最新刊期
卷 31 ， 期 5 ， 2010
- 摘要：Thin ZnO films were grown on silicon (111)/sapphire substrate via pulsed laser deposition technique and then some of the samples were treated with different rapid thermal annealing (RTA) conditions, such as annealing temperature ranging of 500 to 900 ℃ and annealing ambience(nitrogen and oxygen). Finally, these samples were characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), IR and photoluminescence (PL), respectively. It was observed that the quality and the grain size of thin ZnO films increased after annealing. Moreover, at the same lower annealing temperature, the films annealed under nitrogen ambience showed better qualities and few oxygen vacancies than those annealed under oxygen ambience. The experiment showed that the best annealing temperature under nitrogen ambience was 900 ℃ and the optimum annealing temperature under oxygen ambience was 800 ℃. Furthermore, as oxygen vacancies decreased, stronger green photoluminescence was detected, possibly related to the contents of the oxygen vacancies.关键词：thin ZnO films;rapid thermal annealing;photoluminescence;XPS;oxygen vacancies125|303|3更新时间：2020-08-12
- 摘要：The technique of photoluminescence(PL) spectra is an important method for studying the properties of semiconductors and quantum wells since its high sensitiveness, convenience and non-destructive. This technique was used to study the single quantum well(QW) of In0.2Ga0.8As/GaAs in this paper.Different PL spectra were reported under different temperature,which ranged from 125 K to 260 K for a certain sample, and the PL spectra of the samples with different quantum well width were also reported.The paper reported that, for a certain sample, the peak of its PL spectra moved towards long wavelengh ranges with the temperature increa-sing,which means that the band gap of the SQW becomes narrower. Detail consideration suggested that this property was able to be described by the equation of Varshni for the bulk materials. So, the SQW is similar to its bulk material at this point. This was mainly because within certain thickness of SQW, there was no lattice misfit dislocation, and the fundamental structure of the energy gap will not change. It was also reported that, at certain temperature,the narrower was the SQW, the wider was its band gap. We performed a brief calculation by solve Schrdinger equation,and found that the experimental result fitted to the theoretical calculation.The relationship between full width at half maximum (FWHM) of PL peak and temperature of a certain sample and the relationship between (FWHM) and SQW width of different samples were also reported, at the same time, theoretical explanation was presented for these phenomenon.关键词：In0.2Ga0.8As/GaAs;SQW;PL spectra;temperature;FWHM132|58|2更新时间：2020-08-12
- 摘要：c-plane sapphire substrate was etched chemically in the molten KOH solvent at a high temperature with different time, the surface microscopy of pre-treated sapphire substrate was obtained by SEM (Scanning Electronic Microscope) and AFM (Atomic Force Microscope), followed with the epitaxial GaN on sapphire substrate etched with different etched time. The quality and the microscopy of the epitaxial GaN were characterized using XRD (X-Ray Diffraction) and AFM. Discussion was processed about in which way the etching time affecting the material grown on pre-treated sapphire substrate.关键词：patterned sapphire substrates;metal-organic chemical vapor deposition;GaN113|140|2更新时间：2020-08-12
- 摘要：Based on the framework of effective-mass approximation and variational approach, the binding energy of a hydrogenic donor impurity state is investigated theoretically as functions of the impurity position and the quantum dot size by employing a trial wavefunction with two variational parameter for a cylindrical wurtzite GaN/AlxGa1-xN quantum dot(QD) with finite potential barriers. The numerical results show that the donor binding energy of the hydrogenic impurity is highly dependent on the impurity position and QD size. When the built-in electric field is ignored or considered, the donor binding energy has a maximum value with moving the impurity position along the growth direction. The donor binding energy increases firstly, reachs a maximum value, then decreases with increasing the height and the radius of QDs. The strong built-in electric field induces an asymmetrical distribution of the donor binding energy with respect to the center of the QD. In particular, we find that the donor binding energy is insensitive to the dot height when the impurity is located near the top boundary(z0=L/2,z0=L/4)of the WZ GaN/AlxGa1-xN QD. And we compare the above results with previous calculation results using different trial wavefunction. The present results using two variational parameter wavefunction is better than the results given by previous two-parameter wavefunction. A good agreement between the present results using two variational parameter wavefunction and the results of the wavefunction with one variational parameter is found. Using the binding energy obtained from the present calculations, we further calculate the virial theorem number as a function of the quantum dot radius. Our present result coincides with the previous finding, so we may say that the present trial wavefunction with two variational parameter can describe better the internal motion of hydrogenic donor impurity state in the cylindrical wurtzite QD.关键词：cylindrical quantum dot;hydrogenic donor impurity;built-in electric field;virial theorem number107|117|1更新时间：2020-08-12
- 摘要：Application of semiconductor nanostructure materials in devices has become one of the major focuses in recent nanoscience researches. And considerable effort has been made to fabricate the zinc oxide (ZnO). With its large exciton binding energy of 60 meV, ZnO has been recognized as a promising photonic material in the shortwavelength region with significant potential in laser emission, field emission, and nanoscale heterojunction. Electrodeposition of polycrystalline semiconductor is mainly used for photovoltaic and optoelectronic applications. It is a simple and inexpensive technique compared to molecular beam epitaxy (MBE), liquid phase deposition (LPD), or chemical vapor deposition (CVD). Granular systems consisting of nanoscale ferromagnetic clusters imbedded in a semiconductor matrix have been recently realized using low temperature MBE by ion implantation/annealing, or simple annealing. As an alternative to this approach, we have investigated the electrodeposition of semiconductor-based systems consisting of Mn2+ in a ZnO semiconductor host.In this paper, we present the results of structural and optical properties of Mn doped ZnO nano columns electrodeposited onto p-type Si (111) substrates. Mn2+-doped ZnO nanocolumns have been successfully grown by electrodeposition method on Si substrate. The columns are 500~600 nm long with diameters ranging in 200~300 nm. X-ray diffraction (XRD) and X-ray photospectroscopy (XPS) studies suggeste that the Mn ions dope into the ZnO crystal lattice. The concentration of Mn ions is 2%. In the resonant-Raman spectrum, phonon frequency shifts to higher wavenumbers. In photoluminescence spectrum, a weak ultraviolet emission and a strong visible emission are observed.关键词：ZnO columns;electrodeposition;resonant-Raman103|80|0更新时间：2020-08-12
- 摘要：MgZnO films with highly c-axis orientation have been prepared on silicon (100) substrates via the excimer laser PLD method. The morphologies, structures, components, and optical properties have been systemically characterized by SEM, XRD, XPS, PL and absorption measurements. It has been found the oxygen pressure plays an important role in determining the structure and optical properties of the MgZnO film. The film grown at 15 Pa exhibits a unique nanocrystal structure with very high optical quality. It has been found that the UV emission peak is blue-shift about 86 meV with the oxygen pressure increaseing from 5 to 45 Pa due to the increased solubility of Mg in MgZnO films. As for the green emissions located between 500~600 nm, they can be attributed to the deep-level emission of oxygen related defects. Our work will be of benefit to the further research to prepare epitaxial layer for growing ZnO nanoarrays by PLD technique.关键词：MgZnO films;oxygen pressure;blue shift98|99|0更新时间：2020-08-12
- 摘要：The fluorescence characteristic of the CPLX-Y3+ complex system was studied in this article. Y3+ can significantly enhance the fluorescence intensity of the system, and accordingly we established a new sensitive analytical method to determine ciprofloxacin. The influencing factors of the CPLX-Y3+ fluorescence intensity were thoroughly studied, and the fluorescence enhancement mechanism was preliminary discussed. In the buffer solution of tris-HCl (pH=5.5) with 5.0 × 10-5 mol /L of Y3+, the concentration of CPLX and fluorescence intensity of the system showed good linear relationship. The linear range is 1.0×10-9~2.0 ×10-6 mol/L, and the detection limit is 3.1×10-11 mol/L(S/N=3). This method can be directly used to determine the CPLX of human urine and CPLX tablet.关键词：yttrium (Ⅲ);ciprofloxacin (CPLX);fluorescence;urine;tablet106|82|1更新时间：2020-08-12
- 摘要：A tandem organic light-emitting diode (OLED) with a new charge generation layer of m-MTDATA:MoO3 has been studied. Compare to the OLED with single electroluminescence unit, the tandem OLED shows an enhanced luminance and current efficiency by a factor of nearly 1. The maximum luminance and the maximum efficiency of tandem OLED are 83 210 cd/m2 and 30.06 cd/A, respectively.关键词：charge generation layer;p-i-n;tandem;OLED102|85|0更新时间：2020-08-12
- 摘要：The electron injection mechanism of the effective cathode structure has been investigated, doping cesium carbonate (Cs2CO3) into the organic electron-transport layer, which significantly enhances the electron injection in comparison with an ultra-thin Cs2CO3 injection layer, with a notable superiority in both luminance and efficiency. The results show that Cs2CO3 doped tris-(8-hydroxyquinoline) aluminum(Alq3) /Al cathode exhibits better electron injection efficiency than that in Cs2CO3/Al bilayer cathode, thus a maximum current efficiency of 6.5 cd/A (3.1 cd/A for Cs2CO3/Al) is obtained for 30% Cs2CO3 doping concentration device. It is proposed that this improved efficiency is related to the greatly enhanced electron injection at the Alq3 ∶ Cs2CO3/Al cathode interface and efficient electron transport in the bulk of the Cs2CO3 ∶ Alq3 layer. The result from atomic force microscopy shows that with the insertion of Alq3 ∶ Cs2CO3 layer, the roughness of Alq3 surface decreases, which is favorable to improve the device luminance and increase the device lifetime.关键词：organic light-emitting diodes;cesium carbonate;electron injection;electron transport104|89|1更新时间：2020-08-12
- 摘要：In this work, ten complexes of europium, terbium and dysprosium with p-chroro-benzoic acid and 2,4,6-tris-(2-pyridyl)-s-triazine (TPTZ) were synthesized and characterized by elemental analysis, rare earth coordination titration and inductively coupled plasma atomic emission spectrometry (ICP),the results showed that the complexes have the composition of Eu(p-ClBA)3(TPTZ)·2H2O; Tb(p-ClBA)3 (TPTZ)·3H2O and Dy(p-ClBA)3(TPTZ)·2H2O; Eu0.5La0.5(p-ClBA)3(TPTZ)·2H2O,Eu0.5Gd0.5 (p-ClBA)3 (TPTZ)·2H2O,Eu0.5Y0.5(p-ClBA)3(TPTZ)·2H2O,Tb0.5La0.5(p-ClBA)3(TPTZ)·2H2O Tb0.5Gd0.5(p-ClBA)3-(TPTZ)·2H2O, Tb0.5Y0.5(p-ClBA)3(TPTZ)·2H2O and Dy0.5Gd0.5(p-ClBA)3(TPTZ)·2H2O. The molar conductivity indicated that all the complexes are non-electrolytes. The ligands and the complexes were studied by the means of IR spectra, UV spectra, fluorescence excitation and emission spectra. The results showed that p-chroro-benzoic acid is bonded with rare earth ions through oxygen atoms in the carboxyl group; 2,4,6-tris-(2-pyridyl)-s-triazine through the three nitrogen atoms coordinate with the rare earth ions. The red shift in UV absorption spectra of the complexes is observed, substantiating that a more extensive π-π* conjugating system is formed due to the coordinated reaction. The fluorescence emission intensity of Eu(p-ClBA)3(TPTZ)·2H2O is the strongest compare with other two rare earth complexes . But, the fluorescence emission intensity of Tb0.5La0.5-(p-ClBA)3(TPTZ)·2H2O is the strongest in the doped rare earth complexes. The doped rare earth ions (La3+, Gd3+ and Y3+) can sensitize the luminescence of the complexes, it showed that a part of dinuclear complexes are formed.关键词：p-chloro-benzoic acid;2;4;6-tris-(2-pyridyl)-s-triazine;rare earth complexes;doping116|95|0更新时间：2020-08-12
- 摘要：A ligand on Schiff base, N,N'-bis(2-hydroxy-1-naphthylidene)-o-phenylenediamine, and its zinc complexes were synthesized. Its structure was investigated by MS, elemental analysis, FTIR spectra, TG-DTG curve; through UV-Vis absorption spectroscopy, fluorescence excitation and emission spectra the photophysical properties of the complexes were studied. The results showed that the ZnL's thermal decomposition temperature was 433.2 ℃, with very good thermal stability; in DMF solution system, the UV absorption band of ZnL complex was in the ranges of 250~500 nm, with fluorescence excitation in the ranges of 343~493 nm. The orange-red fluorescence emission peak wavelength was at 626 nm, the best excitation wavelength was 470 nm, and the band gap was 2.32 eV.关键词：Schiff base;zinc complexes;spectral characteristics106|75|1更新时间：2020-08-12
- 摘要：Anodic aluminum oxide (AAO) samples have been prepared by using electrochemical anodizing technique in oxalic acid,sulfuric acid and oxalic/sulfuric mixture acid with different concentrations, respectively, of which photoluminescence (PL) properties are studied under an excitation of 250 and 296 nm, respectively. The measurement shows that the AAO film samples prepared in oxalic acid and the mixture electrolyte, respectively, have the PL bands in the wavelength range of 250~550 nm. The sulfuric ions have a strong effect on the PL bands, and with increasing sulfuric ions content, the PL peak positions of the AAO film samples have a gradually blueshift, which is from 410 nm to 345 nm and 410 nm to 385 nm with excitation of 250 nm and 296 nm, respectively. However, the PL intensities of the AAO film samples increase with increa-sing sulfuric acid content under the excitation of 250 nm and decrease under the excitation of 296 nm. The PL of AAO films would originate from the centers transformed from the oxalic impurities with different existing or distributing forms in AAO films. The reasons for the experimental phenomena are discussed.关键词：optical films;porous anodic aluminum oxide;photoluminescence;blueshift;energy transfer117|97|0更新时间：2020-08-12
- 摘要：The solar irradiance monitor (SIM), a payload on the FY-3A satellite, is mainly used to monitor the change of solar irradiance. The SIM with wide angle of viewing field scans the sun every orbit. This kind design simplifies the system structure, but makes the on-orbit calibration more difficult. Based on the data obtained by SIM in more than one year, we study the factors that affect the calibration precision experimentally and theoretically, giving the equation and curve. First, by the ground-calibration experiment comparing with the World Radiometric Reference (WRR), we get the scale factors of the three radiometers, R1=1.0083, R2=1.0066 and R3=1.0065. Then, by the theoretical analysis of distance between sun and earth and the data curve of the solar irradiance measured, it is proved that the max solar irradiance is at perihelion (3 January) and the min solar irradiance is at aphelion(3 July), and the solar irradiance changes at the range of ±3.34% with the time variant. Using the astronomical formula and based on the correct time in the remote packages, gets the distance correction factor between sun and earth. It is obvious that the distance between sun and earth affects the calibration precision. In addition, analyzing the affection of the space background on the calibration precision and gets the calibration formula of the space irradiance. Furthermore, combining the characteristics of the wide field of view and the measurement method of step-scanning sun, the effects of the difference from incidence angle between just and over capturing sunlight on the solar irradiation measurement are mainly analysed, geting the the formula of the correction factor and curve with analysing the geometric parameters.Finally analyzing all of correction factors, the on-orbit calibration formula and curve are given.关键词：solar irradiance monitor;incidence angle;on-orbit calibration98|264|3更新时间：2020-08-12
- 摘要：Lasing from CO molecular is easy to realize about liquid nitrogen temperature, however, normally it is hard to lasing at room temperature. To solve this problem, experimental research on CO molecular lasing at room temperature is carried out with TEA technology, the results show that, at some limited conditions, there is no FO band lasing but just FB doing, The typical electric optical conversion efficiency is 1%; center wavelength at 5.3 μm; pulse energy 0.22 J; FWHM 700 ns and peak power 0.3 mW. When the pulse repetition rate is 500 Hz, 100 watts average power is obtained at room temperature.关键词：CO laser;room-temperature operating;fundamental band;first-overtone band110|88|0更新时间：2020-08-12
- 摘要：Sol-gels have been used to prepare Sr4Al14O25 ∶ Eu2+ , Dy3+ under low temperature at reducing atmosphere. The XRD shows that the production prepared at 1 200 ℃ is pure phase of Sr4Al14O25. Effects of some factors such as different Eu-to-Sr ratio and excitation wavelength were studied, the impact mechanism were also discussed. The obtained results indicate that: sintering temperature of sol-gel method is lower than that of high temperature solid-phase method. The excitation spectra were shifted to the long-wavelength, the 488 nm and 410 nm emission peaks were enhanced with an optimal molar ratio of 0.007 Eu2+.When the concentration is larger than 0.007, concentration quenching will occur.关键词：Sol-Gel;rare-earth;luminescence;long afterglow110|45|0更新时间：2020-08-12
- 摘要：In the classical mechanics frame, the particle motion equation in the periodic field is reduced to a pendulum equation, a possibility of the existence of a higher harmonic radiation is discussed by using Bessel function expansion of a generalized trigonometrical function, and the system basic characteristic in the fixing moment situation was discussed. Analytically going the equation solution and the period of vibration for the non-perturbed system by the Jacobian elliptic function and the first kind of elliptic integral, also analyzing the system phase plane characteristic and its stability with the numerical method.The result show that when the moment is zero, the system acceptance is maximum, the capture electronic number is the most, and the radiation intensity is the biggest. Increases along with the moment, acceptance reduces. When the value of dimensionless moment is 1, acceptance is the zero, the system is at the critical condition. Critical condition is related to system para-meter. Only obtaining the suitable adjustment parameter, it were hopeful to obtain higher harmonic radiation with the bigger intensity.关键词：nonrelativistic particle;higher harmonic radiation;pendulum equation;phase motion;Bessel function92|124|1更新时间：2020-08-12
- 摘要：The effects of the nonthermally distributed ions, the external magnetized field, and collisions on 3-D nonlinear dust acoustic solitary waves in inhomogeneous hot dusty plasmas have been investigated theoretically. A modified variable coefficients Korteweg-de Vries (MKdV) equation governing the 3-D nonlinear dust acoustic solitary waves have been derived by the reductive perturbation method. The approximate analytical solution of standard variable coefficients KdV equation derived from modified variable coefficients KdV equation has been obtained. This approximate analytical solution shows that nonthermal ions, inhomogeneity, collision, the oblique propagation of waves, the temperatures of dust and ions have effect on amplitude and width of 3-D nonlinear dust acoustic solitary waves. The amplitude of solitary waves is independent on the external magne-tized field, but the width of solitary waves is dependent on the external magnetized field. Moreover, The phase velocity of waves is dependent on nonthermal ions, the oblique propagation of waves, the temperatures of dust and inhomogeneity.关键词：inhomogeneity hot dusty plasmas;solitary waves;nonthermal ions;collision96|99|0更新时间：2020-08-12
- 摘要：SnO2 ∶ Eu3+ nanocrystals with different sizes in the ranges of 4 nm to 11 nm were prepared by hydrothermal method. X-ray diffraction (XRD) and photoluminescence (PL) measurements were used to characte-rize the sample. XRD showed that the samples structure kept pure rutile phase of SnO2. The excitation spectrum of the sample prepared without sintering only consisted of the intra shell f-f transitions of Eu3+ ions. The excitation spectra of the samples sintered at different temperature contained the intra shell f-f transitions of Eu3+ ions and the O2--Eu3+ charge transfer band. The emission intensities of the samples were closely related to the sizes of nanocrystals.关键词：SnO2 ∶ Eu3+;photoluminescence;hydrothermal106|69|3更新时间：2020-08-12
- 摘要：The luminescence properties of nanosized lanthanide oxide materials have attracted extensive interest because of their fundamental and technological importance. Gd2O3 has been widely used as host material due to abundant resource in nature. The emission of Sm3+ ions associated with the intra-4f-shell transition is very efficient and can be observed in the visible and near-infrared regions. Therefore, Sm3+ ion often plays a very important role in the luminescent processes of material. On the basis of studying on the luminescent properties of Gd2O3 ∶ Sm3+, we have made a comprehensive study on the effect of Na+ doping on the photoluminescent properties of nanocrystalline Gd2O3 ∶ Sm3+. Nanocrystalline Gd2O3 ∶ Sm3+ and Gd2O3 ∶ Sm3+ ,Na+ have been prepared by combustion synthesis using citric acid as the fuel and metal nitrates as oxidants. The structural, morphological and luminescent properties of the nanocrystals are also investigated. The results show that the samples obtained after annealing at 800 ℃ exist in cubic phase, and the grain size is approximately 30 nm. Photoluminescence properties were investigated for Gd2O3 ∶ Sm3+ and Gd2O3 ∶ Sm3+ , Na+ obtained at different annealing temperatures and different doping contents. The emission spectra of all samples present the characteristic narrow lines arising from the 4G5/2→6H<em>J transitions (J=5/2, 7/2, and 9/2) of Sm3+ ion under 275 nm excitation. The emission intensity of Sm3+ ion is enhanced with introducing Na+ ion into Gd2O3 ∶ Sm3+. The highest emission intensity is observed in Gd1.88Sm0.02Na0.10O3, whose intensity is 2 times than that of Gd2O3 ∶ Sm3+. The enhanced luminescence by Na+ doping is mainly regarded as the results of the flux effect of Na+ and the creation of oxygen vacancy by Na+ ion doping. The Na+ codoping results in the better crystallization and larger grain size, furthermore reduced the luminescence quenching by the surface defects. This fact causes an increase in the luminescent intensity. The oxygen vacancy is resulted from the occupation of Gd3+ site by Na+ ion, acting as sensitizer for the effective energy transfer, resulting in the improvement of luminescent intensity. A lot of defects can be induced in the system with a gradual increase of Na+ content. They act as non-radiative transition channels and thus lead to the luminescence quenching.关键词：Na+;Gd2O3 ∶ Sm3+ nanocrystals;enhanced photoluminescence99|147|5更新时间：2020-08-12
- 摘要：The phosphor Ca2Zn4Ti16O38 ∶ Pr3+ , Na+ has received increasing interest owing to its high chemical stability, broad red emission and special long afterglow properties. However, the sintering temperature for obtaining pure Ca2Zn4Ti16O38 ∶ Pr3+ , Na+ is confirmed to be 950 ℃ and the sintering period is 21 h for sol-gel synthesis of this phosphor. So, optimization of synthesis conditions of Ca2Zn4Ti16O38 must be carried out.It is most important to get uniform and transparent gel in the sol-gel process. The results show that the mixture solution is clarification when pH ≤ 3 (adjusted by HNO3 solution).While increasing the pH value (adjusted by ammonia solution) the mixture solution begin to come forth muddy. After dried in 150 ℃, the exrogel shows yellow color under pH ≤ 3 and others present black. After further heated at 400 ℃ for 2 h, a dark dry gel is obtained and ground in an agate mortar to black powder serving as the precursor for the present work. The final phosphor powder is obtained after reheated at 900 ℃ for 8 h. Crystalline phases, morphology and photoluminescence properties have been characterized by using powder X-ray diffractometry (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer, respectively. XRD patterns show that the synthesized Ca2Zn4Ti16O38 powders possess well structure when pH ≤3. Extra-resultants such as CaTiO3, Zn2TiO4 and TiO2 appeared when pH ≥ 5.The SEM results showed that the samples obtained at pH ≤ 3 are fleecy and uniform. With the increasing pH value, particles gradually become larger, the reunion and sinter phenomenon become seriousevident.TG-DAT curves reveal the different various trends for the precursors of pH=3 and pH=9. The electrical alkoxy-OR of Ti (OC4H9)4 make metal ions Ti4+ highly vulnerable by nucleophilic attack. Ti (OC4H9)4 easily hydrolyzes or polymerizes no matter what in acid or alkaline conditions. When pH≤3, H+ speeds up the hydrolysis of Ti (OC4H9)4 and to replace the form of coordination of tetrabutyl titanate alkoxy, direct bonding with titanium ion formed by hydrolysis of Ti (OH) <em>x(AC)<em>y(with x+y=4). However, when pH=9, a large number of OH- ions exists in Ti (OC4H9)4 hydrolysis and produces Ti(OH)4 or TiO(OH)2, and that the other cations Ca2+, Zn2+ and Pr3+ from Ca(OH)2, Zn(OH)2 and Pr(OH)3 will not mixe with each other effectively and will not form other phases. Thereby, keeping the pH ≤ 3 is necessary for cations to uniformly mix to inhibit Ti (OC4H9) directly hydrolyzed to form Ti (OH)4 precipitation. Excitation and emission spectra indicate that the phosphors exhibit the highest excitation bands in the visible region in the ranges of 450~495 nm originated from 4f→4f transition, as well as red emitting of Pr3+ at 613 nm(1D2→3H4)and 644 nm (3P0→3F2) when pH≤3, which result in, upon excitation with 475 nm, the red emission at 644 nm decays slower than that of pH ≥ 5. This fact suggests that Ca2Zn4Ti16O38 ∶ Pr3+, Na+ obtained via acid sol-gel process (pH ≤ 3) gives the good red long afterglow under visible light irradiation.关键词：Ca2Zn4Ti16O38 ∶ Pr3+;sol-gel method;pH value;red phosphor;long afterglow111|60|3更新时间：2020-08-12
- 摘要：SrZnP2O7 ∶ Tb3+, SrZnP2O7 ∶ Ce3+ and SrZnP2O7 ∶ Ce3+,Tb3+ phosphors were prepared by solid state reaction, and their luminescent characteristics were investigated. SrCO3(A.R.), ZnO(A.R.), NH4H2PO4(A.R.), Li2CO3(A.R.), Na2CO3(A.R.), K2CO3(A.R.), NH4Cl(A.R.), Tb4O7(99.99%) and CeO2(99.99%) were used as starting materials, after these individual materials ground thoroughly in an agate mortar, the homogeneous mixture was heated at 900 ℃ for 3 h in reduce atmosphere, and these phosphors were obtained. The phase presents of the samples were characterized by powder X-ray diffraction (XRD) (D/max-rA, Cu Kα, 40 kV, 40 mA, λ=0.154 06 nm). The excitation and emission spectra of these phosphors were measured by a SHIMADZU RF-540 fluorescence spectrophotometer. SrZnP2O7 ∶ Ce3+ shows a broad band at 329 nm. SrZnP2O7 ∶ Tb3+ has six emission peaks at 420, 443, 491, 545, 587 and 625 nm which correspond to the 5D3→7F5, 5D3→7F4, 5D4→7F6, 5D4→7F5, 5D4→7F4 and 5D4→7F3 characteristic transitions of Tb3+ , respectively, at 380 nm excitation. Monitoring 545 nm peak, the excitation spectrum extends from 200 nm to 400 nm, and the peak locates at 380 nm. Energy transfer from Ce3+ to Tb3+ in SrZnP2O7 ∶ Ce3+,Tb3+ phosphor was investigated, and the emission intensity of SrZnP2O7 ∶ Tb3+ can be enhanced by energy transfer from Ce3+ to Tb3+. Under the conditions of charge compensator Li+, Na+, K+ or Cl- incorporated in SrZnP2O7 ∶ Tb3+ phosphor, the emission intensities of the phosphor are enhanced, too.关键词：luminescence;SrZnP2O7;Ce3+;Tb3+;energy transfer96|55|5更新时间：2020-08-12
- 摘要：CaBa2(BO3)2 ∶ Tb3+ green phosphor was synthesized by the general high temperature solid-state reaction and its luminescence properties were investigated. It shows four major emission peaks locating at 496, 549, 588 and 622 nm, corresponding to the 5D4 →7F6, 5D4 →7F5, 5D4 →7F4 and 5D4 →7F3 typical transition of Tb3+ , respectively. The most intense peaks located at 496 nm and 549 nm,the phosphor shows excellent green emission.The excitation spectra contains a abroad band extending from 200 nm to 300 nm, which correspond to 4f7-5d1 broadband absorption. The effects of doped Tb3+ concentration and charge compensating of Li+, Na+ and K+ on the emission intensity were also investigated: the concentration quench phenomenon does not appear nearly and Li+ gives the best improvement to enhance the intensity of the emission.Make sure the best mixture ratio of raw material which are CaCO3,BaCO3,H3BO3. Emission intensity of synthetic crystal is the best, when H3BO3 is excessive to 3%.关键词：luminescence;phosphor;CaBa2(BO3)2 ∶ Tb3+120|107|0更新时间：2020-08-12
- 摘要：There exists an increasing demand for red emitting phosphors to be used in color display and illumination. SrAl12O19 ∶ Eu2+ has attracted much attention for its excellent properties such as high quantum efficiency and good stability. However, the emission of SrAl12O19 ∶ Eu2+ peaks at 400 nm, which is hard to be used in display and illumination. As we know, Cr3+ with red emission lines is one of the most used activators for solid state laser and other luminescent materials. Therefore, we have studied the emission and excitation spectra as well as energy transfer in SrAl12O19 ∶ Eu2+ , Cr3+ . The Cr3+ , Eu2+ singly doped and co-doped samples were synthesized by solid-state reaction at 1 400 ℃. The emission band of Eu2+ peaked at 400 nm is originating from the 5d-4f transition, which has large spectral overlaps with the 4A2→4T1 absorption band of Cr3+ covering between 350 nm and 450 nm in the ultraviolet-blue region. It means the possibility of energy transfer from Eu2+ to Cr3+. The conversion of violet-blue emission to the red may be obtained by the energy transfer. In the co-doped samples, the emission band of Eu2+ appears in the range of excitation spectra of Cr3+ emission, which indicates the occurrence of energy transfer from Eu2+ to Cr3+. In order to explain energy transfer further, the lifetime of Eu2+ emission in SrAl12O19 ∶ 1%Eu2+ , x%Cr3+ (x=0, 0.2, 1.0, 2.0, 3.0, 4.0, 5.0) has been measured. It shows that the lifetime of Eu2+ reduces following increasing Cr3+ concentration due to the energy transfer from Eu2+ to Cr3+. The energy transfer efficiency as a function of Cr3+ concentration has been calculated using the measured fluorescent lifetimes of Eu2+ , indicating the transfer efficiency increases with increasing Cr3+ concentration, and may reach 50% as Cr3+ concentration is 0.05.关键词：red phosphor;energy transfer;Eu2+;Cr3+143|175|0更新时间：2020-08-12
- 摘要：The Sr3Al2O6-3x/2Nx ∶ Eu2+ phosphor was synthesized by solid-state reaction method. The study of Sr3Al2O6-3x/2Nx ∶ Eu2+ spectra indicated that the emission spectra was the broad band spectra peaking at 600 nm when exciting at 400~550 nm. The XRD results showed that the crystal structure of Sr3Al2O6-3x/2Nx ∶ Eu2+ was the same as Sr3Al2O6. Effect of Eu2+ concentration on luminescent intensity of Sr3Al2O6-3x/2Nx ∶ Eu2+ phosphor was investigated. The results showed that the luminescent intensity firstly increased with increasing Eu2+ content and then decreases. The Eu2+ content corresponding to the maximal luminescent intensity is 15%. According to Dexter theory, the concentration quenching mechanisms are the q-q (quadrupole-quadrupole) interaction. The emission intensity of Sr3Al2O6-3x/2Nx ∶ Eu2+,Ce3+ is higher than that of the other phosphor activated by Eu2+ only.关键词：luminescence;Sr3Al2O6-3x/2Nx;phosphor;europium107|165|1更新时间：2020-08-12
- 摘要：The β-NaGd0.794Yb0.200Ho0.001Tm0.005F4 nanoparticles were synthesized by a hydrothermal method. The studies of the powder X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy show that the β-NaGd0.794Yb0.200Ho0.001Tm0.005F4 nanoparticles crystallize in the shape of hexagonal morphology and ellipsoidal sphere with an average size of about 23 nm. Room-temperature bright white light emission in Yb3+, Tm3+, Ho3+ ions doped β-NaGdF4 nanoparticles was observed in an upconversion process under the excitation of single-wavelength diode laser of 980 nm. The white light consists of the blue, green, and red upconversion emissions, which correspond to the transitions 1G4 → 3H6 of Tm3+, 5F4 →5I8 and 5F5 → 5I8 of Ho3+ ions, respectively. By the spectral positions at 476, 542, and 650 nm we have the white-light coordinates x=0.271 7 and y=0.267 3.111|21|2更新时间：2020-08-12
- 摘要：One-dimensional silicon carbide-carbon nanotube composite nanostructure was fabricated using a direct solid reaction process between pure silicon powders and carbon nanotubes at 1 400 ℃ in this paper. A structural and optical analysis, by mean of X-ray diffraction, scanning electron microscopy, Raman scattering and cathodoluminescence spectroscopy were performed. The outer diameter of the as-prepared one-dimensional composite nanostructure was approximately 60 nm. The composite products showed pronounced luminescent properties with three emission bands centered at 2.89, 2.39 and 2.22 eV by room temperature cathodoluminescence.关键词：SiC;composite nanostructure;cathodoluminescence;carbon nanotube104|187|0更新时间：2020-08-12
- 摘要：Light source is a very significant lighting component, and plays a crucial role in the optical measuring process for wave slope field on sea surface. Rational selection of light source is one of the important factors for ensuring accuracy and layout of the system. Based on the advantages compared with short-arc xenon lamp as lighting in luminous efficiency, durability, reliability, safety and consuming power, LEDs are becoming the preferred candidate for many lighting applications that require uniform illumination distribution. An assumption that applied LEDs as light sources of the measuring device is presented, the feasibility has clarified by theoretical calculation and optical software simulation.关键词：light sources;LED modeling;LED arrays;illumination uniformity103|111|1更新时间：2020-08-12
- 摘要：Inverted heterojunction organic solar cells with a structure of ITO/BCP or Alq3(x=0,2,6,10,20,40 nm)/C60(50 nm)/Rubrene(50 nm)/MoO3(5 nm)/Al(130 nm) were prepared, in which BCP or Alq3 was used as electron transport layer. The experiment results show that when BCP or Alq3 ≤ 6 nm, device performance hardly changes with the increase of thickness of electron transport layers; When BCP or Alq3 ≥ 10 nm, device performance degrades quickly with the increase of thickness of Alq3, but slower and open circuit voltage remains unchanged with the increase of thickness of BCP. When electron transport layer is thin, the roughness of ITO makes electrons injection from C60 into ITO easy; when electron transport layer is thick, since band bending of BCP/C60 almost make that potential barrier between BCP and C60 does not exist, the bad device performance with BCP mainly comes from poor BCP electron mobility, that of one with Alq3 was primarily due to potential barrier between Alq3 and C60.关键词：organic solar cells;inverted;band bending;C60110|212|0更新时间：2020-08-12
- 摘要：Six scatters is increased in two-dimensional triangular photonic crystal ring resonator, forming a new ring-cavity structure, so that the transmission of light waves attain 90%, the bandwidth is relatively small in the optimized ring resonators. By changing the refractive index of photonic crystals dielectric cylinders, but also the selection of ring cavity wavelength is changed, so discriminate clearly two different wavelength, the wavelength of partial wave is the range of the communication wavelength. Different refractive materials of photonic crystals connected together to form a new kind of photonic crystal WDM, compared with the same kinds of material, which has the advantages of high efficiency and multi-wavelength selection. This heterogeneous structure can be used to build a multi-wavelengths structure, it is also the foundation for the facture of multi-channels WDM device.关键词：photonic crystal;ring resonator;WDM;scatters;refractive index113|249|1更新时间：2020-08-12
- 摘要：CeO2 films were deposited on p type Si wafers by e-beam evaporation technology. Three photoluminescence peaks which located around 385, 418 nm and 445 nm were obtained after annealing in weak redu-cing atmosphere at high temperature. It was indicated that CeO2 films transferred to amorphous state as the valence conversion of Ce4+→Ce3+, which was induced by reducing atmosphere annealing. The PL spectrum of 385 nm and 418 nm was assigned to the transition from 5d energy level of Ce3+ ions to 2F7/2 and 2F5/2 manifolds of 4f energy level, respectively, while the peak around 445 nm was assigned to the O vacancies of SiO2. Furthermore, the changes of PL intensity in CeO2 films annealed with different temperature and time were also investigated. The maximum PL intensity was obtained after the films annealing at 1 200 ℃ for 2 h compared with other temperature and time. It was indicated that valence conversion of Ce4+→Ce3+ was enhanced by increasing annealing temperature and time, that is, the PL intensity of the films was also enhanced because of the increasing of Ce3+ ions, however, the energy transfer between Ce3+ and Ce3+ ions, occurred as excessive Ce3+ ions were formed in the films, resulting in concentration quenching.关键词：CeO2;photoluminescence;energy transfer117|140|0更新时间：2020-08-12
paper
- 摘要：Self-catalyzed InP nanowires were grown on Si (100) and Si (111) substrates by metal-organic chemical vapor deposition. Morphology, crystal structure, and optical properties of the nanowires were investigated. Using scanning electron microscope (SEM), we found that the morphology of the InP nanowires grown on Si (100) was similar with that of the InP nanowires grown on Si (111). The only difference between them was the density of the nanowires. Most nanowires are long and straight; the angles between the nanowires and the Si substrate are diverse. This was attributed to the native oxide on Si substrates. The X-ray diffraction results showed that two peaks of InP (111) and InP (220) was able to be seen in the spectra. Two more peaks of InP (200) and InP (311) were observed if we continue to supply PH3 for 15 min after the nanowires growth for 7 min. The InP (220), InP (311), and InP (200) originated from InP crystal on the tip of the nanowires. Only the InP (111) originated from the InP nanowires. The transmission electron microscope (TEM) and transmission electron diffraction (TED) results showed that the nanowires exhibit zinc-blende (ZB) crystal structure; the main growth direction of the nanowires was 〈111〉; the nanowire has twin stacking faults. Temperature-dependent photoluminescence (PL) spectra of Fe doped InP substrate and InP nanowires grown on Si (100) were measured in the rages of 80 to 300 K. The PL peak at 1.425 eV for 80 K,for InP nanowires, shifted to 1.379 eV at 300 K, while the PL peak energy of InP substrate was 1.413 eV and 1.349 eV, respectively. The reasons for the blue-shift of the nanowires could be the existence of twin stacking faults. Due to laser-induced heating, the TO and LO phonon peaks of the nanowires revealed downshift and asymme-tric broadening compared with those of bulk InP at room temperature.98|215|1更新时间：2020-08-12
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