最新刊期
卷 23 ， 期 6 ， 2002
- 摘要：The studying results of AC/DC Electroluminescence(EL) phosphors, devices, physical mechanism and application in China are summarized. China is the country that study and know well AC/DC EL technology independently after England. The main arts of AC/DC EL in China have caught up with advanced level in the world. Recent years, a new method of cupper coating and a unique forming art have been put forward successfully. The production efficiency of cupper coating is raised above 10 times and the panels with single emissive area of 1 200cm2 can be formed only in one minute. The physical mechanism of forming process and the decay of luminance, the reason of forming emission region and its random were studied. The characteristics of AC/DC EL panel under AC voltage were studied thoroughly. Under AC voltage of 110V, 60Hz operation, the brightness of AC/DC EL panel is higher above 10 times than that of conventional powder ACEL panel. A computer displays of 1m2 and a high resolution portable computer display had been developed in 1985. By means of ACEL characteristics of AC/DC EL panel, many kinds of display with high brightness and long lifetime under AC commercial power operation have been developed.关键词：thick film AC/DC flat display;copper-coating;forming process;ACEL characteristics of DCEL81|67|1更新时间：2020-08-11
- 摘要：The effects on optical and electric properties of InGaAs(P)/InP MQW structure by Implant Induced Composition Disordering (IICD) and Impurity-Free Vacancy Diffusion (IFVD) are investigated intensively. The experimental results indicate that the band gap blue shift of MQW structure by IICD depends on ion dose and following annealing conditions such as annealing temperature and annealing time. The band gap blue shifts are also influenced by lattice stress. The blue shift of the sample with compressive stress is larger than that of the sample with tensile stress. The band gap blue shift of MQW structure by IFVD depends on the compounds of dielectric layer and the consequent annealing treatment, such as annealing time and temperature. It also depends on the combination between semiconductor cladding layer and dielectric layer. The combination of InGaAs and SiO2 creates larger blue shift than that of InGaAs and Si3N4. On the contrary, the combination of InP and Si3N4 creates larger blue shift than that of InP and SiO2. The effect of doped dielectric layer has also been investigated. A large blue shift of 224meV is caused by phosphors doped dielectric layer SiOxPyNz. The SIMS characterization indicates that the quantum wells intermixing caused by IICD or IFVD probably is the main reason for the band gap blue shift.关键词：superlattice;quantum well;ion implantation;impurity-free vacancy diffusion92|110|1更新时间：2020-08-11
- 摘要：Methods of photoluminescence(PL) photovoltage(PV), and time-resolved spectrum(TRS) are applied to study InGaAs/GaAs strained quantum well. We discover single-quantum well(SQW) and multi-quantum well(MQW) have different spectral properties; and spectral intensity of MQW is much higher and spectral full width at half maximum (FWHM) is larger than those of SQW, but spectral FWHM of SQW increases more quickly than that of MQW, which is caused by exciton-LO phonon coupling. The peaking energy of 11H obtained from PV spectrum has a little redshift compared with that from PL spectrum, which is called Stokes shift. TRS at different temperature shows luminescence delay of all three samples accords with one order at low temperature. But when the temperature is up to 70K,luminescence delay of Sample A accords with two orders, while luminescence delay of Sample B and Sample C still accord with one order. Luminescence delay with one order means one process of luminescence delay and luminescence delay with two orders means two processes of luminescence delay. Considering the different width of the three samples, we know that there are more than one sublevels in conduction or valence band of Sample A. But for the narrower width of quantum well, Sample B and Sample C have only one sublevel in conduction or valence band. As the temperature rises to 70K, KT approximates the transition energy from the first sublevel to the second one in valence, which suggests that transition may occur among valence interbands of Sample A and this transition causes luminescence delay of Sample A according with two orders when the temperature is up to 70K. We also observe that PL lifetime of MQW is longer than that of SQW,which is due to quantum tunneling effect in MQW at low temperature. The transition peaks of PV spectra and PL spectra have been identified compared with the theoretical calculation by Kronig-Penney model.112|112|0更新时间：2020-08-11
- 摘要：The epilayer of vertically stacked, self-assembled InAs Quantum Dots (QDs) was grown by MBE with solid sources in non-cracking K-cells, and the sample was fabricated to a FET structure using a conventional technology. A quantum dot (QD), the behavior of which is to capture and emit carriers like a giant trap, is studied using deep level transient spectroscopy (DLTS) technique. The electrons and holes in the QDs are respectively emitted from the relevant energy levels to the conduction and valence bands of the barrier layer with increasing measurement temperature, and the thermal emission energies from the QDs are related to their discrete energy levels. The 5-period vertically stacked InAs QDs in the barrier layer of a field-effect type structure were measured, and the results were found to correspond to the capacitance-voltage and photoluminescence properties. At 77K and room temperature, the threshold voltage shift values are 0.75V and 0.35V, which are caused by the trapping and detrapping of electrons in the quantum dots. Discharging and charging curves form a part of a hysteresis loop exhibiting a memory function. The electrical injection of confined electrons in QDs products the threshold voltage shift and memory function with the persistent electron trapping, which shows the potential use for a room temperature application.关键词：self-assembled quantum dots;molecular beam epitaxy(MBE);deep level transient spectroscopy;field-effect transistor;non-volatile memory93|92|0更新时间：2020-08-11
- 摘要：Using DC reaction sputtering, ZnO films were deposited on Si and quartz substrates, respectively. The reflection and transmission spectra of ZnO films have been measured in order to detect the absorption edge and absorption peaks. A special system was designed to measure the reflection spectra of ZnO films deposited on Si substrates at vertical incidence. It is found that the ZnO films deposited on Si(100) or Si(111) substrates have the same absorption edge, whose wavelength is at 370nm, corresponding to energy of 3.35eV. This value is similar to the band-gap of ZnO crystal. Measuring the transmission spectra of ZnO films deposited on quartz substrates, the absorption edge is also at 370nm. It is indicated that the band-gap of ZnO film has no variance comparing to ZnO crystal. However, the absorption edge of ZnO film deposited on Si(100) substrate is sharper then that of ZnO film deposited on Si(111) substrate. We also found that the annealed sample has sharper absorption edge then that of unannealed sample. The reason is considered to the crystallinity of ZnO film. Higher crystal quality has sharper absorption edge. In the reflection spectra, an absorption peak was observed between 550nm and 600nm. The location of absorption peak is different for the ZnO film deposited on Si(100) substrate and for the ZnO film deposited on Si(111) substrate. We suggest that it is also resulted from the the difference of crystallinity of ZnO films.关键词：ZnO films;reflection spectra;transparence spectra;band-gap structure132|118|7更新时间：2020-08-11
- 摘要：It makes more attention to the ultraviolet (UV) optoelectronic devices. Up to now, the visible emission and ultraviolet lasing emission of ZnO has been the subject of much research. Although many groups put forward different mechanisms for visible luminescence from ZnO, a suitable mechanism is very difficult to establish. Of course, to carry out ultraviolet lasing emission is what one expects to do. In order to study these questions, high quality nanocrystalline ZnO and ZnO:Mn thin films were prepared by thermal oxidation of ZnS and ZnS:Mn thin films, which were deposited by using low pressure metalorganic chemical vapor deposition technique.In the discussion of visible luminescence mechanism, in order to prove that the oxygen vacancies or defects distribute on the surface of nanocrystallites, we presented the preparation of ZnO thin films doped with Mn and studied the photoluminescence of ZnO:Mn. Together with luminescence spectra, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonant (EPR), core-shell structure of nanocrystalline ZnO was put forward. In this thesis, we put forward that Vo** and [Vo*,electron] or [Vo**,two electrons]complex are luminescent centers of visible luminescence. Passivation on the surface of nanocrystalline ZnO was responsible for an energy potential high enough to prevent surface states trapping the electrons or holes photogenerated, it should block the pathway to form the luminescence centers as the Vo** and [Vo*,electron] or [Vo**. A new visible luminescence mechanism was presented.关键词：photoluminescence;nanocrystalline ZnO thin films;interface layers;surface passivation160|85|11更新时间：2020-08-11
- 摘要：The decay process of photo-generated electrons and shallow-trapped electrons was measured by microwave absorption method while a series of powder material (ZnCd)S:Cu and ZnS:Mn,Cu were excited by ultra-short pulse laser. It is measured that the lifetime of photoelectrons is 1 864ns and that of shallow-trapped electrons is 2 144ns in the material (Zn0.97Cd0.03)S:Cu. The lifetime of photoelectrons is 1 376ns and that of shallow-trapped electrons is 1 888ns in the material (Zn0.83Cd0.17)S:Cu respectively after increasing the concentration of Cd2+ ion. The lifetime of photoelectrons in conduction band only have a decrease of 488ns, thereby it is believed that the concentration of Cd2+ ion has less influence on the lifetime of electron in conduction band. At the same time, it is measured that the peak position of luminescent spectrum shifts toward long-wave band along with Cd2+ concentration enhancing. The material ZnS:Cu undoped with Cd2+ ion shows a luminescent spectrum peaked at 505nm and the luminescent spectrum peaked at 565nm for (Zn0.83Cd0.17)S:Cu doped with Cd2+ concentration at 17%. The shifting range toward long-wave band is 60nm. These said the phenomena are likely resulted from the change of bandgap width of luminescent material due to the present of CdS in the host. The decline of luminance output to some extent is simultaneously noticed with the increase of Cd2+ concentration.For the material ZnS:Mn,Cu, it is discovered that the lifetime of photoelectrons decreased to a large extent from 1 720ns to 432ns accompanied with an increase of brightness during the course of enhancing the content of Cu from 0.02 to 0.5%.The maximum luminance was obtained at Cu content of 0.1% and subsequently the brightness declined with the enhancing content of Cu. Therefore, it is considered that a mass of non-radiative transition which can not make for the luminescence is likely to occur so that it can result in diminished brightness at excessively higher content of Cu. Accordingly, there exists a optimal value of the content of Cu for the luminescent material ZnS:Mn,Cu.关键词：luminescent material;zinc sulfide;photo-generated carrier;microwave absorption technique89|61|0更新时间：2020-08-11
- 摘要：It is discovered by molecular dynamics that a positive-bipolaron in luminescent polymers is split into two polarons by absorbing a photon. Because the energy to create a bipolaron is less than the energy to create two polarons, the main carriers in luminescent polymers are bipolarons. For a positive-bipolaron, both εhigh and εlow levels in the gap are empty, and the valence band is fully occupied. After absorbing a photon, an electron is excited from the valence band to εlow level in the gap. It induces the change of the original atomic configurations and electronic states. Our computer simulations reveal that a positive-bipolaron in luminescent polymers will be split into two polarons after an electron is excited from the valence band to εlow level in the gap. The reason of the split is as follows. A bipolaron or a polaron in luminescent polymers is a composite particle, which has intrinsic structures including atomic configurations and electronic states. Due to the instability of low-dimension, the intrinsic structures of a bipolaron will be changed by absorbing a photon. In a polaron, either of εhigh and εlow levels in the gap is occupied by only one electron, and other states are either occupied by two electrons with opposite spins or empty. Therefore, the spin of a polaron is 1/2. Whereas in a bipolaron, all electronic states, including εhigh and εlow levels in the gap, are either occupied by two electrons with opposite spins or empty. So the spin of a bipolaron is zero. Since a polaron possesses spin magnetic while a bipolaron does not, the Pauli susceptibility will be changed when a positive-bipolaron is split into two polarons due to absorbing a photon. So this phenomenon is photoinduced variation of magnetic susceptibility. It is a new phenomenon in luminescent polymers, and would be of interest both in basic sciences and in technology.关键词：luminescent polymers;photoexcitation;magnetic susceptibility99|73|0更新时间：2020-08-11
- 摘要：Great interest arises from rare earth complexes because the emissions of some rare earth ions exhibit high color purity, strong fluorescent intensity and efficient energy transfer from organic ligands to the central ions through the triple states. When europium ion chelates with some organic ligands, such as β-diketone, carboxylic acid and heterocylic acid, it always exhibits high red color purity and strong fluorescence intensity. In the investigation of europium complexes with carboxylic acids, most attentions were focused on the carboxylic acids containing bezene ring and pyridine ring, such as benzoic acid, phthalic acid, nicotinic acid and 2,6-pyridine dicarboxylic acid etc, but less was concerned with tricarboxylic acid.In this paper, rare earth (Eu3+,Tb3+) complexes with citric acid and 1,10-phenanthroline were prepared. Their compositions were characterized by elemental analysis and FTIR spectra. Their fluorescent properties were studied by fluorescence spectra and fluorescence lifetimes. The results showed that the europium (Ⅲ) fluorescence was greatly enhanced in the complexes of (Eu-Tb)Cit·phen while the fluorescence of terbium(Ⅲ) was greatly quenched. The data of terbium's fluorescence intensity was fitted and the results showed that the intensity was decayed by exponential mode. The fluorescence of europium(Ⅲ) was changed by europium's mole content, a minimal intensity was appeared when Eu3+ :Tb3+=4:6 and a maximal intensity was appeared when Eu3+ :Tb3+=6:4. According to the intensity of Eu3+ and Tb3+, it could be found that the europium's characteristic fluorescence could be largely enhanced when the terbium's characteristic fluorescence was greatly quenched. The fluorescence lifetimes were also measured with N2 laser. The results showed that the lifetime of the Eu(Ⅲ) complex could be prolonged when Tb3+ ion partly replaces the Eu3+ in the Eu(Cit)·phen·2H2O complex and its variation accorded with the fluorescence intensity.关键词：rare earth;fluorescence;citric acid;1;10-phenanthroline116|69|3更新时间：2020-08-11
- 摘要：Luminescence in low molecular weight chromophores is usually investigated in devices in which the small molecules are deposited onto a suitable electrode, or other substrate, from the gas phase. Gaining in high-quality thin films by using this technique is often difficult: an alternative is to employ a common polymer fabrication technique in which a film is obtained by spin casting from solution. This methodology, however, requires a matrix polymer whose function, in principle, can be either that of a purely inert carrier or that of an electro-optically active material involved in the carrier transport and emission from the device. In the present investigation, we extended this concept by employing a specifically designed alternating block copolymer which in the pure state emitted in the yellow-orange part of the spectrum but, in combination with the dispersed small molecular weight dye [2-methyl-6-[2-(2,3, 6, 7-tetrahydro-1H, 5H-benzo[i,j]quinolizin-q-yl)ethenyl]-4H-pyran-4-ylidene]-propane dinitrile (MPD). The overlap of the emission and absorption spectra of the copolymer and of the dye blend to facilitate F rster energy transfer were necessary elements of this design. In our results, it is seen that the photoluminescent spectra from MPD in the PMMA matrix nearly coincide with the corresponding photoluminescent spectra with matrix at 595 and 660nm, respectively. Energy transfer in new blend from new polymer to the dye was suggested by spectral measurements of the single-layer film in which MPD was dispersed in new polymer with ω(MPD)=10% concentration, a value which optimized exciting confinement and minimized concentration quenching at 645nm. MPD dispersed in an alternating block copolymer containing thiophene vinylene chromophore units and inert oligomethylene spacer units provided bright red luminescent emission centered at 645nm. The strength of the emission was based, in part, on efficient energy transfer between the copolymer and the dye.关键词：photoluminescence;copolymer;energy transfer74|80|0更新时间：2020-08-11
- 摘要：Poly(9-vinylcarbazole) (PVK) is a typical hole-transporting polymer and is often used as a host in electroluminescence devices.In this paper, Frster energy transfer from organic molecules (PVK) to inorganic nanoparticles (SiO2) was discussed. SiO2 nanoparticles, which are confirmed to be 60nm using transmission electron microscope (TEM), have been synthesized by sol. The structure scheme of poly (9-vinylcarbazole) (PVK) molecule is shown firstly. The emission of luminescence is the result from π*-π transition of π electrons. Photoluminescence (PL) spectra of the PVK/SiO2 composite film on Si substrates were employed to study the interface effect. In the PL spectra of PVK molecules, three obvious peaks (417, 458, 495nm) can been seen. The emission of 417nm comes from free exciton. The emission of 458nm comes from bound exciton. And the emission around 495nm is correlated to surface defect states. The intensity of short-wavelength emission (about 400nm) is higher than that of visible luminescence (about 495nm). Two luminescence peaks can be observed in the PL spectra of 60nm SiO2 nanoparticles. In contrast to the PL spectra of PVK molecules, the luminescence intensity about 495nm is higher than that about 400nm in SiO2 nanoparticles PL spectra. Furthermore, UV/Visible absorption spectroscopy of 60nm SiO2 nanoparticles was measured. The spectrum indicates that the scale of absorption is wide enough from 200nm to 500nm. The ratio of PVK to SiO2 in the composite was increased orderly in weight. In the PL spectra of different concentration composite films, we found that Frster energy transfer occurred between PVK and SiO2 nanoparticles. Overlap is observed between the UV-Visible absorption spectrum of the SiO2 nanoparticles and the emission spectrum of PVK molecules. We suggest that this overlap is the necessary condition of Frster energy transfer. Further investigation indicates that 40% (the content of PVK in composite in weight) is regarded as an optimized content for Frster energy transfer from PVK molecules to SiO2 nanoparticles. The reason maybe is the surfaces of SiO2 nanoparticles are modified successfully and the disperse of SiO2 nanoparticles is unified in this concentration.关键词：photoluminescent;nanoparticles;energy transfer87|96|1更新时间：2020-08-11
- 摘要：The quantum efficiency of organic light emitting diodes (OLED) is an extraordinary factor of device's luminescence performance. Here, quantum efficiency can be defined by the proportion of the number of photons (exports from device) to the number of electrons (imports into device) per second. On account of enhancing OLED's quantum efficiency, a measurement system must be the basic precondition which can be imposed to measure device's quantum efficiency accurately, therefore, we have designed and established an measurement system (with vacuum unit and measurement unit) which can accurately measure the OLED's quantum efficiency. This measurement system is mainly composed by a series of components which produced by Keithley Corporation. Placing the sample device on the silicon photodiodes before measurement, then the measurement room can be vacuumized (Vacuum environment can improve the device's stability and life-time). In measuring, the measurement software simultaneously controls Keithley-2400 Source Meter and Keithley-485 Picoammeter which can get device-current value and photo-current value respectively via data-acquisition board, then transfers device-current value and photo-current value into the number of electrons and the number of photons, finally the quantum efficiency value can be concluded. At the same time, the computer can finish plotting the device's performance curves (such as: Voltage-Current Curve, Voltage-Photocurrent Curve and Quantum Efficiency-Current Density Curve) according to the above values. Furthermore, in order to prove the availability of this measurement system, we have applied the system in measuring a sample device which contains MEH-PPV with orange light emitting. This sample device's quantum efficiency value can reach 0.39% under 17V.关键词：organic light emitting diodes;quantum efficiency;orange light emission92|78|3更新时间：2020-08-11
- 摘要：BaFBr:Eu2+ is a good photostimulated luminescent(PSL) material. The experiments show that compared with BaFBr:Eu2+, the phosphor BaFBr:Eu2+ doped with Al3+ has strong red-shift PSL peaks. The red-shift mechanism is considered as the replacement of Ba2+ by Al3+ doped in BaFBr:Eu2+ and the location of Al3+ is at next neighborhood to F(Br-) centers. The spectra of Raman scattering and electron paramagnetic resonance(EPR) were used to investigate the structure of F(Br-) centers effected by Al3+. The new Raman peak structure is found at high frequency region due to the fact that Al3+ doped in BaFBr:Eu2+. The site relationship of Al3+ and F(Br-) centers is observed and the spatial correlation between F (Br-) centers and OF- centers was studied by EPR spectra.关键词：photostimulated luminescence;BaFBr:Eu2+;Raman spectra;EPR95|139|0更新时间：2020-08-11
- 摘要：Eu2+ activated aluminates are efficiently luminescent materials. But they are usually synthesized by solid reaction method,which requires high synthesis temperature and repeated firing in reducing atmosphere,and therefore requires expensive equipment and high consumption of energy. Some synthesis methods which are different from solid reaction method have been used in preparation of aluminate phosphors. The aluminate phosphor, SrAl12O19:Eu2+, has been synthesized by the combustion of corresponding metal nitrates and urea at 600℃ furnace temperature,with the excess of urea and a cover above the reaction vessel.The process is energy saving,instantaneous and safe.The product is in hexagonal system and pure phase.The excitation spectrum of the sample is a wide band,of which the strongest peak is at 273nm.The emission spectrum is a band peaking at 395nm.No characteristic excitation and emission of Eu3+ were observed,showing that the Eu3+ had been reduced completely. The result showed that an appropriate excess of urea and a relatively airtight reaction system are beneficial to the gain of the pure phase and one color luminescence product in the preparation of Eu2+ activated aluminate phosphor.When only theoretical amount of urea was added and the cover was not used,the emission of Eu3+ in the product could be observed.Furthermore,the characteristic emission of Eu3+ in SrAl2O4 was also seen suggesting that the product is not in pure phase under the later synthesis conditions.关键词：combustion synthesis;europium;strontium aluminate;phosphor75|50|6更新时间：2020-08-11
- 摘要：The defect, the behavior of dynamic and damping motion of domain walls (D.Ws) in some magnetooptic materials have been studied and summarized, e.g. in books[1,2]. We noted the Gilbert damping coefficient is an order of 10-6 and the D.Ws can be moved under the low frequency field of the amplitude value lower 140A/m in the magnetooptic thin film (BiTm)3(FeGa)5O12[3,4]. In the present paper we report the morphology of D.Ws around the defect in the thin film (BiTm)3(FeGa)5O12 under various applied field. The morphology of D.Ws was taken from the home-made polari-microscope-CCD-computer system. From the morphology we can see that:There are two kinds of defect shown in figures, one is like a dark bar in the morphology and the dark bar can not change under applied fields of present experiment, we named it as "hard defect", it is a intrinsic contaminant; another is a special area located in the convergence of three kinds of D.Ws., we named it as "configuration". Under the dc field which value is less than 200A/m, the configuration has not been changed almost. Under the ac field which frequency is 1Hz or 10Hz, the configuration is like ellipses sometimes. Under the uniform magnetic field sweeping (dH/dt=83.6A/m) with ac field (10Hz,the amplitude 140A/m), the configuration has been changed and the new D.Ws. (made approximately an angle of 120 degree with the parallel D.Ws., shown in Fig.3(b)) will be presented besides the ellipses configuration sometimes. The configurations in the various applied fields can be discussed as follows. We suppose the orientation of the configuration of three kinds D.Ws. is like the Fig.4 (a) under dc field; the direction of composition motion of the three kinds of D.Ws. is a single one (to the right-down in present experiment). Under ac field, there are opposite amplitude of applied field and the phase difference of moving D.Ws., it will make the three kinds D.Ws. to separate (or attract), the area of non-domain walls will be presented. We can see that the photographs shown in Fig.2(a), (b), Fig.3(a) have white area at the convergence of the three kinds D.Ws. and the photography shown in Fig.3(b) has a new D.Ws. (made an angle of 120 degree with the parallel D.Ws.).In summary, (1)there is a convergent area of three direction D.Ws., this area must have a defect, and can be changed to become a white area caused by vanished D.Ws.; (2) around the white area the D.Ws. it can be shaped like ellipses when the applied field is the ac. low frequency field; (3) the new D.Ws. will be presented when the applied field is the uniform magnetic field sweeping with ac field.关键词：magneto-optic thin film;defect;morphology of domain walls;composite field98|49|0更新时间：2020-08-11
- 摘要：New structure of a low intensity X-ray image system is mainly made of plane plate mode X-ray intensifier of single proximity focus and CCD data acquisition and processing system. By the system composition, the paper analyses the image noise source of low X-ray imaging system, and points out that the random noise is white noise which is obeyed by Poisson distribution in the whole body, yet the positive-negative interfering impulse is excited in the some locality. Then the compound methods of the "multi-frame mean + extremum median filter" is submitted which deals with the imaging noise. Firstly, some frame images is superimposed, then mean image is calculated from those images, which is under the principle of noise non-correlation. By the method, the information is enhanced and the noise is compressed. Secondly, based on the standard median filtering algorithm, the extremum median filter is ordered as much as possible to preserving the detail of the image when the noise are removed. That is to say, all the pixels are separated into signal and noise pixels according to the decision criterion given in the following; then, noise pixels are replaced with the median value of their neighborhood in the input image. The decision criterion: if a pixels value is the extremum (max or min) of its neighborhood, it is a noise pixel; else it is a signal pixel. This decision criterion is under such an assumption: inherent relationships exist among neighbor pixels. If a pixels value is far higher or lower than the others' value of its neighborhood, we may consider that it had been contaminated with noise. Else, if it is similar to the others, we consider that it represents an effective signal. By the calculation of PSNP, the methods are supper to any single method greatly. And the effect of image filter is satisfied.关键词：X-ray imaging;noise;multi-frame mean;extremum median filter106|104|6更新时间：2020-08-11
- 摘要：Annealing is one of the important heat treatment technologies, which means that heating something such as crystal, metal, alloy and so on to the critical temperature and cooling slowly after holding the temperature for a given time. Annealing is very important during the course of the crystal growth technology. Through the different annealing treatment we can obtain some important information about the crystal defects. The annealing processes are varied, there is no annealing furnace that can settle for the different need of vacuum annealing and atmosphere annealing.A minitype temperature-controlled annealing furnace with high precision is introduced, which is designed by the Phol Institute of Solid State Physics of Tongji University in Shanghai. This paper describes the furnace in three aspects, which are the configuration of the annealing stove,the design of the fittings at the ends of quartz tube and the operation of the programmable temperature-controller. In allusion to the representative annealing process of the crystal (PbWO4), the selection of the PID parameters and the debugging of the temperature-control program are defined particularly.We use this furnace accomplish the annealing treatments of lead tungstate crystal (PbWO4) at different atmosphere (oxygen and argon atmosphere). The optical absorption or transmission spectroscopy provides enough information about the related defects caused by the different annealing atmosphere. The experimental results of the X-ray excited luminescence spectra also demonstrate that annealing at different atmosphere will bring the different influence for lead tungstate samples.We can find that the luminescence and radiation hardness characteristics of PbWO4 can be obviously modified by oxygen annealing. As we all know that in PbWO4 crystal Pb-vacancy (VPb) and O-vacancy (VO) are the main defects because PbO is easy to volatilize. So we can conclude the luminescence and radiation hardness are connected with VO.关键词：annealing;programmable temperature-controller;PID adjustment83|67|0更新时间：2020-08-11
- 摘要：Evaporation, the classical method of thin film deposition, is still commonly used for the production of optical coatings today. The technique of electron beam evaporation delivers a high rate of deposition. Three dimensional or curved substrates are also coated by e-beam evaporation in order to achieve good film thickness distribution. Because of the low energy of the condensing particles the packing density of thermally evaporated films is very low. The achieved film properties are quite different to those of the respective bulk materials. The typical columnar microstructure of many metals and oxides has been investigated by various workers. The low packing density implies that the optical constants and mechanical properties are inferior to those of the bulk materials. Deposition processes using higher particle energies can improve the film properties. With ion assisted deposition, a growing thermally evaporated film is bombarded with an energetic ion beam. Due to the momentum transfer from the incoming ions to the condensing molecules, the mobility of the particles is increased significantly. This results in higher packing densities and improved mechanical properties. A wide range of materials and completed layer systems have been investigated by many laboratories. The limited ion current and beam size of the available ion sources reduces the useful substrate area in comparison to conventional evaporation. This is not compatible to the needs of a high throughput production. Most ion sources use hot filament cathodes and extraction grids with limited life time especially when introducing oxygen into the ion source. Many oxides require ionized oxygen during film deposition in order to get fully oxidized films with low absorption losses and high packing densities. With the newly developed high power plasma ion assisted deposition we have overcome these problems. This paper mainly discusses the performance specification of plasma source (GIS), technology and quality of TiO2 coatings and the technology for antireflection coatings deposited with plasma-IAD.We can draw a conclusion that the refractive index of TiO2 film will have different values with the anode current changing and they are 2.25, 2.37, 2.39, 2.42 and 2.43 at wavelength of 520nm respectively. The reflectance of the antireflection coating is lower than 2% in the wavelength range between 450nm and 750nm.关键词：plasma ion assisted deposition;optical coatings102|66|2更新时间：2020-08-11
- 摘要：Trivalent erbium ions doped zirconia nanocrystal was prepared by co-precipitation method. X-ray diffraction analysis was used to determine the crystal structure. The grain sizes were calculated to be about 10 nanometers by Scherrer's equation. Raman spectra showed that the phonon energy of the host was low. Under the excitation by a 980nm laser diode, the sample presented a strong green emission as well as a weak red emission of up-coversion luminescence.关键词：up-conversion luminescence;trivalent erbium;zirconia;nanocrystal84|73|3更新时间：2020-08-11
- 摘要：Silicate of type Y2SiO5 is well-known host for the activation with trivalent rare earth ion. The luminescence of these phosphors are very efficient both under cathode ray and UV excitation. But, Y2SiO5: Eu3+ does not complete that series, it shows a moderate red luminescence.It was found the red emission can be enhanced considerably by the simultaneous introduction of a high concentration of Tb3+. The luminescent materials with Eu3+ and Tb3+ co-doped were synthesized by sol-gel process,using TEOS and Y2O3 and Eu2O3.The luminescence of Eu3+ and Tb3+ in Y2SiO5 were studied, using Eu3+ and Tb3+ codoped samples. Energy transfer studies have been made also in Eu3+ and Tb3+ codoped Y2SiO5 system. The results show that Y2SiO5:Eu3+ yields a moderate brightness, the emission comes from 5D0 with the hypersensitive transition 5D0→7F2 as the most prominent group at about 611nm. The Tb3+ emission is mainly from 5D4→7FJ(J=4～6) and a smaller contribution from 5D3→7FJ(J=4～6) transitions in Y2SiO5. Sensitization of Eu3+ emission by Tb3+ is possible in Y2SiO5 hosts. The introduction of a small Tb3+ concentration results in the simultaneous emission of Tb3+ and Eu3+. The efficiency is enhanced considerably by simultaneous introduction of a high Tb3+ concentration. Enhancement of the Eu3+ (5D0→7F2) emission and a decrease of the Tb3+ emission have been observed as a result of energy transfer from Tb3+ ion to Eu3+ ion. In the spectra, the spectral positions of the Tb3+ emissions and the Eu3+ excitation bands have good energetic overlap for several spectral regions, the excited levels 5D4 of Tb3+ and 5D0 of Eu3+ are involved. The observed strong enhancement of the Eu3+ emission for high Tb3+ content is easily explained by the energy transfer effect.关键词：Y2SiO5：Eu3+;Tb3+;luminescence;energy transfer97|96|7更新时间：2020-08-11
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