, consists of a cubic cell with Fd3m symmetry, which contains a close-packed array of 32 oxygen atoms with cations in tetrahedral and octahedral interstices. The excess Ga or Zn is soluble in ZnGa2O4 and don't affect the spinel lattice of ZnGa2O4. The lattice constants increased along with increasing of n(Zn):n(Ga) ratio. When Zn excess, the formula of ZnGa2O4 changed into Zn(Ga1-xZnx)2O4,this formula leaded to the increase O2- vacancy. When Ga excess, the formula of ZnGa2O4 changed into (Zn1-xGax)Ga2O4,this formula leaded to the increase Zn2+ vacancy. ZnGa2O4 is a new n-semiconductor material, its lattice interval exist the vacancies and ions, belong to structure defect or crystal defect. The luminescence mechanism is similar the luminescence of semiconducter, with an optical band gap of 4.4 eV. ZnGa2O4 is a kind of self-activated luminescence material with two self-activated optical center, e.g. [Td(Ga—O)] and [Oh(Ga—O)], its excitation and emission spectras are wider. In n(Zn):n(Ga)≤0.500, the absorption band at 248 nm and the fluorescence band at 367 nm originated from self-activation optical centers of the tetrahedral [Td(Ga—O)] in the spinel lattice. In n(Zn):n(Ga)≥0.550, the absorption and the fluorescence band at 270 nm and 441 nm originated from self-activation optical centers of the octahedral [Oh(Ga—O)] in the spinel lattice. The peak of excitation and emission shifted to longer wavelength when n(Zn):n(Ga) ratio between 0.500 and 0.550. TGA-DTAanalyses showed ZnGa2O4 had excellent chemical stability properties. These results can help improve understanding ZnGa2O4 or doped ZnGa2O4 phosphors for the application research with high brightness.关键词：ZnGa2O4;n(Zn)：n(Ga) ratio;crystal structure;photoluminescence111|70|2更新时间：2020-08-11
- 摘要：The lattice vibrations of the MOCVD-GaxIn1-xAsyP1-y epilayers and MOCVD-GaxIn1-xAsyP1-y /InP Distributed Bragg reflectors(DBRs) are investigated by micro-Raman scattering techniques. The used DBRs samples were formed with Ga0.4In0.6As0.85P0.15/InP alternative layers grown on the S-doped high quality (100) InP substrates in an atmospheric or low pressure metal organic chemical vapor deposition(MOCVD) system made up in our laboratory. The lattice constant and composition parameters(x,y) were determined using double crystal X-ray diffraction, scanning electronic microscope-photoelectron spectra and photoluminescence(PL) measurements. Raman spectra were measured at room temperature using the 488 nm line of Ar ion laser as an exciting source. The Raman signal was collected in the near back-scattering configuration and analyzed with a monochromator. The Raman spectra exhibit three major modes of vibrations in the quaternary alloy Ga0.4In0.6As0.85P0.15 grown on the InPsubstrates. They are attributed to InAs-like, GaAs-like and GaInP-like, respectively. The Raman spectra line-shape of the three major modes of vibrations clearly changed with the increasing of period number of DBR. The intensity of the InAs-like vibration is not changed, but its full width at half-maximum(FWHM) narrowed, the peak value location moved in the direction of the low-frequency. The intensity of the GaAs-like and GaInP-like gradually weaken. Ratio of intensities of InAs- and GaAs-like vibrations increased with the increasing of period number of DBR. The quaternary alloy Ga0.4In0.6As0.85P0.15 was in the region of immiscibility. It was found that the surfaces of the samples grown in the region of immisicibility are rough. The interface quality between the Ga0.4In0.6As0.85P0.15 and InPwas effected. The restrictive effect of the phonon in the Raman scattering investigations showed that the non-integrity crystalloid appeared during the growth of the multi-layer structure.关键词：MOCVD-GaxIn1-xAsyP1-y/InP;distribution Bragg reflector structure;raman scattering;lattice vibration107|60|0更新时间：2020-08-11
- 摘要：The optical properties of GaN-based materials are essential to the optoelectronic devices such as light emitting diodes and laser diodes in visible and ultraviolet regions. In this work unintentionally doped GaNand Mg-doped p-GaN were grown on sapphire substrates by plasma-assisted molecular beam epitaxy (PA-MBE ). The photoluminescence (PL) characteristics were studied by means of RT and low-temperature PLspectra with λex=325 nm. The electrical properties of GaN:Mg were tested by Hall measurement. We especially studied the yellow luminescence (YL) observed in PLspectra in view of the difference between these two types of GaN. In as much as the exciton peaks of Ga-rich GaN exhibit a narrower FWHM than N-rich GaN, it is indicated that material quality of the former is better than the latter. The YLin Ga-rich GaNis related to point defects which is correlative with nitrogen vacancies. Mg doping concentration has a great effect on PLcharacteristics of p-GaN. The p-type samples show three shapes of PLlines with Mg-doping temperature varying. Hall measurements show that hole concentration of p-type GaNis increased up to a upper limit and then decreased along with the increasing of Mg doping temperature. In combination with the results of hall test, we proposed that the YLin highly Mg-doped GaNcould be attributed to self-compensation effect and the decrease of crystal quality caused by highly Mg doping. Through the study, we found that the YLoriginates from different sources by comparing the undoped GaN and Mg-doped GaN, and it also correlates with the material qualities commonly.关键词：MBE;Ⅲ/Ⅴ ratio;PL spectra;yellow luminescence135|211|0更新时间：2020-08-11
- 摘要：Zn1-xFexO(x=0.01,0.05,0.10) compounds were fabricated by the sol-gel method. The X-ray diffraction patterns show that the wurzite structure does not change for all doped-ZnO samples. Furthermore, we could not find any Fe cluster or phase separation in the X-ray diffraction patterns. The photoluminescence of Fe-doped ZnOwith different solution concentration, annealing temperature and Fe dopant concentration were investigated. Thermal annealing improved the optical quality of the doped-ZnO. The low Fe content doped-ZnO with 0.1 mol/L-solution concentration exhibits improved photoluminescence.关键词：Fe;ZnO;XRD;PL105|139|1更新时间：2020-08-11
- 摘要：To research the photoluminescence mechanism of nanocrystalline silicon (Si) and to give some experimental backing for the fabrication of Si light emitting devices, we tried to make Porous Anodic Alumina Template (PAA) by using a two-step anodization technique. The pulsed laser deposition (PLD) was used to deposit a layer of Si on the PAA substrate through a two-step deposition procedure in vacuum.After that, we got a combined film of Si and PAA. Next, put the combined film into acid solution to get rid of the PAAsubstrate. Then we got the Si film with Si nanowires scattered on it. Scanning electronic microscopy (SEM)and X-ray diffraction (XRD) were used to study the structure, morphology, crystalline phase and the composition of the film. The result showed that this Si structure is amorphous phase. The diameter of the nanowires is about 67.5 nm, the length is about 100 nm, the number density is about 1011/cm2. This Si film possess of very large surface, so surface state and the substances it adsorbed played an important role in photoluminescence.The photoluminescence spectrum could be decomposed into two parts. One is a broad emission band whose peak wavelength was about 610 nm with a full width of half maximum (FWHM) is about 150 nm. The other included 17 sharp peaks, each of them has fine structure. The wavelength intervals between the sharp peaks are different, but the energy intervals are equal.We analyzed the structure characteristics of the sample and used the Quantum Confinement Effect model and the Surface Photoluminescent Center model to explain the photoluminescence spectrum. Accordingly, there are two luminescence processes: 1. Electron-hole pairs recombined in the Si nanocrystallines and the photons pass through the surface to come out. When the samples were excited by laser (488 nm),it produced a great deal of electrons and holes. After some relaxation process, quite a few electrons and holes recombined in the Si nanocrystallines and give off light which forms the broad peak of the spectrum whose peak wavelength was about 610 nm and the FWHMwas about 150 nm. 2.An electron (or a hole) relaxed to the surface luminescence center and recombined with a hole (or an electron) and gave off light. In this way, the photons came out from the surface luminescence center directly. When the sample was excited by laser (488 nm), it produced a great deal of photon generated carriers. Because of the quantum confinement effect, the band-gap energy of Si nanocrystallines was increased to the visible light range. The energy of the photon generated carriers is also in the visible light range. Some of the photon generated carriers wouldn't stay inside; they came to the surface by diffusion. During the diffusion process, they would come into collision with atoms and electrons, so they would lose energy gradually.This is a relaxation process in fact. They would be captured by the surface luminescence center in the end. As the surface luminescence center was vibrating, so the intervals between excited energy levels were equal.We also proposed a new energy band model and even calculated the quantum numbers of the excitation bands which correspond to the small sharp peaks.关键词：Si nanowire;porous anodic alumina template;pulsed laser deposition;photoluminescence103|118|0更新时间：2020-08-11
- 摘要：Recently, low-dimensional structures, such as nanowires, nanoslices and nanotubes, have aroused remarkable attentions due to a great deal potential applications in data storage, advanced catalyst, photoelectronic devices etc. In this paper nanowires were prepared by the hydrothermal method. Appropriate amounts of high purity Gd2O3, Yb2O3 and Er2O3 were dissolved into concentrated HNO3 solution. Diluted NaOH solution was dripped into the solution to adjust the pHvalues for an appropriate value. After well stirred, the resultants of RE(OH)3(RE=Gd, Yb, Er) colloidal solution was heated and then was centrifuged and dried. The dried RE(OH)3 powders were calcined, and finally Gd2O3:Er3+/Yb3+ nanowires and nanoslices were obtained. The morphology and size of nanowires were obtained by transmission electron micrograph and X-ray diffraction patterns. By controlling the pHvalues, the shape of the nanocrystals varied from two-dimensional nanoslices to one-dimensional nanowires. It was found that the nanoslices were yielded in the chemically neutral conditions and nanowires were yielded in the alkalescent conditions. Emission spectra were studied under the 980 nm diode laser pumping. Green upconversion luminescence of 2H11/2/4S3/2→4I15/2, red upconversion luminescence of 4F9/2→4I15/2 and infrared emissions of 4I13/2→4I15/2 were observed. The infrared emissions of 4I13/2→4I15/2 gradually decreased with the increase of pHvalue and the forming of nanowires, while the visible upconversion luminescence of 2H11/2/4S3/2→4I15/2 and 4F9/2→4I15/2 gradually increased, indicating more efficient upconversion luminescence. The relative intensity of the green emissions to the red emissions also increased with the increase of pH value. Electronic relaxation processes dominates the intensity ratio of the upconversion luminescence to the infrared emissions. The ratio of surface atoms to inner atoms in nanowires was decreased in comparison to that in nanoslices, and the nonradiative relaxation was decreased due to a great number of surface defects involved. This led the intensity of upconversion luminescence to increase and the intensity of infrared emission to decrease relatively in nanowires.关键词：nanowires;nanoslices;intensity ratio;surface defects107|60|5更新时间：2020-08-11
- 摘要：ZnO is a wide band gap semiconductor (3.37 eV) with higher excitation banding energy of 60 meV. ZnO one-dimensional materials have stimulated much attention due to the promising potentials in extensive applications, ranging form surface acoustic wave filters, optoelectronic devices, and light-emitting diodes. Many techniques have been used to grow ZnO nanowires, such as pulsed laser deposition, metal-organic chemical vapor deposition and template against anodic alumina membrane. Among the various techniques VLS (vapor-liquid-solid) method is favored for the simplicity and high quality products. This method often uses some of catalysts such as Au, Cu, Sn or other additives assist are often used in this method to control the growth process. There were reports about the syntheses of 1D ZnO nanowires arrays via a VLS process. However there is still the difficult problems about the controllable growth of the ZnOnanowires. We obtained ZnOnanowires through VLS method and researched controllability and growth mechanism of ZnO nanowires. ZnO powders were used as source material and the experiment was performed in a horizontal tube furnace. ZnO powders were spread in an alumina boat and place at the center of the furnace tube with temperature of 1350℃. Si(100) substrate covered with Ag catalysts was put down stream with the temperature of 400~800℃ for 30 min. Ar gas (40 sccm: standard cubic centimeter mass) was used as the carrier gas. The prepared nanowires were investigated by X-ray diffraction. The morphology and size distribution of the nanowires were characterized using SEM. Clearly the ZnO nanowires grown at substrate temperature ringing 600~700℃ are highly crystallized and exhibit a typical wurtzite structure. SEM showed that temperature of substrate has important influence on diameter and length of the ZnO nanowires. It was controllable that we can realize the ZnO nanowires growth through the catalyst and temperature. We have not seen that catalyst particle is on the top of ZnO nanowires, it is different from traditional VLS mechanism. The growth mechanism of ZnO nanowires was proposed.关键词：ZnO nanowires;VLS growth mechanism;catalyst;growth mechanism124|110|2更新时间：2020-08-11
- 摘要：Recently, there is much interest in the development of wide band gap semiconductor nanowires, because the cylindrical geometry and strong two-dimensional confinement of photons, electrons, and holes make them particularly attractive as potential building blocks for nanoscale optoelectronic devices. Semiconductor nanostructures with modulated composition have been known to enhance new functions and properties, such as GaAs/GaP uperlattice, core-shell structured Si-Ge nanowires, and core-shell Zn-ZnO nanobelts. To composite nanowires, especially, coaxial nanocables will provide a great possibility to take advantage of different function and properties of different material within a single nanoscale component. Aligned coaxial nanocables were grown on Si substrates by a vapor deposition technique. Zn powders were placed on a quartz boat and positioned at the center of a quartz tube in a horizontal furnace. After the quartz boat was inserted, the furnace was ramped to 1100℃ and kept at that temperature for 2 h under a N2 flow rate of 500 sccm. The obtained nanocable arrays had average diameters of about 100 nm and length up to more than10 μm. Both the shell thickness and the core radius were almost the same, about 25 nm. It has been revealed that the nanocable is grown from the sprout-shaped root and the top ends of the nanocables were typically round without droplet. Together with the XRD pattern and EDS mapping analysis, it can be suggested that the nanocable had a Zn2SiO4 shell and a Zn core. Aunique growth mechanism was proposed for the homogeneous crystallization of Zn-Zn2SiO4 core-shell nanocables. The CL spectra exhibited three distinct peaks: one strong peak at middle-UV region(300 nm) and another two weak bands at visible(560 nm) and infrared(865 nm) regions. The UV emission was attributed to the thin double-layer structure in the Zn-Zn2SiO4 core-shell nanocable where the Zn2SiO4 shell has the potential to serve as more ideal luminophors.关键词：nanocables;middle ultra-violet emission;growth mechanism94|78|0更新时间：2020-08-11
- 摘要：The electroluminescent polymer-metal complexes constitute an important class of functional materials and have found widespread use in the polymer light-emitting diodes(PLED). In recent years, they have become a new and fascinating area of research and attracted great interest as future flat-panel displays in the global and obtained the prodigious progress. As we known, there are two traditional approaches to obtain electroluminesent metalloquinolate thin films: vapor deposition in vacuum from the small molecules and filmcasting from the solution of the metalloquinolate-doped polymers. However, morphological changes during thermal treatments lead to partial crystallization of layered structure that ultimately results in device failure. Although the metalloquinolate-doped polymers can overcome these problems, current limitations are their heterostructures, which will affect device efficiencies and lifetimes. The metalloquinolate-contianing polymers that the covalent bond formatted between 8-hydroxyquinoline metal complexes with polymers for electroluminescence applications in PLEDshould combine the fluorescent properties of metalloquinolate and the processability of polymer. Anew method to synthesize 8-hydroxyquinoline lithium (Liq)-containing polymers were reported. Aseries of model polymers containing 8-hydroxyquinoline ligands were obtained by free-radical copolymerization with methyl methacrylate (MMA), styrene(S). High molecular weight polymer-lithium complexes were simply prepared by coordinating reaction of model polymers with lithium hydroxide. It is linear without cross-linking and can be dissolved easily in the common solvents, such as tetrahydrofuran(THF), and N,N′-dimethyl formamide(DMF). The method is fit to synthesize most of 8-hydroxyquinoline metal chelates-containing polymers by change the polymer chains or metal central ion. Their structures and performances were confirmed by NMR, FTIR, ultraviolet-visible absorption, photoluminescence spectrum, DSC, TGAand gel permeation chromatography analysis. Ultraviolet-visible absorption and PL emission spectra are consistent with that of small molecular weight Liq complexes that show the luminescence of polymers is nothing to do with polymer segments, but due to containing Liq functional group. The solvents, such as THF, affected the conjugated electrons in quinolinolate group and made the spectra of polymers a red shift obviously.关键词：8-hydroxyquine lithium complex;polymer light emitting devices (PLED);methyl methacrylate;styrene;polymer synthesis94|105|1更新时间：2020-08-11
- 摘要：The first demonstration of light amplification in silicon represents a significant milestone towards producing fully integrated monolithic photonic chips. Stimulated Raman scattering has been used to demonstrate light amplification and lasing in silicon. The nonlinear optical loss associated with two-photon absorption (TPA)-induced free carrier absorption (FCA) is the main limitation to amplify the laser. With introducing a reverse-biased p-i-n diode embedded in a ridge silicon waveguide, when a reverse bias voltage is applied to the p-i-n diode, the TPA-generated electron-hole pairs can be swept out of the silicon waveguide by the electric field between the p- and n-doped regions. Thus the effective carrier lifetime, representing the lifetime of the free carrier's interaction with the optical mode in the waveguide region, reduces with increasing bias voltage. Because the technics on silicon has been very mature and apparatus made in silicon is very smart, it is a good method to apply the silicon as the waveguide to reduce the volume of laser amplifier. There is no restrict of pump power resource for the Raman laser amplifier based on silicon waveguide. It also possess further higher saturate power. We design a new type of Raman laser amplifier based on silicon waveguide by coating the transmissive film to the cleavage of silicon waveguide according to the Fabry-Perot resonance technique and traveling wave amplifier theory. The Raman gain coefficient can be controlled by the reverse bias voltage on the silicon waveguide, and the amplified signal light wavelength responses to the pump light wavelength in the Raman laser amplifier. The lifetime of photo-generated carriers in silicon-on-insulator rib waveguides is studied in connection with the optical loss produced via nonlinear absorption. We present an analytical model about the Raman gain by using the conclusion that effective carrier lifetimes of 1 ns can be obtained in waveguides resulting in negligible nonlinear absorption. The Raman gain and output power of the amplifier is calculated by the equation we constructed. For a 4.8 cm long waveguide with an effective core area of ~1.6μm2 and a reverse bias voltage of 25 V, we obtained a net gain of 2.6 dB with a pump laser wavelength of 1536 nm and a pump power of 600 mW inside the waveguide. Raman gain can be raised by increasing the waveguide length and pump power properly.关键词：Raman laser amplifier;stimulated Raman scattering;PIN silicon waveguide;two photon absorption110|118|0更新时间：2020-08-11
- 摘要：Broadband optical sources with short coherence length, low spectral ripples and high spectral intensity are desirable for various applications such as fiber-optic gyroscope (FOG), optical noise sources in EDFA measurement systems, optical sensor systems, spectrum-sliced sources and component testing sources to sliced spectrum sources for lower-cost access networks. Such a source must be broadband in order to reduce errors due to coherent backscattering, polarization cross coupling and the Kerr effect. Sources based on the amplified spontaneous emission (ASE) from an erbium-doped fiber are promising than light emitting diode (LED) and superluminescent light emitting diode (SLED) because of the high output pump, broadband, and spectrum stability. The power produced by the superluminescent diode and LED is also difficult to couple into single-mode fibers. Superfluorescence sources(SFS) on the ASE from an erbium-doped fiber are attractive because of the intrinsic broad emission spectrum and the high output power can be generated easely using semiconductor LD pumps. The SFSdesigner can control the source spectrum, stability and power through a choice of source configuration, pump power, and fiber length. Various configurations have been considered for the SFS system, depending on the presence of reflections from the fiber ends as well as the propagation direction of the pump wave relative to the propagation direction of the utilized source output. SFSs with two nonreflecting ends are single-pass devices, while those with a reflector at one end are double-pass devices. The output from the pump end of the SFSis the backward signal, while the output from the opposite end is the forward signal. The experimental results using double-pass forward configuration on high erbium-doped fiber SFS pumped by 980 nm laser diode are reported. The maximum superfluorescent output power is 10.8 mW with the slope efficiency of 10.6%, while pump power is 380 mW. The power stability is 0.02 dB in 1553.1~1588.6 nm near 36 nm range, 3 dB bandwidth is 84.2 nm.关键词：fiber superfluorescent source;high erbium-doped fiber;L-band;double-pass forward115|177|1更新时间：2020-08-11
- 摘要：The microchannel plate (MCP) ion barrier film's stopping function on incident positive ions in the third generation low-level-light imaging tube was introduced. The concepts of nuclear stopping power, electronic stopping power and average range were also introduced, the micrographs of unfilmed MCP and MCPs filmed with different thicknesses were shown. Using Tomas-Fermi shielding potential, we analyze and discuss this problem and a Monte-Carlo simulation was peromed. Analytical expressions and corresponding nuclear and electronic stopping power curves have been shown. Quantitative results were given, reflecting the stopping function of Al2O3 and SiO2 films when nucleus and electrons impinge perpendicularly with different energies. Table 1~3 show the corresponding technical data. The conclusion is that the stopping power of Al2O3 film is stronger than that of SiO2, and the selection of Al2O3 ion barrier film is reasonable and feasible. After the theoretical analysis and experimental simulation, the conclusions are brought forward as follows:The stopping function of ion barrier film on the incident ions can be described by two concepts of nuclear stopping power and electronic stopping power. When the thickness of the films is constant, the range of the ions with the same energy in Al2O3 films is two to three times as short as that in SiO2 films. It is indicated that the capability of the stopping function of Al2O3 films is higher than that of SiO2 films. From the calculated results of the stopping function of the films on the ions, it is obviously concluded that the capability of nuclear stopping function on the ions is higher than that of electron, which is in agreement with LSStheory. When 9999 oxygen ions with the energies of 100, 300, 500 eV are perpendicularly incident to the Al2O3 film with 5 nm thickness, no transmitting ions are observed. While in the same conditions, 34 and 629 oxygen ions with the energies of 300 eVand 500 eV, respectively, can pass through the SiO2 films with 5 nm thickness, i.e. the maximal transmittance is 6%. In brief, the capability of the stopping function of Al2O3 films is higher than that of SiO2 films, resulting from that Al2O3 films are high density and the fiber rigidity of Al2O3 films is close to that of corundum; while SiO2 is atom crystal, and the rigidity of SiO2 films is equivalent to that of crystal and inferior to that of Al2O3.关键词：microchannel plate;ion barrier film;nuclear stopping;electronic stopping;Monte-Carlo simulation109|131|1更新时间：2020-08-11
- 摘要：Owing to the highly transitory behaviour of laser-produced plasma, it is difficult to found the mechanism of plasma radiating because of the process of ablation being complicated.It is the most important to characterize the laser produced plasma (LPP)in a time- and space-resolved way. In the paper,optical emission spectroscopy is used to characterize the plasma produced by 308 nm,20 ns XeCl excimer laser ablation of Cu target in low pressure. Time- and spatial-resolved measurements of optical emission produced by XeCl excimer laser ablation of Cu in low pressure were reported. The pressure of ablation chamber was 1 Pa air. The temporal variation of the spectrum lines intensities was analyzed.The plasma plume photograph from XeCl excimer laser ablation of Cu was taken by camera in air with pressure of 1 Pa. The experimental results show that the plume has different colour in different region,the core region of the plume is white, the middle region of the plume is yellow and purple etc, the outskirts region of the plume is green.The experimental results may be explained using a theory model based on that plume is made of three region and the region detail species excitation mechanism is different from each another. The continuum background emission comes from the Bremsstrublung emission of electrons ejected from target. The excited copper atoms and ions may be produced from different mechanism, the atoms excitation mechanism in plume is electron collision energy transfer and recombination of electron and ion, but the ions excitation mechanism in plume is electron collision energy transfer only. The results show that the most possible plume radiation mechanism is dual excitation model,it can be used to explain the experimental results that the simple excitation model can to do, and can be used to explain the experimental results that the simple excitation model can not to do. We found that the plume radiation mechanism obtained in low pressure is accuracy and direct to that of at the pressure of one atmosphere.关键词：laser ablation;laser inducement;time-resolved spectra;plasma;copper112|127|0更新时间：2020-08-11
- 摘要：p-type ZnO has attracted more and more attention because it is necessary to fabricate ZnO devices based on current injection. More and more improvements on p-type ZnO and p-n junctions are reported. However, electroluminescence in these works was rarely observed. We have already succeed in fabricating a ZnO p-n junction LED on sapphire substrate by using activated NO plasma. Here, N2 was used as the acceptor dopant and O2 was used as assistant gas as well as oxygen source. Emission spectra of the N2-O2 plasma were monitored in situ to adjust parameters timely. Electronics measurements of the as-grown p-type ZnO on sapphire shows a carrier concentration of 1.2×1018cm-3 and mobility approach to 1 cm2·V-1·s-1. The LED based on p-n junction shows a certain rectification effect and the turn on voltage is 3.10 V, which is consistent with the bandgap of ZnO. Electroluminescence spectra shows two bands: one is at 420 nm, from donoracceptor pairs; and the other ranges from 500 to 700 nm, which is attributed to the emissions from point defects in ZnO.关键词：ZnO;LED;N-doped136|91|1更新时间：2020-08-11
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