最新刊期
卷 25 ， 期 2 ， 2004
- 摘要：The band gap of the MgZnO alloy composed of MgO and ZnO can be changed in the range from 3.3～7.9 eV.This material has potential applications in short wavelength opto-electronic devices.ZnO/MgxZn1-xO quantum wells and superlattices can be used in the semiconductor lasers,photodetectors and other opto-electronic devises.In the present paper the developments of the investigation on luminescence characteristic for MgZnO thin films are reviewed.The preparation techniques,luminescence characteristic and corresponding physical mechanisms for the MgZnO alloys are introduced.The ZnO/MgZnO superlattices and quantum wells fabricated on different substrates are described.The Mg content and temperature dependence of the luminescence characteristic are discussed.关键词：MgZnO thin film;quantum well;superlattice;photoluminescence;stimulated emission91|77|9更新时间：2020-08-11
- 摘要：Zinc oxide(ZnO)film has been interested by more and more researchers,because of its wide handgap(3.3 eV)and strong exciton binding energy(60 meV).These properties make ZnO have some potential applications in photonics area,such as UV photo-detectors and emitting diodes.In order to fabricate optoelectronic devices,two problems should be resolved.One is the epitaxy of ZnO crystal film,and another one is the p-type doping.This paper mentions the possible methods for epitaxy of ZnO crystal film and p-type doping.We have used Zn buffer layer to improve the quality of ZnO film deposited on Si substrate,according to multi-lattice marched principle.Moreover,we proposed to use SiC buffer layer for depositing ZnO film on Si substrate,because of many advantages possessed by SiC.For p-type doping of ZnO film,there are some difficulties:(a)p-type doping will raise Madelung energy;(b)self-compensation effect prevents national n-type ZnO return to p-type;(c)acceptors have insufficient activation in ZnO films by using p-type impurity alone.The codoping method using group V elements and group Ⅲ elements as codopants may be favorable to solve these difficult,example using N:Ga=2:1.It could increase the incorporation of the acceptors due to the strong attractive interactions between the acceptor and donor dopants.It also could lower the energy levels of the acceptors and raising those of the donors in the bandgap.Then the acceptors can be ionizable easier.关键词：ZnO film;hetero-epitaxy;p-type doping82|65|12更新时间：2020-08-11
- 摘要：Zinc oxide is an important functional and navel material of Ⅱ-Ⅵ wide bandgap semiconductor.ZnO thin films has a direct bandgap of 3.37 eV with exciton binding energy of 60 meV,and is being considered as a new kind of rapidly developing photoelectric material follows after ZnSe,GaN based materials,and showing enormous developing prospect for applications in the field of LEDs,LDs,and UV detectors.Various growth techniques of ZnO thin films have been extensively studied,including,magnetron sputtering,PLD,MOCVD,MBE,spray pyrolysis,and sol-gel methods,etc.The sol-gel process is regarded as a powerful and cost-effective technique for fabricating nano-materials,and has been successful used for preparation of various kinds of oxide films,such as PT,PZT,PLT,PLZT,SrTiO3,and ZnO films,etc.However,there are few papers on ZnO nanofilms prepared by sol-gel process and served as the buffer layer for SiC thin film grown on Si substrate by LP CVD.The research results on those issues will be introduced.ZnO nanofilms with highly c-axis orientation were prepared by sol-gel process using zinc acetate(Zn(CH3COO)2·2H2O)as starting material.A colorless transparent,homogeneous,stable and undoped ZnO sols with a concentration of 0.2～0.5 mol/L were obtained and served as the coating solutions.Si(100),Si(111)and c-plane sapphire were used as substrate.The wet films were spin-coated on substrate at a speed of 3000 r/min for about 40 seconds,and pre-heated at 150℃ for 30 minutes after each coating,and post-heated in air at different temperature from 500～900℃ for an hour.The prepared ZnO nanofilms are colorless,transparent,homogeneous and crack-free,mirror-like films.The microstructures and the surface morphology of ZnO nanofilms are investigated by XRD,AFM,SEM,Hall analyzer,and ellipsometer etc.The grain size,roughness,refractive index and thickness of ZnO nanofilms were measured.The results showed that the orientation of ZnO nanofilm samples are highly caxis oriented,and it was a surprised that the ZnO(002)diffraction peak of the sample prepared on Si(100)substrate and post-heated at 600℃ is evidently shift from the normal position 2θ=34.42°to the lower angle direction at 2θ=32.90°,the shift value is-1.52°,and the strength of this peak is the strongest,and also in the left side of this peak,i.e.2θ=32.64°,there is an unknown diffraction peak.This can be attributed to the microstructure changes occurred in ZnO nanofilm samples.The strength of ZnO(002)diffraction peak is decreased with increasing post-heated temperature from 600℃ to 900℃.The surface morphology of ZnO nanofilm samples post-heated at different temperature is quite difference,some are similar to the quantum dots,and others are quite flat.Two kinds of SiC thin films had been grown on n-type Si(100)substrate using undoped ZnO nanofilm as buffer layer by low pressure chemical vapor deposition.The structure and electrical properties of SiC/ZnO/Si(100)samples had been measured and analyzed.关键词：ZnO thin films;sol-gel process;nanofilms;wide handgap semiconductors108|98|2更新时间：2020-08-11
- 摘要：ZnO film is attracting more attention because of its ultraviolet emission at room temperature and its potential applications in ultraviolet photoelectron devices in recent years.For the applications preparation of good-quality ZnO films and strong ultraviolet emission in films are requested.Annealing in different ambiences is a good method to improve the quality and to change the stoichiometrical composition.ZnO films were prepared by direct current reaction sputtering and annealed in different oxygen partial pressures(PO2).The laser lasing on the films was observed from the time resolution spectrum.X-ray diffraction analysis shows that the crystal constants decrease and the gain sizes of films increase with PO2,these analysis and images of films by atom force microscopy show that the qualities of ZnO films were improved by annealing in oxygen ambiences.The influences of annealing PO2 on photoluminescence(PL)and its relation to native defects were investigated also.We found that the intensities of ultraviolet photoluminescence were increased with oxygen partial pressures in certain range of PO2 due to the improvement of the structure of films.But in higher PO2,ultraviolet intensities decreased and green intensities increased instead.We suggest that more excitation energy was transferred to green center because of the generation of more acceptors in higher PO2 that these acceptors act as green emission center in the films,the refore UV was decreased,green was increased.The compositions analyses in depth of samples A and E by Auger electron spectra show that A film(annealed in pure N2 ambience)has stoichiometry of [Zn]/[O]>1 and Samples E(in pure O2)has that of [Zn]/[O]<1,it indicates there are more donor defects in Sample A and more acceptors in Sample E.The I-V curves of the junctions Sample E indicates the more acceptors generated in the ZnO film and may inversed to p-type semiconductor due to annealing in higher PO2.关键词：ZnO films;ultraviolet photoluminescence;defects;toichiometry93|75|2更新时间：2020-08-11
- 摘要：ZnO is a direct wide-band gap semiconductor with WZ crystal structure.Due to the low growth temperature and high exciton binding energy(60 meV)at room temperature,it is an ideal semiconductor material with blue light enission.As the development of semiconductor growth technology,high quality ZnO can be obtained,and the research in ZnO attracts much more attention again.In this paper,high quality ZnO thin films on sapphire substrate have been obtained by MOCVD system designed by ourselves.At the same time,the properties of annealed and doped ZnO films have been investigated in details,and good results have been achieved.According to the principle of MOCVD and in order to solve the problem in ZnO growth process,new-type plasma enhanced MOCVD system has been designed and fabricated.The precursors(DEZn and O2)has been introduced into the reactor by two gas lines,respectively.And the precursors arrive to the surface of sapphire substrate by two separated special injectors.The substrate holder can be rotated at high speed and is uniformly heated by a special resistive heater.In order to balance the thermal flow,N2 is introduced into the reactor uniformly from the upside of the reactor.All above design can reduced the pre-reaction of DEZn and O2 during the ZnO growth and uniform ZnO films may be grown by this MOCVD system.Furthermore,the plasma generator has been added to the MOCVD system in order to improve doping efficiency during ZnO growth process and to obtain high resistivity or p-type ZnO films.High quality ZnO films have been firsly grown on sapphire substrate in optimized growth condition by MOCVD.At the same time,the doping properties of NH3 in ZnO film grown on R-plane sapphire were also firstly investigated.After optimized the growth conditions,only<110>oriented ZnO film were obtained under NH3 flux of 80 sccm.Furthermore,the FWHM of ZnO(110)XRD peak is only 0.50°.The AFM images sbow that the surface of the film is the most smooth.Up or low the flux,the surface will become rough and the crystal quality also decreases.The Hall measurements show that the sample grown under NH3 flux Of 50 sccm is low p-type conductor with the resisitivity 102Ω·cm,hole concentration+1.69×1016cm-3 and mobility 3.6cm2·V-1·s-1.The XPS spectra show that nitrogen and zinc atom forms N-Zn bond under NH3 flux of 50 sccm.As the flux increase,some hydrogen atom is introduced into ZnO film,and the conductivity change into n-type.The sample resistivity is up to 108Ω·cm under NH3 flux of 80 sccm.关键词：plasma-assisted MOCVD system;high resistivity p-type ZnO film;Zn-rich growth85|97|2更新时间：2020-08-11
- 摘要：Well-aligned ZnO micro-rods have been prepared on Al2O3(0001)substrate by metalorganic chemical vapor deposition(MOCVD)with Zn(C5H7O2)2 as the reactant source.The crystal quality and optical character of the ZnO were studied.X-ray diffration spectra show that ZnO is strongly c-oriented.The morphology of the sample was obtained by SEM.The images indicated the ZnO micro-rods have hexahedral structure with radius of 0.5～1.5μm.A strong ultraviolet(UV)emission is observed at 81～360 K when sample is excited by 325 nm line of a He-Cd laser.In the photoluminescence(PL)spectra,deep level emission can't be seen,indicating that the micro-rods have higher crystalline guality.关键词：MOCVD;ZnO micro-rod;XRD;SEM;photoluminescence98|84|1更新时间：2020-08-11
- 摘要：ZnO is a multi-function direct wide-band semiconductor material with wurtzite structure.It has potential applications in varistors,phosphors,transparent electrode,optoelectronic devices,blue-purple light devices.n-type low resistivity ZnO is easy to obtain.However,the difficulty of high resistivity ZnO and p type ZnO must be resolved for the purpose of fabricating practical ZnO devices.Although many research groups are working on it,p-type ZnO problem has never been figured out.N is an effective p-type dopant for Ⅱ-Ⅵ group compounds.There are two effects when N is doped in ZnO thin films:providing a shadow acceptor energy level and decreasing concentration of Zni atoms by combining with ZnO.Thus,it is possible to obtain high resistivity and p-type ZnO by doping N atoms in ZnO.There has two kinds of N source,N2 and NH3.In this paper,the behaviors of N2 and NH3 doped in ZnO thin films are investigated.Firstly,N2 was doped in ZnO thin films grown on c-plane sapphire substrate using plasma assisted MOCVD system.Plasma generator of plasma assisted MOCVD system is very efficient to dope N atoms into ZnO films and to obtain high resistivity ZnO thin films.The N2 doped ZnO films have all of properties of ZnO and show high crystal quality,especially in optical properties,which show light-yellow body color.XRD measurement shows a high intensity peak at 2θ=34.6°with a FWHM of 0.148°,which is(002)peak of ZnO.The corresponding value of double-crystal XRD rocking-curve is 0.34°.The emitting peak locates at 3.29 eV in PL spectrum with a FWHM of 100meV.Compared with 0.65Ω·cm of undoped sample,the resistivity increases to 5×104Ω·cm with N2 doping.Secondly,the behavior of NH3 doped ZnO grown on R-plane sapphire has been investigated.After optimized growth conditions,the XED result shows a high intensity peak at 2θ=56.30°with a FWHM of 0.50°,which is<110>peak of ZnO.The AFM photo shows that the surface of the film is very smooth.The roughness is about 3.01nm.Under different NH3 flux,the sasple's,resistivity has different value as well as electrica1 conduction type.The p-type sample was obtained when NH3 flux is 80 sccm with the resistivity of 102Ω·cm,observed by Hall measurement.Finally,we found that the p-type sample has the trend of turning to n-type.This maybe is due to instability of N-Zn bond in N doped ZnO which is investigated by XPS measurements.Consequently,behavior studies of N doping in ZnO are important to achieve high resistivity p-type ZnO thin films.Furthermore,it is maybe possible to obtain better results by annealing samples under protection of N2 or NH3.关键词：MOCVD;ZnO;doping94|48|1更新时间：2020-08-11
- 摘要：Zinc oxide(ZnO)is a wide gap semiconductor with band gap of 3.37 eV and binding energy of 60 meV at RT.This material was expected for ultraviolet emissive device related to exciton effect at RT.For fabrication of high-quality ZnO thin films,most effort was performed.Previous work,including selected lattice match substrate(GaN,bulk ZnO or ScAlMgO4),employed buffer layer(MgO),annealing at high temperature,was successfully made to obtain high-quality ZnO thin films.In this paper,we chose c-plane sapphire(Al2O3)as a substrate of ZnO thin film.At the optimum temperature,the high-quality ZnO thin films were fabricated.During growth process,the high pure Zn source(6N)was evaporated at 245℃ by Knudsen cell and oxygen was cracked by an rf plasma atomic source(13.56 MHz).Both basal pressures of Zn and oxygen were fixed at 5×10-5 and 3×10-3 Pa,respectively.The chemical cleaned substrate was transferred into growth chamber and then was exposed in plasma oxygen atmosphere at 650℃.Reflection high-energy electronic diffraction pattern indicates that flat substrate surfaces appear after plasma oxygen treatment.The ZnO thin films were grown at selected temperature of 650℃.The as-grown sample was further investigated by X-ray rocking curve(XRC),photoluminescence,and Hall effect measure.ZnO single crystal thin films were prepared on c-plane Al2O3 substrate by plasma-assisted molecular beam epitaxy(P-MBE).A flat surface of the sample was obtained by the monitoring of reflection high-energy electron diffraction.The full width at half maximum of ZnO(002)rocking curve is 0.2°,this indicates that the sample is single crysal thin films.From photoluminescence spectrum at room temperature,an intense free exciton emission located at 3.30 eV was observed and no deep level emission appeared in visible region.Absorption spectrum shows the evident absorption peak of free exciton located at 3.36 eV.Carrier concentration of the sample is 7×1016 cm-3 measured by Van De pauw method.This result corresponds with the reported carrier concentration in ZnO bulk crystal.The above results indicate that the high quality ZnO single crystal thin film was obtained.关键词：ZnO single crystal thin film;RF plasma;molecular beam epitacy;sapphire substrate109|65|1更新时间：2020-08-11
- 摘要：Zinc oxide,as one of novel photoelectric materials,has been drawn much attention recently due to its many advantages.For example,its large band gap of 3.37 eV and high excitonic binding energy of 60 meV make ZnO a good candidate for developing short wavelength optoelectronic devices.Furthermore,the p-doping ZnO can be produced and the p-n structure of ZnO can be formed on the silicon substrate,their characteristics make ZnO to be compatible with Si-based integrated circuits.Hence,ZnO film has wider application in optical and electronic industries.ZnO films can be easily prepared by several techniques such as reactive sputtering,chemical vapor deposition,and molecular beam epitaxy.The film prepared by sputtering has good adhesive to the substrate and its composition can be easily controlled in the deposition process.However,as compared to the films prepared by other methods,the stress of sputtering film is more obvious,the grain size is smaller and the defect density of grain interface is rather larger accordingly.Such disadvantages of sputtering film may degrade its physical properties,such as the intensity of photoluminescence,quantum efficiency of emission and respondence of current-voltage(I-V)behavior.Many studies have demonstrated that the thermal annealing process is a conventional way to improve the quality of sputtering film.For example,after annealing ZnO film in high temperature,it was found from the deep level transient spectroscopy(DLTS)and I-V measurements that some deep energy levels,which might depress the intensity of luminescence of the film,could be removed from the film and the electrical properties of the film were also optimized.As to further understand the thermal annealing effect on the properties of ZnO film,in this paper we utilize atomic force microscopy(AFM)and ellipsometry to study the annealing dependence of morphology and ellipsometric of the ZnO film.The results demonstrated that the morphology varies little when annealing temperature Ta<850℃.However,it is found the grain size to grow larger apparently after annealing at Ta>850℃,and the corresponding distribution of grain size is irregular.Accordingly,the ellipsometric parameters,such as △ and index n,are also changed with Ta.The change of △ and n when Ta<850℃ can be attributed to improvement of the grain structures,variation of the ratio of oxygen and zinc,decrease of the adsorbated oxygen on the film and void in the film,and increase of the film density.On the other hand,when Ta>850℃,decrease of the defect density,especially the decrease of the defects of grain interface should be mainly responsible for the variation of △ and n.关键词：ZnO thin film;annealing behavior;atomic force microscopy;ellipsometry111|76|1更新时间：2020-08-11
- 摘要：We present the results of UV photodetectors fabricated on ZnO epitaxial films grown on c-plane sapphire substrates by plasma assisted MOCVD.The ZnO films with single c-axis orientation and high resistivity are obtained.With plasma apparatus,we also obtain high resistivity ZnO films doped with N.Considering the high photo-conductive characteristics of ZnO,and characteristics of device with MSM structute,such as high responsivity,high speed,little change with bias,simple fabrication technic,easy for monolithic integration,we fabricate the ZnO UV photodetector.The size of the device is 80μm×100μm,the electrode is interdigital.Measurements are performed using a 500 W Xe-arc lamp as light source.Based on the I-V characteristics of ZnO MSM IDT devices,we can conclude that the dark current and illuminated current of the photodetector linearly increase with the increase of the bias.The curve of the spectra-photoresponse of the IDT photodetector indicates that the detector is in response to the ultraviolet wave range and that the peak value is about 375 nm.关键词：plasma assisted MOCVD;ZnO thin film;ultraviolet detector108|83|2更新时间：2020-08-11
- 摘要：In the experiment,reflection spectra of ZnO films,which deposited on Si substrate,were measured.Then,the reflection spectra were used to determine the complex dielectric constant and complex refraction index of ZnO films according to Kramers-Kronig(K-K)relationship.There are two conditions for using K-K method.One is the reflection light from the sample must be perpendicular to the sample surface.Another one is that the reflection spectrum must be over full range of wavelength.Therefore,we designed a special mirror with a small hole in center of the mirror.The radiation beam emitted from the light source was reflected by this mirror,and perpendicularly irradiated the surface of the sample.Through the hole in center of the mirror,the reflection light from the sample surface was detected by a monochromator.The reflection spectrum measured in the experiment was limited in a certain wavelength range.In order to calculate the optical constants by using K-K relationship,we choose an appropriate extrapolation to get the reflectivity for all wavelength.Finally,we calculated the complex dielectric constant and complex reflected index of ZnO films.From the result,it can be seen that the index of ZnO films is almost a constant of 3.5 in the range of visible range,and a peak value(maximum)appears at the wavelength of 430 nm.In the short wavelength,the index of ZnO film decreases and fluctuates between 0.5 and 2.5.These data remain to be conformed,because we suggest that there is not any absorption peak in the short wavelength of the reflection spectra when we use the extrapolation to get full reflection spectra.This supposition must be evidenced by a further experiment.关键词：ZnO films;reflection spectrum;K-K relationship;optical constants135|76|5更新时间：2020-08-11
- 摘要：Lots of investigators' interests,in the problem of an electron bound to a hydrogenic impurity and interacting with the longitudinal optical phonon field of an ionic crystal or a polar semiconductor,have been maintained over years.Since the 1980s,Takuda investigated the optical polaron bound in a Coulomb potential within the modified variational scheme of the LLP theory,some investigators started to study the bound optical polaron in variational physics models from theory or experiment facets,using different methods.Particularly,scholars are not only looking for the new means,but also paying more attention to the properties of the bound optical polaron in variational physics models recently.Chen et al.studied the ground state description of the bound polaron in parabolic quantum wires by the Feynman-Haken path integral.Bouhassoune et al.calculated the binding energy of a bound polaron in a quantum well wire.Es-sbai et al.investigated the impurity bound polaron in a cubic quantum dot with the use of the variational approach.Melnikov et al.applied the adiabatic variational method to calculate the polaron energy shift in a spherical quantum dot.Derieese et al.presented a multilateral theoretical study of bound polarons in oxide compounds,and Satori et al.attained the binding energy of a bound polaron to shallow donor impurity in spherical quantum dot using a vatiational approach within the effective mass approximation.One of this paper's authors by using linear combination operator and unitary transformation methods achieved the energy of the ground state and of the first excited state of the bound optical polaron for different values of the electro-phonon coupling.In the early 1970s,Huybrechts investigated the internal excited state of the bulk optical polaron by using linear combination operator method.The excitation energy of the stong coupling surface polaron was calculated by means of Huybrechts' method by one of the authors.However,few scholars studied the temperature dependences of the bound optical polaron with linear combination operator and unitary transformation methods so far.In this paper,we investigated the temperature dependences of the bound optical polaron in a Coulomb potential with this method.Using the parameters and the coupling constant of the RbCl crystal for the strong coupling,we calculated the vibration frequency,the ground state energy of the bound optical polaron and the mean number of optical phonon.The results show that the absolute values of the ground state energy,the vibration frequency and the mean number of optical phonon are all increase with the temperature's increasing.关键词：bound optical polaron;ground state energy;vibration frequency;mean number of phonon;temperature100|63|0更新时间：2020-08-11
- 摘要：GaP1-xNx alloy is a remarkable and promising semiconductor for its giant band-gap bowing effect and its potential application in optoelectronic devices.In this article,we carried out a series of studies on the optical properties of GaP1-xNx alloys,especially focusing on the samples with composition x=0.24%,0.6%,0.81%,using temperature-dependent photoluminescence(PL)speetra and transient photoluminescense spectra.At 17 K PL spectra,the GaP1-xNx alloys exhibit an obvious tendency of band-gap reduction with increasing composition x.When composition x<0.24%,the NN1 zero-phonon line and its replicas in GaP1-xNx alloys are well resolved,displaying similar characteristic to dilute nitrogen doped GaP;while 0.24%<x<0.81%,the PL peak energy red-shift effect continues and the emission intensity of the NN1 replica region is enhanced relative to the corresponding zero-phonon line due to the carriers transferring effect with increasins composition x.In addition,the PL linewidth broadens and the fine structure is gradually illegible.At higher compositions,the PL spectra shift to lower energy and become wide band emission with long emission tail.The fit to the spectra profiles confirm that several new bound states exist below the energy of NN1 zero-phonon line even when the composition is as low as 0.24%,where the phonon replicas are apparently legible,but the energy of the new bound states might superimpose with the NN1 phonon replicas.At higher composition(x=0.43%,0.6%),the new bound states and the carriers transferring effect are more obvious.While at x=0.81%,it is hard to distinguish the energy position of each bound state,indicating a trend from doping bound states to impurity band.Such trend suggests a lower critical point from bound states to impurity band vompared with references.The activation energy of the new bound states decreases with incleasing composition x from 0.24% to 0.6%,but still keeps at a level of the hole binding energy.That suggests the new bound states still have the properties of N-related bound excitons.On the other hand,the double-exponential decay lifetime of the new bound states reveals the different emission mechanism from that of the NN pairs bound excitons.The conclusion is drawn that the new bound states might be the N-related bound states(for instance,the NNN triplets)below the NN1 bound exciton,or have certain interaction with the NN pairs bound excitons.关键词：luminescence;Ⅲ-Ⅴ semiconductor;band-gap bowing95|55|0更新时间：2020-08-11
- 摘要：Silica nanowire arrays have been synthesized in a large-scale when we successfully grew various Ga2O3 quasi one-dimension structures in the tube furnace,via the simple method of heating the metal Ga.The nanowires are of high purity and highly oriented.Their diameters distribute from 5 nm to 12 nm,with average value of 8 nm and lengths of 300μm.The analysis shows that they are amorphous.The experiments show that the liquid Ga acts as the catalyst and the growth of SiO2 represents some new characteristics,which traditional VLS mechanism does not own.It was also found that the moisture of the flowing argon gas is a key factor for the growth of nanowires.A possible growth model of nanowires is proposed upon these,which is distinctive from the conventional Vapor-liquid-solid(VLS)growth mechanism.Under the optical excitation of 325 nm laser,the sample exhibits two intensive and stable light emissions near the blue light wave bond,which are directly related to the defects and vacancies in the sample.Besides these two peaks,one new infrared peak at about 804 nm was first found in our experiments,whose mechanism is unknown now and will be researched in further.As an excellent optical source,the silica nanowire arrays can find applications in future opto-electronic nanodevices.Additionally,single silica nanowire may be used in scanning near field optical microscope as the alternative probes.Finally,because of the high flexibility of the SiO2 nanowire bundles they can also be used in the future nano-optical fiber,which is one of important segments in the information transfer.So research in the synthesis of silica nanowires and the characteristic of PL of them are of remarkable importance.关键词：silica;nanowire array;photoluminescence99|96|1更新时间：2020-08-11
- 摘要：The purpose of this paper was to investigate the photoluminescence(PL)properties of the composites of porous silicon(PS)/porous alumina(PA)and poly(N-vinycarbazole)(PVK).The spin coating method was used to assemble porous silicon(PS)/porous alumina(PA)with polymer(PVK).The photoluminescence properties of the composites of PS/PA,and PVK were studied.The PL spectra of the composites not only showed the peak that belongs to PS/PA but also showed the peak that belongs to PVK.At the same time,in the PL spectrum of PS/PVK,a new peak was found locating at λ=485 nm.The origin of this peak was discussed.It is possible that this peak origins from the carriers transferring from porous silicon to PVK.PVK could be viewed as a special surface state of porous silicon in the composite of porous silicon and PVK.Carriers might be excited in intern of the silicon crystal and transferring to the surface of PVK.Carriers combined on it and a new emission peak at 485 nm appeared.Furthermore,the location of the peak didn't vary with the quality of PVK.So PVK provided with a stable surface state.The composite of PA/PVK didn't show any new emission peak.But about 20 nm blue shift of the peak of PVK was found after composition.It has been reported that the conglomeration of conjugated polymer can result in the narrowness of energy band(Eg).During the formation of PVK polymer thin film,the conglomeration is inevitable.After PVK polymer is coated on porous alumina,the polymer will enter into the pores of porous alumina.Since the diameter of pores is about 60～70 nm,the surface area of the polymer increases.Furthermore,nano-pore structure of porous alumina prevents the PVK polymer from conglomeration.Thus,the conglomeration of PVK in pores of PVK is less than conventional PVK polymer film.The Eg value of the PVK on porous alumina will become bigger so that about 20 nm blue shift of PL peak of the composite is observed.Therefore,it is concluded that the nano-meter effect of porous alumina brings on the blue shift of PL spectrum for PVK.The results in this paper verified the difference of luminescence mechanism between porous silicon and porous alumina.The carriers of porous silicon are excited in the intern of silicon crystal and combined on the surface of the surface.So the carriers of porous silicon could transfer to PVK and a new PL peak appeared.However,porous alumina owns fixed luminescence center.Its carriers couldn't transfer to other places.And it is impossible for the composite of porous alumina and PVK to show a new PL peak that doesn't belong to not only porous silicon but PVK.关键词：porous silicon;porous alumina;PVK;photoluminescence95|78|1更新时间：2020-08-11
- 摘要：Synthesis of Y2O2S:Eu3+,Mg2+,Ti4+ red phosphor by flux fusion method was presented.The X-ray diffraction analysis showed that the crystal structure was Y2O2S.the decay curves of Y2O2S:Eu3+ and Y2O2S:Eu3+,Mg2+,Ti4+ were measured,the afterglow time of Y2O2S:Eu3+ was about 30 min,the afterglow time of Y2O2S:Eu3+,Mg2+,Ti4+ was over 70 min.The emission spectra and excitation spectra of the phosphor were acquired.The emission spectra showed that Y2O2S:Eu3+,Mg2+,Ti4+ had narrow emission peaks:the emission peaks at 583.5 nm(5D0→7F0);595.5,597.3nm(5D0→7F1);617.3,627.0 nm(5D0→7F2);705.3,707.0 nm(5D0→7F4)ascribed to Eu3+ ions transition from 5D0→7FJ(J=0,1,2,3,4);556.4 nm(5D1→7F2);587.6,589.5 nm(5D1→7F3)ascribed to Eu3+ ionstransition from 5D1 to 7FJ(J=2,3);467.8,469.5 nm(5D2→7F0);475.5,477.5 nm(5D2→7F1);488.3,490.6 nm(5D2→7F2);513.0,514.0 nm(5D2→7F3);540.1,544.3 nm(5D2→7F4)ascribed to Eu3+ ions transition from 5D2→7FJ(J=0,1,2,3,4);497.0 nm(5D3→7F5)ascribed to Eu3+ ions transition from 5D3→7FJ(J=5)were found.The characteristic red emission at 617.3,627.0 nm were due to the dominant 5D0→7F2 electric dipole transition,and the emission at 627.0 nm was dominant.Due to the function of weak crystal field,the emission ascribed to energy transition 5D1→7F3,5D0→7F1 and 5D0→7F4 divided.The excitation spectra of Y2O2S:Eu3+,Mg2+,Ti4+ showed that it had excitation peaks at 345,260,396,468,540 nm,etc.The excitation peak at 345 nm was ascribed to the absorption of charge transfer(Eu3+-O2-,Eu3+-S2-).The excitation peaks at 468,520,540 nm were ascribed to the representative 4f-4f energy transition of Eu3+ ions.The thermoluminescence glow curves of Y2O2S:Eu3+ and Y2O2S:Eu3+,Mg2+,Ti4+ were measured.The adulteration of Mg2+,Ti4+ affected the afterglow characteristic of Y2O2S:Eu3+,Mg2+,Ti4+ distinctly.The thermoluminescence glow curve of Y2O2S:Eu3+ could be fitted to the peaks at 237,276,301 K.The thermoluminescence glow curve of Y2O2S:Eu3+,Mg2+,Ti4+ could be fitted to the peaks at 149,215,262,287,334 K.The afterglow characteristic of Y2O2S:Eu3+ and Y2O2S:Eu3+,Mg2+,Ti4+ mainly related to the thermal peaks at 301,334 K respectively.The adulteration of the Mg2+,Ti4+ could enhance the afterglow characteristic of phosphor distinctly.关键词：long afterglow;excitation spectra;emission spectra;thermoluminescence;Y2O2S：Eu3+;Mg2+;Ti4+94|47|4更新时间：2020-08-11
- 摘要：Based on more inferior Eu solid solution into BaTiO3 at ambient pressure and the reduction of high pressure,under extreme conditions with high pressure of 4.0 GPa and temperature of 1090℃,the solid state reaction was adopted in order to explore new-type functional Eu-doped BaTiO3 ceramic materials,and its synthesizing law,structural and electrical structural characteristics.XRD(X-ray diffraction pattern)results showed that homogenous solid solutions of Ba1-xEuxTiO3 with gray black body color were prepared from x=0.1 up to 0.4,A-site Ba2+ ions were homogenously instituted by Eu ions.The x=0.1 sample was indexed as tetragonal;x=0.2 as diphase of tetragonal and cubic;x=0.3 and 0.4 samples were cubic.The crystal structure transforms to higher structural symmetry with increasing Eu content.As x was increased to 0.5,the ABO3-type perovskite phase and pyrochlore-type Eu2Ti2O7 phase coexisted in the sample.It was determined from XRD data that all Ba1-xEuxTiO3 samples crystallized with size of few tens of nanometer.XPS(X-ray photoelectron spectra)analysis indicated that due to the reduction of high pressure and requirement of charge equilibrium,part Eu ions were reduced as metastable Eu2+ ions(4f7),Eu3+ ions and Eu2+ ions co-existed in all samples,and their contents were approximately equal.Meanwhile,a large of adsorbated oxygen O- was detected on the surface of the samples.In nano-sized Ba1-xEuxTiO3 ceramics,charge equilibrium is compensated by metastable Eu2+ ions and adsorbed oxygen O-.This work will provide valuable information and open up a new field for further developing Eu-doping luminescence materials.关键词：Ba1-xEuxTiO3;high pressure and high temperature;crystal structure;metastable Eu2+ ions;adsorbated oxygen82|91|1更新时间：2020-08-11
- 摘要：This paper reports the site-selective excited emission,fluorescence and photoluminescence excitation spectroscopy of cubic Gd2O3:Eu3+ nanocrystals with diameters of 15,23,135 nm.The intensity distribution of photoluminescence spectra of Gd2O3:Eu3+ nanocrystal depends on the size of nanocrystal,as a result of strong quantum confinement effect.The position of charge transfer band(CTB)calculated by Jorgensen formula is consistent with the experiment results.The emission peaks of C2 and S6 sites Eu3+ in cubic Gd2O3:Eu3+ are dissolved by the site-selective spectra excited with wavelengths in the CTB.The photoluminescence excitation spectra of C2 and S6 sitesEu3+ CTB are worked out through the site-selective excitation spectra and photoluminescence excitation spectra.Itagrees well with the experiment results.关键词：Gd2O3：Eu3+ nanocrystal;charge transfer band;site-selective excitation spectra95|48|4更新时间：2020-08-11
- 摘要：SrAl2O4:Ce3+,Tb3+ phosphor was an important green luminescence materials.It had many excellent properties such as long persistence of phosphorescence,high quantum efficiency,good stableness and no radiation in the use and preparation.In this paper,the SrAl2O4:Ce3+,Tb3+ phosphor was synthesized by high temperature solid-state reaction at a weak reductive atmosphere.The synthesis of this kind of phosphor generally requires high temperature(i.e.1350～1550℃)and reductive atmosphere which was made by the active carbon powder.The matrix composition,structures and luminescent properties of the phosphor could be affected under different synthesizing conditions,such as calcination temperature,soaking time,temperature-lowering way etc.The samples had been characterized by X-ray diffraction(XRD)analysis,scanning electron microscopy(SEM)and fluorospectrophotometer.Based On the XRD peaks and,the powder phosphors were identified as SrAl2O4 phase,which was monoclinic(α=8.4424 Å,b=8.822 Å,c=5.1607 Å,β=93.415°).The results proved that the phosphors synthesized at different temperature in this work were all α-SrAl2O4.Based on scanning electron photo micrograph,the grain sizes were increasingly amplified with the rise of the temperature synthesized.Excitation and emission spectrum of the SrAl2O4:Ce3+,SrAl2O4:Tb3+ and SrAl2O4:Ce3+,Tb3+ phosphors were tested by the fluo-rospectrophotometer.On the basis of analyzing the excitation and emission spectra,The results of the measurement indicated that after adding Ce3+ to the system of SrAl2O3:Tb3+ the luminescence intensity and afterglow time increases.So Ce3+ sensitized Tb3+ and passed energy to it.关键词：SrAl2O4：Tb3+;Ce3+;excitation spectrum;emission spectrum;energy transfer88|48|8更新时间：2020-08-11
- 摘要：We have found a use for an small size microscopic fluorescence imaging spectroscopy to the identification of petroleum species.This instrumentation consists of microscope,variable interference filter,micro-motion stage,CCD camera,picture acquisition card and computer.The interference filter scans across every pixel of CCD array.The different column pixel in the picture which we get at every step is monocolour partial image under different wavelength,with the step by step,these column monocolour pixels change the wavelength.And finally we cut off and reassembled these images and get the whole monocolour images with different wavelength.The interval of sweep step length decided by the required spectral resolution and the required wavelength interval of different pictures.The limiting spectral resolution was controlled by bandwidth of the variable interference filter.The spatial resolution of the instrument decided ultimately by the CCD,filter and imaging objective.This microscopic imaging fluorescence spectrometer has some excellent characters such as compact structure,higher spatial resolution and spectral resolution,higher scan rate and so on.The microscopic morphologies of some oil core sections were observed.According to three dimension fluorescence spectra features data of some crude oil,we have selected proper excitation wavelengths and emission wave-lengths to distinguish different fluorescence from inorganic mineral and organic hydrocarbons.The high spatial contrast distribution picture of crude oil was obtained.关键词：oily core;microscope;imaging spectrometer;fluorescence90|63|5更新时间：2020-08-11
- 摘要：In the video images and computer graphics,Gamma correction is an important process realizing images vision information of reproduction source objects truly.So,the principle of Gamma correction in OLED/LCD is described.By considering human being's vision non-linear,get the formula of gray and luminance,that is G=K×(L)(1/2.2).At the same time,get the characteristic curve of gray-scale and luminance of CRT relative to OLED and LCD.According to OLED and LCD electro-optical non-linear curves,we adopt normalized method to correction.Besides,in the practical,two conditions are limited.One is the gradient of OLED and LCD electro-optical curves.If their gradient is very steep,the adjacent gray-scale voltage will be very close.Thus,maximum noise voltage is limited in the electrical circuit.Another is the complication of the electrical circuit.If each gray-scale voltage depends on driving circuit directly,it will be very difficult to make the driving circuit to multi-gray scale display.Therefore,usually some regulation voltages of gray-scale are selected.But other gray-scale voltages are selected by row resistors average between adjacent regulation voltages.In fact,the practical gray-scale voltages are an approximation by gamma correction.The more the quantity of regulation voltage is,the better the gamma correction voltages are.Due to the comparability of OLED and LCD correction,here we have an example of correcting TFT LCD of 26.4 cm VGA(line inversion).Source driver IC is μPD16641 of NEC corporation.It has eleven voltages as regulation voltages of Gamma correction.Its driving method is line inversion.We can see its configuration diagram and gamma correction circuit.From the relation diagram of input data,gray-scale and regulation voltages,get external voltage setting values of γ correction in driving circuits were obtained.By comparing the setting and measured values,they are very adjacent in result.关键词：gamma correction;gray scale;line inversion;μPD16641 Chip137|107|5更新时间：2020-08-11
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