最新刊期
卷 39 ， 期 2 ， 2018
- 摘要：The photo-instability and degradation of colloidal quantum dots (QDs) are major challenges in their applications. We report photo-stability enhancement of colloidal CdSe/ZnS QDs passivated in SiO2 thin film deposited by RF magnetron sputtering. First, the red (615 nm emission) CdSe/ZnS QDs were synthesized by tri-n-octylphosphine assisted successive ionic layer adsorption and reaction method. The QDs were then spin-coated to the SiO2/Si substrate, and a SiO2 film with a thickness of 20 nm was deposited on the QDs as a passivation layer by magnetron sputtering. The photoluminescence spectra of passivated and un-passivated QDs were investigated by using a continuous wave laser source, which was irradiated in air and vacuum respectively. The results show that the PL intensity of the QDs without SiO2 passivation decreases significantly, and the PL peak shifts to blue and the FWHM increases continuously with the increasing of the irradiation time. Comparative analysis shows that SiO2 film can prevent the oxidation of QD surface from water vapor and oxygen molecules and thus the stability of CdSe/ZnS QDs is significantly improved.关键词：photoluminescence;quantum dots;CdSe/ZnS;photo-stability;SiO2 passivation174|58|1更新时间：2020-08-12
- 摘要：Tb3+ doped high density germanate glasses were prepared by melt-quenching method. Their physical and luminescent properties were characterized by transmittance spectra, density, photoluminescence, fluorescence lifetimes and X-ray excited luminescence spectra. The transmittance spectra show the glasses have good transmittance in the visible spectrum region. The high Lu2O3 and Gd2O3 contents ensure germanate glass density approach to 6.4 g/cm3. The glasses show intense green emissions under 377 nm light and X-ray excitations. The lifetimes of 544 nm emission are in the range from 1.325 ms to 1.836 ms. The results indicate that Tb3+ doped high density germanate glass is a scintillating material candidate used in X-ray detector for slow event.关键词：high density;Tb3+;scintillating glasses;luminescence properties158|64|5更新时间：2020-08-12
- 摘要：A series of Eu3+ doped K2CaP2O7 phosphors were prepared by high temperature solid state reaction method. The phase structure, morphology, luminescence properties of the phosphors were investigated by XRD, SEM, luminescence spectra and luminescence decay curves. The results show that all the phosphors have monoclinic structure, the doping of Eu3+ ions does not significantly influence the structure of K2CaP2O7 host lattice. The phosphors exhibit irregular morphology with the particle size of several microns. Under 393 nm excitation, Eu3+ doped K2CaP2O7 samples emit red lights with the most intense peak at 613 nm. The optimal doping concentration of Eu3+ is 0.08 in the host, the critical energy transfer distance between Eu3+ ions is calculated to be 1.61 nm. The doping concentration has little influence on the decay time of Eu3+, the decay times of all the samples are in the 2.45-2.58 ms range. Moreover, the relative emission intensity maintains 73% of its original intensity when the temperature reaches 150℃. All the above results indicate that Eu3+ doped K2CaP2O7 may be a potential red phosphor.关键词：red phosphor;Eu3+;K2CaP2O7156|70|1更新时间：2020-08-12
- 摘要：CaTiO3:Re3+(Re=Eu, Dy) phosphors were synthesized by hydrothermal method. XRD, SEM and PL spectra were used to characterize the samples. The crystallinity and luminescent properties of CaTiO3:Re3+ phosphors reach optimal state when pH=12, and SEM analysis indicates that the powder has good dispersion when the particle size is about 450 nm. The optimum concentration of rare earth ions is determined. The emission peaks of CaTiO3:0.12Dy3+ locate at 485 nm (blue) and 576 nm (yellow) under 353 nm excitation. The intensity ratio of the blue-yellow emission peaks (IY/IB) produced by the two transitions can be regulated via adjusting Dy3+ concentration. Therefore, luminescent color of CaTiO3:Dy3+ phosphor can be tuned by changing Dy3+ concentration.关键词：CaTiO3;hydrothermal method;luminescence;pH162|52|0更新时间：2020-08-12
- 摘要：Pyromellitic diimide(PMD) nanomaterial was prepared by vacuum vapor deposition and molecular self-assembly method using PMD as raw material. A new method for determination of trinitromethane was established by fluorescence chemical sensor. The properties of PMD nanomaterials synthesized by vacuum vapor deposition method were characterized by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, UV spectroscopy, differential thermal analysis and fluorescence spectroscopy. The scanning electron microscopy (SEM) results show that the PMD nanomaterial has a banding network with a length of 30-100 μm. TEM images show that the PMD nanobelts have a width of 100-300 nm, and the nanowires have a diameter of 120-220 nm. The main driving force for constructing the nanostructures of PMD in the self-assembly process is from the intermolecular hydrogen bonds and π-π weak interaction. The experiments show that some of the lower boiling organic molecules have a strong effect on the fluorescence quenching of PMD nanomaterials, especially trinitromethane does a sensitive response to PMD nanostructures. The linear range of trinitromethane is from 2.19×10-5 to 1.37×10-4 mol/L(R2=0.995) with the detection limit of 1.02×10-6 mol/L.关键词：pyromellitic diimide;vacuum vapor deposition method;molecular self-assemble;nanochemical sensor;trinitromethane126|103|0更新时间：2020-08-12
- 摘要：The phase transition properties of VO2 thin films irradiated by nanosecond laser were researched using the pump-probe method. At first, VO2 thin films were successfully deposited by DC magnetron sputtering method, and the samples were identified as high quality thin films by analysis of (X-ray diffraction)XRD and (Atomic force microscope)AFM. Then, the transmittance of vanadium oxide thin films at the wavelength of 532 nm with temperature change was measured. It is found that the transmittance increases from 32% to 37% with the temperature going up, which is completely opposite to the situation in infrared band. On this basis, we chose 1 064 nm pump laser and 532 nm probe laser to research the effect of nanosecond laser parameters, energy density and repeat frequency, on the phase transition properties of VO2. In addition, the ANSYS software is also used to analyze the per pulse heating range of VO2 thin films under nanosecond laser. The results suggest that the per pulse heating can reach the phase transition temperature of VO2 when the nanosecond laser energy density is more than 30 mJ/cm2. The response time increases slightly with the increase of the nanosecond laser energy density, and the minimum response time is around 14 ns. The repetition frequency of nanosecond laser within 100 Hz has no obvious effect on the phase transition response of VO2 thin films. The recovery time varies with nanosecond laser energy according to natural exponential law, and it correlates closely with substrate material and nanosecond laser parameters. We can improve the laser protection effect by optimizing the substrate material parameters of VO2 thin film.关键词：vanadium dioxide thin films;pump-probe;nanosecond laser;532 nm laser;phase change response time;phase recovery time117|65|3更新时间：2020-08-12
- 摘要：In order to obtain the low cost and high crystalline thin films, the properties of rubrene films were investigated with Polyvinyl Pyrrolidone (PVP) as interface modification layer on the Si/SiO2 substrate by solution process. First, PVP films were spin-coated on Si/SiO2 substrate. The surface morphology and roughness (RMS) of PVP layer were analyzed by polarizing optical microscope (POM) and atomic force microscopy (AFM). Then, rubrene films were drop-coated on the PVP layer and dried out. The effects of PVP layer with the different PVP concentration and film-forming temperature on rubrene morphology were studied. The crystal structures of PVP films and rubrene films were carried out by X-ray diffraction. Finally, growth mechanism mode of rubrene films on the PVP interface modification layer was proposed. The results indicate that the temperature of 80-140℃ and lower concentration of PVP are apt to prepare spherulites with high crystallinity, and the crystals size becomes larger when the temperature increases. PVP used as interface modification layer is beneficial to improve film-forming property of rubrene and prepare crystalline films with high crystallinity.关键词：solution process;Polyvinyl Pyrrolidone(PVP);interface modification;rubrene crystals;crystal morphology143|60|0更新时间：2020-08-12
- 摘要：Green top emitting OLEDs were fabricated by using green CdSSe/ZnS quantum dots with core-shell structure. The photoelectric properties of the devices were studied in detail. Compared to the bottom emitting device with the similar structure, the top emitting device was significantly improved in brightness, efficiency, color purity, and voltage stability of the spectrum. Under the same voltage of 7 V, although the bottom emitting device has greater current density, the brightness is only 831 cd/m2, while the brightness of the top emitting device can reach 1 350 cd/m2, and the highest brightness can reach 7 112 cd/m2. In efficiency, the maximum current efficiency of the top emitting device can reach 6.54 cd/A, which is far greater than 1.89 cd/A of the bottom emitting device. In terms of spectrum, the red and blue parts of the bottom emitting devices are completely suppressed in the top emitting devices, and the half height width of the top emission spectrum is significantly narrowed with higher color purity. When the voltage varies from 4 V to 9 V, the spectrum of the top emitting device remains stable, and the color coordinates move only (-0.005,-0.001). The results show that the top emission structure is beneficial to improve the luminance, efficiency, color purity and voltage stability of the quantum dots.关键词：quantum dots;light-emitting device;top-emitting;green emission143|83|3更新时间：2020-08-12
- 摘要：Multi-color laser diode array end-pumped Nd:YAG electro-optical Q-switched laser without temperature controlled was developed. Using a 4 000 W multi-color QCW laser diode array as the pumping source, and fast axis collimator, lens duct as coupling system, and RTP as Q-switch, end-pumped φ6 mm×60 mm Nd:YAG crystal, the laser obtained a 1 064 nm pulsed laser output with maximum output energy of 74.4 mJ, pulse width of 15 ns and optical conversion efficiency of 11% at the repetition rate of 5 Hz and 25℃. The spectral characteristics of multi-wavelength LDA and the output characteristics of the laser were tested under operating temperature of 25℃ to 55℃, the output energy of the laser rapidly decreases, then gradually stabilizes with the increase of the working temperature. When the repetition rates are 5 Hz and 10 Hz, the minimum output energy of the laser is 48 mJ and 37 mJ, respectively. Experiments indicate that the multi-color laser diode array has more value in realizing no temperature control of high energy all-solid-state lasers.关键词：all-solid-state-laser;multi-color laser diode array;lens duct;electro-optical Q-switched;high energy196|130|6更新时间：2020-08-12
- 摘要：The electro-static discharge (ESD) performance of the organic light emitting diodes was investigated experimentally at the human body model equivalent pulses by utilizing the transmission line pulsing (TLP) tester. ESD with 200, 800, 1 600 V was applied on four groups OLEDs. The electrical and optical characteristics of OLEDs were analyzed before and after ESD stress. The lifetime tests were carried out for the fresh samples and the devices undergoing ESD stresses. The experiment results show that the electro-luminescence spectra of OLEDs are insensitive to ESD. Because of the short term inhibition effect of ESD on the carriers, the luminance of OLEDs decreases slightly with the increasing of the strike voltage. When the strike voltages are 200 and 800 V, I-V characteristics of OLEDs don't change. When the strike voltage is 1 600 V, the leakage current increases obviously. The accelerated life test results show that ESD has no obvious regular influence on the life of OLEDs, but it will increase the probability of non essential aging failure to a certain extent.关键词：organic light emitting diode(OLED);electro-static discharge(ESD);lifetime150|72|2更新时间：2020-08-12
- 摘要：The use of 1-Octadecanethiol(ODT,CH3[CH2]17SH) to prepare clean GaAs(100) surface with low surface state intensity was demonstrated. Firstly, the X-ray photoelectric spectroscopy (XPS) of GaAs(100) passivated by 1-Octadecanethiol and Thioacetamide(TAM,CH3CSNH2) was compared. Secondly, the ODT passivation time at room temperature condition was optimized by photoluminescence intensity (PL) method. Lastly, the surface morphology before and after passivation using scanning electron microscope (SEM) was discussed. Experimental results indicate that the GaAs(100) passivation using 1-octadecanethiol is shown to lead a lower oxide contamination and a higher sulfide thickness compared with the traditional passivation method of TAM. In the range of 0-24 h, the room-temperature photoluminescence intensity keeps a continuous enhancement with time extend, and the maximum enhancement is 116% than un-passivation one; SEM shows that GaAs(100) wafer has good surface morphology after ODT passivation. This indicates that the surface passivation of GaAs(100) using 1-octadecanethiol is effective.关键词：passivation;GaAs;1-Octadecanethiol173|86|1更新时间：2020-08-12
- 摘要：We performed failure mode analysis (FMA) on the suddenly failed high-power 975 nm strained quantum well diode lasers. At first, we believed that the lasers suffered catastrophic optical damage (COD) at the mirror facets, which is called COMD. However, by electroluminescence (EL), we found that some lasers suffered COD only in the bulk without any damage at both facets, which is called COBD, thus guiding our further improvement. Among all the 90 lasers that suffered COD, the EL images demonstrate that the dark line defects (DLDs) can originate from the facets or the bulk. These DLDs are highly non-radiative region and usually confined in the active region with several branches, which leads to the dramatic decrease of the optical power. And to the different COD modes, the common features of DLDs were interpreted and compared in detail. Furthermore, the causes to the two typical COD modes were analyzed, and suggestions were made to suppress the COD process and further improve the high-power laser diodes.关键词：high-power diode lasers;failure mode analysis;electroluminescence;catastrophic optical damage;dark line defect279|113|0更新时间：2020-08-12
- 摘要：In order to optimize the performance of nanolasers, a nanolaser structure based on a nanowire/semicircle MgF2/triangle air slot and metal ridge was proposed. The models produce that the SPP mode and nanowire waveguides coupled in the dielectric layer of low refractive index can store light energy like a capacitor under low refractive index clearance. Low refractive index of the air tank field strength increased significantly. The electric field distribution, the modal properties, the quality factor and the lasing threshold are investigated by using the finite-element method on the basis of the COMSOL Multiphysics platform. Through the comprehensive analysis of each part of the line chart, the model performance data are obtained. Simulation results reveal that this kind of nano laser has a low propagation loss and high field confinement ability, its minimum normalized mode area is only 0.004 8, the minimum propagation loss is only 0.002. The waveguide mode field area and limiting factors show that the modeled laser can achieve sub-wavelength constraints of the output light field. It can achieve low gain threshold, low transmission loss and high quality factor requirements.关键词：nanolaser;surface plasmon;mode properties;threshold;quality factor;finite element124|298|0更新时间：2020-08-12
- 摘要：In order to output light beam of higher power and higher brightness, the fiber coupled diode laser module consisting 16 single emitter semiconductor laser diodes with 12 W was designed by ZEMAX. This module can produce 189.4 W from a standard optical fiber with core diameter of 100 μm and numerical aperture of 0.22. The coupling efficiency is 98.6% and the brightness is above 94.66 MW/cm2-str. The new heat sink structure was designed by using SolidWorks software and the thermal analysis was simulated by ANSYS software. The results show that the hightest temperature of new heat sink structure is 42.4℃, 1℃ lower than before.关键词：ZEMAX;high brightness;coupling;temperature;ANSYS133|100|2更新时间：2020-08-12
- 摘要：The effect of carrier recombination mechanism on modulation bandwidth of InGaN MQWs LED was investigated with varying MQWs structures. LED with narrow well has a faster modulation speed because of high radiative recombination rate and carrier leakage. LED sample using InGaN barrier with 1% In content has a higher modulation bandwidth than LED with GaN barrier for the reason of higher radiative recombination rate. While in the case of 5% In content, carrier leakage dominates all the recombination mechanisms and crystal defect related SRH and Auger recombination are also severe. In addition, the rate of SRH and Auger recombination is very high, which leads to fast modulation speed.关键词：light emitting diode (LED);visible light communication;modulation bandwidth;carrier lifetime;recombination mechanism199|77|2更新时间：2020-08-12
- 摘要：The effects of barrier layer thickness on the electroluminescence performance of InGaN/GaN multiple quantum wells(MQWs) were investigated, and the relevant physical mechanisms were discussed. It is found that the electroluminescence (EL) intensity of the samples which have thicker barrier layers is stronger under the same injection current condition, and their increase with the increase of injection current is more rapid. According to the analysis, a proper increase of barrier layer thickness can not only widen the potential barriers, but also increase the tilt of the energy band of MQWs due to the polarization effect and the localization potential due to in In-rich clusters, thus reducing the electron current leakage and increasing the carrier confinement ability, thereby improving the luminescence performance of the InGaN/GaN multiple quantum wells.关键词：InGaN/GaN;multiple quantum wells;barrier thickness;electroluminescence151|83|0更新时间：2020-08-12
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Fabrication of Zirconia Dielectric Layer by Spin Coating and Its Application in Thin Film Transistor
摘要：The zirconia dielectric film was prepared by spin coating, and the effect of spin coating speed and annealing temperature on the properties of the film was discussed. The post-high temperature annealing, on the one hand, can cause the zirconia hydrate to dehydrate to form zirconia, and on the other hand, crystallize the zirconia film. In addition, when the speed is high enough, the change has no significant effect on the thickness and roughness of the film. When the spin coating speed is 5 000 r/min and the annealing temperature is 300℃, the prepared insulating layer has good thickness uniformity, with a roughness of 0.7 nm, and the leakage current density is 3.13×10-5 A/cm2 at electric fields of 1 MV/cm. Thin film transistor (IGZO-TFT) was prepared on a glass substrate using ZrO2 thin film as gate insulating layer. The mobility is 6.5 cm2/(V·s) and the on-to-off current ratio is 2×104.关键词：zirconia film;solution process;spin coating speed;annealing temperature200|100|3更新时间：2020-08-12 - 摘要：The pest trapping system based on narrow and single LED light source spectrum was designed. The optimal spectrum of LED light source was selected and determined to realize the maximum amount of the insect trapping through the pest phototaxis adaptive mode combining the function of the system, such as the detection of environmental parameters, detection of the insect trapping, single lamp multi band LED control, and network distributed layout. The structure of network trapping system adapted to different plant height and density in the field of ecological agriculture was designed. The lamp with multi band LED was designed based on the pest phototaxis and chromaticity. The stability of single spectrum band and the effect of multi-band were analysized by testing the LED lamp from 365 to 430 nm.关键词：LED lighting;self-adaption;trapping system;phototaxis141|80|0更新时间：2020-08-12
- 摘要：Aimed at the limited bandwidth of LED devices used in a visible light communication (VLC) system, a bandwidth efficiency spatial modulation scheme based on multi-dimensional carrierless amplitude and phase named OSM-CAP was proposed in this paper. The bit sequence was divided for two parts in OSM-CAP system, a part was modulated to represent the spatial information and then used to select the active LED, another part convolved with multi-dimensional CAP filter banks acquired by solving a quadratic programming algorithm, and then some modifications were performed to obtain unipolar signal in OSM-CAP VLC system because only real and positive signals could be intensity modulated. According to Lambertian reflection model and considering light of sight link corrupted by additive white Gaussian noise, the theoretical bit error rate (BER) of OSM-DCO/CAP and OSM-U/CAP was derived and corroborated by Monte Carlo simulations. Meanwhile, the effects of the dimensionality of CAP filter banks and the channel parameters on the system performance were evaluated in the room in size of 5 m×5 m×3 m. The numerical results show that the higher dimension of filter banks, the better error performance of OSM-CAP VLC system. In addition, increasing the number of the receiver, enlarging the separation distance between two LEDs, decreasing the distance between the transmitter and receiver, and using something to block the transmission link, can improve the system reliability.关键词：visible light communication(VLC);multi-dimensional carrierless amplitude and phase modulation;spatial modulation;Lambertian reflection module;bit error rate(BER)131|96|2更新时间：2020-08-12
- 摘要：The interaction of cefetamet pivoxil (CFP) and pepsin (PEP) has been investigated by fluorescence spectra, synchronous fluorescence spectra, UV-Vis absorption spectra, circular dichroism (CD) spectra and molecular docking method at 298, 303 and 310 K. The results indicate that CFP mainly uses the static quenching method of nonradiative energy transfer to cause the fluorescence quenching of PEP, which is mainly combined by static electricity forces. The binding rate is 74.73%-92.13% at 310 K. The effect of CFP on PEP structure was studied by synchronous and circular dichroism (CD). The results show that the binding of CFP and PEP induces the conformational change of PEP, and quenches the endogenous fluorescence in PEP. The results of molecular docking reveal that CFP locates in the catalytic active site of PEP, and the results of docking are consistent with that of experimental calculation. It is confirmed that the addition of CFP leads to the gradual quenching of PEP fluorescence. The fluorescence quenching reaction of CFP to PEP can be used to determine the content of CFP in the medicine.关键词：cefetamet pivoxil;pepsin;interaction;molecular docking;spectroscopy144|86|1更新时间：2020-08-12
- 摘要：Spectral response is one of the important parameters of CCD. In order to study the effects and physical mechanism of spectral response of CCD being affected by radiation environmental, the different particles irradiation tests are done, also the degradation form of CCDs' spectral response and degradation of CCDs' light response on typical wavelength are investigated. The decays of spectral response in CCD exposed to radiation environment consist of total ionizing dose effects and displacement damage effects. This paper investigated the degradation law and physics mechanism of spectral response in CCD irradiated by 60Co-γ and proton. In view of the typical CCD optical response wavelength of 460 nm (blue light) and 700 nm (red light), the physical mechanism of the degradation of CCD spectral response was analyzed from the radiation induced damage defects. The results suggest that the CCDs' spectral response curve change induced by 60Co-gamma ray is due to the dark signal increases. The CCDs' spectral response degradation induced by proton is significantly higher at 700 nm wavelength light response than at 460 nm. The degradation is more obvious at 10 MeV proton than 3 MeV proton. So it is clearly that displacement damage defects easily lead to CCD spectral response degradation. The results indicate that the total ionizing dose effects inducing a global degradation of spectrum response, while displacement damage inducing the contrast of spectrum response on different wave length significantly.关键词：charge-coupled devices;total ionizing dose effects;department damage;spectral response103|49|2更新时间：2020-08-12
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Raman Spectra Enhancement of Dioxin-like Polychlorinated Biphenyls (PCBs) Based on Molecular Docking
摘要：To find the structural variables that can enhance the vibrational intensity of Raman spectra of dioxin like polychlorinated biphenyls (PCBs) from the molecular structure point of view, the structures of 13 dioxin-like polychlorinated biphenyls (PCBs) were optimized by density functional theory (DFT) at B3LYP/6-31G(d) level. The molecular structures of 13 kinds of PCBs were extracted after docking with biphenyl dioxygenase (Bpha, PDB:3GZX) by molecular docking technique, and the Raman spectra vibration intensity and frequency of the PCBs before and after docking were calculated. The results show that the Raman vibrations of 13 kinds of PCBs are benzene ring deformation, C-C stretching, C-H swing, C-H stretching and various forms of coupling, the Raman vibration intensity is the strongest between 1 632.77-1 652.06 cm-1 and the benzene ring deformation is the characteristic vibration. The results of molecular docking show that the dihedral angle of PCBs after docking has obvious change, resulting in the increase of the Raman vibration intensity by 2.9%-213.98%, the Raman peaks between 1 631.57-1 651.94 cm-1 blue shifting. The dihedral angle and the Raman vibration intensity show a certain degree of linear relationship. The Raman vibration intensity is enhanced with the decreasing of the dihedral angle. It can be used to improve the sensitivity of PCBs identification by adjusting the dihedral angle of PCBs. The results can provide a theoretical basis for the detection of PCBs Raman spectroscopy.关键词：dioxin-like PCBs;Raman spectroscopy;molecular docking;dihedral angles110|80|0更新时间：2020-08-12
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