最新刊期
卷 26 ， 期 5 ， 2005
- 摘要：Display technology,as a multi-disciplinary compositive technology,has penetrated into various domains and played more and more important role.Especially,in the information times depicted by Internet and wireless communication,both the entrance and exit of "information high-way" require display devices as a platform,this requirement endow with the display technology a more and more arduous mission.Field emission display(FED) is regarded as a flat cathode ray tube (CRT),it is expected to have two-fold technology advantages,its image quality can be comparable to CRTand low power consumption can be comparable to liquid crystal display.The FEDis a vacuum electron device,sharing many common features with the vacuum fluorescent display(VFD) and the CRT.Just like in a VFDor a CRT,the image in a FEDdevice can be created by dragging electrons from a cathode emitters and bombard anode fluorescent screen.In a FEDdevice,the electron source consists of a matrix-addressed array of millions of cold cathode emitters.This field emission array is placed in close proximity to a phosphor faceplate such that each phosphor pixel faces on a dedicated set of field emitters.In addition to the anode and cathode(and gate electrode),a FEDcontains ceramic spacers to prevent the structure from collapsing under atmospheric pressure.Carbon nanotubes(CNTs) resulted from the folding of graphite layers into long carbon cylinders.As a novel form of carbon discovered in 1991,they have attracted much attention because of their unique electrical properties and potential applications.The large aspect ratio together with their high chemical stability,thermal conductivity and high mechanical strength are the advantageous for applications to the field emission display,they have been rapidly recognized as one of the most promising electron field emitters ever sine the first field emission experiments reported in 1995.CNTs as emitters in FEDdevices have been amply demonstrated during the last decade years,and recent developments of production techniques are likely to open future more applications.The research in CNT-FEDtechnologies will give our country an opportunity to participate in international competition in the domain of information display technology.The structure and operating principle of FED,the features that cathode emitters should satisfy,and practical applications of CNTs in FEDdomain are introduced,respectively.The field emission characteristics of CNTs film including turnon field,density of emission current,emission stability and emission site density are discussed in detail.The development history and actuality of CNT-FEDand technical trends are reviewed and prospected,respectively.And the questions with which CNT-FEDfaced are also analyzed.关键词：carbon nanotubes;field emission;display110|80|4更新时间：2020-08-11
- 摘要：With the development of several experimental techniques,for example,molecular beam epitaxy,metal-organic chemical-vapour deposition and electron beam lithography combined with reverse mesa etching,there has been a lot of work devoted to the understanding of hydrogenic-impurity states in low-dimensional semiconductor heterostructures such as quantum wells,quantum wires and quantum dots.In recent years,there has been great interest in investigating quantum dots both theoretically and experimentally.Due to the small structures of QD's,some physical properties such as optical and electron transport characteristic are quite different from those of the bulk materials.The study of the impurity states in these low dimensional structures is an important aspect to which many theoretical and experimental works based.Recent investigations in the reduced dimensionality show the impurity within the reduced dimensionality shows that the impurity binding energy will be enhanced with the deduction of the dimensionality.关键词：parabolic quantum dot;weak coupling;bound polaron;effective confinement length105|96|1更新时间：2020-08-11
- 摘要：Alarge number of researches have shown that the low dimensional semiconductor materials are the ideal nonlinear optical materials.With the progress of crystal growth technology,many low dimensional quantum systems with different dimensions and sizes can be fabricated.So the nonlinear optical effects in the low dimensional semiconductor materials become the important research aspects.Analytic formulas for the linear and third-order nonlinear changes in the index of the refraction are obtained for Morse quantum wells by the compact density matrix method and the iterative procedure.The numerical results are presented for a typical GaAs/A1GaAs Morse quantum wells.The numerical results reveal that,the linear refractive index changes are not related to the incident optical intensity.However,the incident optical intensity has a striking influence on the third-order nonlinear refractive index changes.When the incident optical intensity increased,the total refractive index change will reduce.When the parameter increased,the total refractive index changes will decrease.When the carrier density increases,the total refractive index changes will increase.By contrast,it can be seen that the total refractive index changes equals to zero at the peak value of the optical Absorption.So the large changes in the index of refraction can be obtained when the optical Absorption is small.关键词：nonlinear optics;change in the index of refraction;Morse quantum well;density matrix method161|118|0更新时间：2020-08-11
- 摘要：With the technological progress in material growth,semiconductor quantum wells and heterostructures were obtained experimentally.There has been considerable interest in physical properties of low-dimensional material.Using perturbation method,Hai studied the energy and effective mass of polaron in Q2D system,in calculation,the interface phonon,3D bulk phonon mode,parabolic quantum wells, infinite and finite quantum wells have been taken into account.Zheng studied the ground state energy and effective mass of a Q2D polaron system in a QW by using a modified Lee-Low-Pines transformation.Mori and Ando obtained that the effects for electron and different phonon mode interaction have the same result as bulk phonon mode.Employing second order perturbation theory,intermediate coupling theory and interpolation formula,Sarma discussed the influence of electron-LO phonon interaction on the electronic properties of single two dimensional electronic slab.By using the standard perturbation theory within the Thomas-Fermi approximation,Comas and Rücker calculated self-energy of weak coupling polaron.Li investigated the Stark energy shifts of a bound polaron in a finite and infinite QW by means of perturbation-variation method.Ren carried out the Feynman-Haken path integral theory to calculated the ground state energy of polaron in parabolic quantum well.Eerdun studied the temperature dependence of properties of electron-bulk LOphonon interaction system in a quantum well within the electronic-magnetic fields along the growth axis by means of variational wave-function and harmonic oscillator algebra method and he also obtained the self-energy of the system at a finite temperature.关键词：quantum well;variational method;the mean number of phonons115|83|1更新时间：2020-08-11
- 摘要：As the rapid development of high-energy physics and nuclear medical technology, there has been a great growth of interest in lutetium-based compounds such as lutetium silicate,lutetium aluminate and lutetium oxide.HighZ number(Z=71) of Lu,high physical and chemical stability and high luminescent efficiency of these compounds make them extremely attractive for application in scintillator materials,especially in medical applications.Nanocrystalline Lu2O3:Tb was prepared by combustion synthesis.X-ray diffraction(XRD) spectra,high-resolution electronic microscope(HREM) photographs,Fourier transform infrared spectroscopy(FT-IR),excitation and emission spectra,as well as fluorescent decay curves were measured to characterize the structure and luminescent properties of the samples. The results show that the compound of composition Lu2O3 crystallizes in pure cubic structure.By changing the ratio of glycine to nitrate in the combustion process,the particle size can be controlled in the range from 40 nm to 3nm,and the amorphous area increases while the grain size decreases, which plays an important role in the luminescence properties.Photoluminescence spectra and fluorescent decay curves measured under room temperature show typical excitation and emission peaks of Tb3+.Under UVexcitation,the relative intensity of 5D3→7FJ increases with the decreasing of particle size because of the weakened cross-relaxation process in small-size samples.In the sample smaller than 10nm,the efficiency of energy transfer from host lattice to the activator ions decreases sharply,and there presents a new decay composition of 0.63 ms for the 5D4 energy level,besides the normal one is about 1.9 ms.关键词：nanocrystalline Lu2O3：Tb;photoluminescence;lifetime96|87|4更新时间：2020-08-11
- 摘要：Rare earth doped nanocrystalline phosphors have attracted great interest.The main work concerns the synthesis and the spectral changes of nanoparticles.It has been found that many gadolinium compounds doped with Eu3+ have a higher luminous efficient due to high efficient energy transfer from Gd3+ to Eu3+ ions, moreover,PO43+ groups show high Absorption in VUVregion,thereby,GdPO4:Eu3+could be applied to plasma display panels.Nanocrystalline GdPO4:Eu3+ was prepared by co-precipitation method with EDTA-2Na.The results of XRDindicated that nanocrystalline GdPO4:Eu3+ with the monoclinic monazite type was synthesized at 700 ℃,the XRDintensities of the samples increased with increasing of annealing temperature due to much better crystallization.By applying the Scherrer formula to the full width at half maximum of the(200) diffraction peak,the mean particle sizes could be calculated as 18 nm and 40 nm,for the samples annealed at 700 ℃ and 800 ℃,respectively.The TEM images of the samples show the primary crystal size to be in consistent with the mean particle size obtained from XRD.The excitation spectrum of GdPO4:Eu3+consist of several bands.The bands in the region from 200 nm to 300 nm may be due to the charge transfer band,the other bands from 300 nm to 500 nm are assigned to the Absorption band of Gd3+ and Eu3+ ions.The results of emission spectra exhibit all of emission peaks associated with 5D0→7FJ transition,the relative intensity order of the emission is I(5D0→7F1)>I(5D0→7F2)>I(5D0→7F4),the emission intensities of the samples are increased with increasing of annealing temperature due to much better crystallization,a little broad emission peaks in smaller nanoparticles are mainly from the lattice distortion. The emission spectra under 315 nm excitation display that energy transfer exist between Gd3+ and Eu3+ ions effectively.关键词：co-precipitation method;nanocrystalline GdPO4：Eu3+;excitation spectra;emission spectra;energy transfer107|94|2更新时间：2020-08-11
- 摘要：Lanthanide phosphates represent a class of materials with significant technological importance,and are extensively applied as laser,ceramic,sensor,and phosphor materials.Among various lanthanide phosphate compounds,the lanthanide doped lanthanide phosphates are extremely suitable for applications as phosphors owing to the transition between energy levels of lanthanide ions.The development and application of mercury-free lamps and plasma display panels(PDPs) induce considerable research interest in vacuum ultraviolet(VUV) excitation.Conventional solid-state reaction route requires high temperature calcinations,milling and grinding processes.The phosphor particles obtained by this method have an irregular shape,coarse surface,wide size distribution,and high aggregation.The solution co-precipitation technique was used to synthesize the green-emitting phosphor YPO4:Tb.Results indicate that the YPO4:Tb phosphor particles prepared by co-precipitation technique have almost spherical shape,smooth surface,narrow size distribution in 1~2μm range, and low aggregation.The VUV excitation and emissions under 147 nm excitation are investigated.The VUV excitation spectrum of Tb doped YPO4 suggests that phosphors have a high Absorption near 147 nm,which is ascribed to the host Absorption.The luminous emission of YPO4:Tb precipitates calcinated in 800~1000 ℃ increases with the increase of calcination temperature due to the improvement of crystallinity. The luminous efficiency of YPO4:Tb obtained from solution co-precipitation is higher than that obtained from conventional solid state route.关键词：rare earth orthophosphate;co-precipitation;plasma display panel(PDP);vacuum ultraviolet(VUV)124|64|1更新时间：2020-08-11
- 摘要：The ground state of Ce3+ is 4f15d0,which have only one 4f electron on the configuration.For this reason,the excitation spectrum of Ce3+ ion directly shows the energy state of 5d level.Ce3+ ion can be used as a probe to investigate the f-d transitions of other rare-earth ions in same host lattice sites,since the similarity of the crystal-field effect on the 5d states of different rare earth ions in the sites.The phosphor,Ce3+ ion activated tetra-borate SrB4O7,was prepared by high temperature solidstate reaction technique in present paper.Na+ ion was added to balance the electronic charge due to the different electronic charge value between Ce3+ and Sr2+ ions.The XRDpatterns of the sample Sr0.96Ce0.02Na0.02B4O7 are in good line with the JCPDS standard card 15-801(SrB4O7).The VUV(vacuum ultraviolet) excitation and emission spectra were measured at the VUVspectroscopy experimental station on beam line 3B1B,Beijing Synchrotron Radiation Facilities(BSRF),under normal operating conditions(2.2 GeV,100 mA) at 293 K.The spectroscopic properties of this phosphor are investigated in the wavelength region 130~400 nm.The host-related Absorption is found to be about 155 nm.The five bands corresponding to the 4f1→4f05d1 transitions of Ce3+ ions are identified as 277,242,228,217 and 202 nm in the host lattices.Therefore,the 5d crystal field splitting and the barycenter of Ce3+ in the host lattice are calculated to be 13.4×103 and 43.4×103cm-1,respectively.The doublet emission bands of Ce3+ in the host lattice are observed at 293 and 313 nm.Hence,the Stokes shift is 1971cm-1.Because SrB4O7 and SrBPO5 share iso-structural characteristics: the cations are same,and all of anions are tetrahedral AO4(A=B,P).The spectroscopic properties of Ce3+ in these host lattices are compared and discussed qualitatively.关键词：luminescence;strontium tetra-borate;cerium;vacuum ultraviolet spectra121|53|0更新时间：2020-08-11
- 摘要：Ⅲ-nitride semiconductors hare attracted mach attention recently due to their applications in eletronic and optoelectronic such as high bright blue and green light emitting diodes(LEDs) and laser diodes(LDs).InGaNhas been used as active layers for most nitride LEDs.However,the luminescence mechanism in InGaN alloys is still in question,especially how the structural and compositional homogeneities in the alloy affect on the optical properties of the devices.Photoluminescence properties of InGaN film grown on sapphire substrates by metal organic chemical vapor deposition(MOCVD) were experimentally investigated by means of X-ray diffraction(XRD),transmission spectra and PL spectrum.The peaks of InGaN,InN and In were observed on XRD spectrum. It might be evidence of phase separation and In quantum dots in the sample.Aclear oscillation could be observed on transmission spectra of the sample.As PLspectra excited by xenon lamp,a blue shift of emission peak position was observed.Additionally,when the optical excitation density was increased,the emission peak will split to three peeks.That could be explained by interference due to F-Pcavity arising from surface of sample.The excitation density dependence of PLintensity shows that these emission peaks have different character,the two high energy peak might be originated from local exciton recombination,and the low energy peak is stimulated emission peak,and might be originated from electron-hole plasma(EHP) recombination.Temperature dependence of PLspectra was investigated,peak positions of high energy peak changed with "S-shape" by increasing of temperature,and it is different from character of the low energy peak.The red shift of the peak positions as increase temperature indicated the increasing of refract index.106|73|0更新时间：2020-08-11
- 摘要：Superluminescent diodes(SLDs) can usually be taken as a light source for fiber optic-gyroscopes,wavelength-division multiplexing(WDM) systems and optical coherence tomography(OCT).Because of their high working current density,the output power,lifetime and the spectrum stability may be strongly influenced by the temperature in the active region increasing with injection current.Using MQWs(multiple quantum wells) as active layers can decrease the working current density,reduce Joule heating effect,and increase the differential gain of the device.In this contribution,we calculated the thermal resistance and temperature distribution of InGaAsP/InP MQW SLDs which are influenced by their lateral chip size and composition with two-dimension thermal flow model.The results reveal that when the injection power reaches 1 W,the temperature of active region will be almost 50 K.The width and length of chip also have strong influence on the thermal resistance which can reach two orders of magnitude.The thermal resistance will change from 290 K/Wto 68 K/Wwhen width of chip was increased from 500 μm to 2500 μm.For the length of chip,there is similar result. But there is small effect on thermal resistance for active width.All the results will be useful for structure and composition design of SLD.关键词：superluminescent diode;distribution of thermal resistance;active region124|147|1更新时间：2020-08-11
- 摘要：Annealing is important in semiconductor process.There are some reports on the annealing of ZnO film.Annealing can affect various properties of ZnO films,such as electrical property,optical property and crystalline property.But there still has no complete mechanism of the effects of annealing on properties of ZnO films.The deep-level green emission exists in ZnO films often,and the views on the origin of the green emission has no consistent.Aim to the situation,we systematically study the effects of oxygen and nitrogen annealing on luminescent property of high crystalline quality ZnO films grown on Al2O3(0001) by atmospheric pressure MOCVD.Two sets of small Sample 1 and Sample 2 cut off from ZnO as-grown films are used to be annealed in oxygen and nitrogen,respectively.There is a strong ultraviolet emission at 377 nm and a green emission at about 525 nm for Sample 1 and a strong ultraviolet emission at 377 nm for Sample 2.Then Sample 1 and Sample 2 are annealed for 1 h at 400,500,600,700,800 ℃ in sequence in oxygen and nitrogen,respectively.After annealed for 1 h at every temperature,the luminescent property of every Sample was measured by excitation with 325 nm line of He-Cd laser.Research results show that the deep-level emission at 525 nm vanished as annealed at 500 ℃ in oxygen,but not disappeared as annealed at 500 ℃ in nitrogen.Above 700 ℃,there appeared a new green emission at about 500 nm for Sample 1 and Sample 2 whether annealed in oxygen or in nitrogen.Up to 800 ℃,the ultraviolet emission became very weak,the deep-level emission get very strong,and the peak position of deep-level emission become wider at about 500~525 nm.When all annealed Samples and as-grown Sample 1 were etched by ICP for 15 min,the deep level emissions at 525 nm and 500~525 nm vanished,and the ultraviolet emissions became very strong.These results show that there was large effect on deep-level emission of ZnO films by annealing ambience below 700 ℃;while exceeding to 700 ℃,there was obvious effect on luminescence of ZnO thin film by annealing temperature,but the influence of annealing ambience is no obvious.The deep-level emission at 525 nm is relevant to the surface state of ZnO films,and its origin was discussed by the influence of annealing on the luminescent properties of ZnO thin film.关键词：annealing;thin film;ZnO;MOCVD;green emission109|72|0更新时间：2020-08-11
- 摘要：GaN-based white LEDs are becoming the most promising next generation lighting sources,but the normal encapsulated white LEDs luminous flux declines very quickly.It is very necessary to research on the aging mechanisms of white LEDs luminous efficiency,chromatic properties,and so on.Temperature accelerated aging experiments on two groups of white LEDs have been performed at 80 ℃ and 100 ℃.Both before and after the aging experiments,the current-voltage(I-V) curves of the white LEDs were measured.In the tunneling segment,diffusion segment and reversal leakage current segment of the current-voltage(I-V) curves,the current was increased,while that of the serial resistance segment was nearly unchanged.The cause of these rises was the increase of the threading dislocation density and that the metal impurities assembled around the screw threading dislocations and moved along them.At the same time,the high-frequency capacitance-voltage(Csc-V) curves of the virgin white LEDs and the aged ones at different ambient temperature were measured.In the Csc-V curve,the capacitance decreased in the reversal bias,and it increased in the forward bias.It means that there are some leakage current channels produced by the dislocations.During all the aging time,Chroma parameters were measured every certain hours.The yellow luminescence proportion in the spectrum increased.In the beginning of the aging,the luminous flux decreased slowly,then it decreased rapidly and suddenly.This fact indicated that the accumulation of all degenerating factors could lead to sudden light-off of white LEDs.Finally,by using the Arrhenius relationship,the lifetime of the white LEDs used in our experiments was calculated as 23000 h.关键词：GaN-based white LEDs;aging;current-voltage;capacitance-voltage;luminous flux;lifetime121|106|14更新时间：2020-08-11
- 摘要：Water-colloid cadmium selenide semiconductor nanocrystals were prepared in aqueous solution by using mercaptoacetic acid as stabilizer.The samples were characterized by X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM).The results of XPSconfirmed the formation of CdSe nanocrystals,and the images of TEMdemonstrated that the average size of CdSe nanocrystals was less than 10nm and the aggregation occurred among the nanocrystals.The changes of the XRDpatterns,Absorption spectra and emission spectra of the CdSe nanocrystals prepared for different time were investigated.The XRDpatterns showed that the crystal structure became more perfect with the increasing preparation time.It was found that the emission peak changed from 550 nm to 572 nm, but no distinct changes for the shape and full width at the half maximum of the spectra were observed,but the Absorption peak changed from 443 nm to 483 nm.The extent of the peak changes became less and less with the reaction time,which was attributed to the growth of the CdSe nanocrystals with the reaction time at the initial moment and the control of the growth due to the stabilizer mercaptoacetic acid at the ultimate moment.The emission spectra for the different molar ratios of the reactant were also investigated,and the results indicated that the wavelength of the emission peak shifted to the longer wavelength as the molar ratio of Se2-/Cd2+ increased,and it could be interpreted as followings: In the competition between the reaction of Cd2+with HSe-and RS-,the reaction between Cd2+ and HSe-occupied the predominance with the increasing of Se amount,which made the size of the nanocrystals increase.All the(results) indicated that the varying of the preparation conditions would influence on the luminescence properties greatly.关键词：CdSe nanocrystals;preparation conditions;luminescence properties104|74|5更新时间：2020-08-11
- 摘要：One-dimensional nanoscale semiconductor structures,such as nanowires,nanobelts,and nanorods,have attracted considerable attention due to their interesting fundamental properties and potential applications in nano-scale opto-electronic devices.ZnS,an important semiconductor compound,has wide bandgap energy of 3.7 eV at 300 K.It has been used as a host crystal material in photoluminescence(PL),electroluminescence,mechanoluminescence,acousticluminescence,and thermoluminescence.ZnS also has wide applications in the fields of displays,sensors,lasers,and photocatalysis.The ZnSin nanoscale has been reported to have some characteristics different from the bulk crystal,which may extend its application range.Recently,various ZnS nanostructures had been synthesized,including,nanowires,nanosheets,nanobelts,nanorods,nanoribbons, and nanotubes etc.As a rule,ZnS nanostructures were grown using thermal evaporation method with Au catalyst following vapor-liquid-solid(VLS) growth mechanism usually.In VLS growth process,catalysts play an essential role by forming liquid alloy droplet to provide nucleation sites for nanostructure growth.However,even low impurity concentration will affect the physical properties of semiconductors and the unintentionally doped impurities are detrimental for the device fabrication.Acatalyst-free method to grow vertical aligned ZnSnanorods array was reported.The ZnSnanorods were grown on c-plane Al2O3 substrate by plasma-assisted metalorganic chemical vapor deposition(p-MOCVD) without employing of any metal catalyst.The images of field-emission scanning electron microscope(SEM) and transmission electron microscope(TEM) show that the obtained ZnSnanorods have uniform diameter of 60 nm with the length about 400 nm.Selected-area electron diffraction(SAED) pattern and X-ray diffraction(XRD) pattern measurements indicate that the ZnS nanorod is single crystals with hexagonal structure.In photoluminescence(PL) spectrum of the nanorods,a strong near band-edge emission located at 335.92 nm was observed under the excitation of 325 nm,indicating that the nanorods are of high optical quality.关键词：ZnS nanorods;MOCVD;photoluminescence105|125|0更新时间：2020-08-11
- 摘要：Anodic aluminum oxide(AAO) template has a highly ordered nanoporous arrays with adjustable and controllable pore diameter ranging from 5 nm to 200 nm.AAO template formed by different method has different effort and use.The AAO template used in this article was formed by anodizing aluminum in the oxalic acid of 0.3 mol/L at 40 V and through two-step anodizing oxide method.The AAO template was used to synthesize ZnS nanowire arrays by the method of electrochemical deposition.The production can be proved to be ZnS nanowire arrays by transmission electron microscope electron diffraction image and energy dispersive X-ray spectrum.The TEM image shows that the diameter and length of the ZnS nanowires are about 50 nm and 20 μm,respectively.The photoluminescence spectrum has a great contrast before and after having assembled ZnS nanowires.The photoluminescence spectrum display that the AAO template with ZnS nanowire arrays has two more emission peaks at 409 nm and 430 nm,and they are more intensive under the excitation with longer wavelength.There are different characters comparing with nanoparticles,nanorods and nanowires synthesized by other different methods.One is that the peak intensities are more strong if excitation wavelengths are more longer;the other is that the bandwidth is more narrow.To explain the origin of the ZnS nanowire arrays emission spectrum,the main reason is the transition caused from conduction band to accepter energy rank and from almsgiver energy rank to acceptor energy rank;the two types of luminescence act together so that ZnS nanowire arrays have two close emission peaks;perhaps the other reason is the embellishment of ethanol.Else,the reason of narrow bandwidth is ZnS nanowire arrays have the uniform size distribution.100|98|0更新时间：2020-08-11
- 摘要：The intense visible photoluminescence(PL) of porous Si has attracted much interest as it opens up the possibility of fabricating light-emitting devices based on silicon technology.Silicon carbide,especially cubic phase(β-SiC),is an attractive material for applications in high-temperature and high-power electronic devices for its wide band gap,high thermal conductivity and high electron saturation velocity.The development of SiCfor opto-electronic applications has been the subject of intensive research for a long time.We report a preparation of SiC/Si heterostructure by ion implantation of overstoichiometric C+ to single crystalline silicon substrate with a MEVVA(metal vapor vacuum arc) ion source,then a thermal annealing is performed,β-SiClayer is formed after that,which indicates that surface SiC/Si heterostructure is successfully prepared.The phase transformation characteristics in these SiClayers were studied using FTIRspectroscopy and a de-convolution scheme of the IRspectra into amorphous SiCand β-SiCcomponents.X-ray Photon Spectroscopy(XPS) study the attribute of the Catom,the Atom Force Microscopy(AFM) images show the surface morphology of the annealed samples.The photoluminescence(PL) properties of the as-implanted and annealed samples was studied under the excitation of 355 nm.PLspectra show that there are two main peaks: 430 nm(2.9 eV) and 560 nm(2.2 eV),the PLintensity achieves the maximum at annealing temperature of 900 ℃,2 h.A nanoscale SiC unit quantum confinement theory and surface state theory are used to explain the phenomenon,it was indicated that the nano SiC and bulk SiCplay key role in the PLprocess,and the surface stat of the SiC nanorod also.关键词：nano SiC;ion implantation;photoluminescence102|61|1更新时间：2020-08-11
- 摘要：Silicon carbide nano-rods was synthesized by the pyrolysis of a polysilazane preceramic precursor in the presence of 3%(mass fraction) FeCl2 as a catalyst under 1700 ℃.SEM,XRDand EDXwas employed to characterize their structure and component.XRDpattern demonstrated that nano-rods consist of 3C-SiCas a sole type of crystalline with a plenty of stack fault,and no trace indicated a-SiC polytypes.The ratio of silicon and carbon is estimated as close to 1:1 based on EDXsemiquantitative estimation. Electron microscopy results revealed that the SiCnanorods of 80～200 nm in diameter and several hundred micrometers to a few millimeters in length preferentially grow along(111) direction.Optical properties of nanorods were studied using micro-Raman spectrum,photoluminescence and optical band edge Absorption.In PLspectra an intensive emission at 3.27 eV was observed,and a weak broad emission band was located at low energy side about 2.4 eV,while the optical absorption spectra revealed that there is an optical Absorption edge at the identical energy level mentioned above.However,the optical Absorption spectra showed a complex structure.In order to get more definite information,Raman spectra were measured on these SiCnanorods.Raman spectrum gives a sharp scattering peak at near 800 cm-1 with a shoulder multiply peak at low energy side.Using Gaussian peak fitting,we found that it contains two peaks at 799.6 and 777 cm-1,corresponding to the TOmode for 3C-SiC and a-SiC respectively.Basis of the results of XRD,Raman,optical absorption and PL emission,we conduced to one supposition that the SiC nanorods are mixing-polycrystal with a multi-layer structure.关键词：SiC;nanorod;Raman spectrum;photoluminescence;optical Absorption116|116|0更新时间：2020-08-11
- 摘要：Er3+ photoluminescence(PL) in silicon-based materials has been attracting much interest because of its potential application in Si-based optoelectronic devices.Er3+ ions can be doped into different hosts,such as crystalline silicon,hydrogenated amorphous silicon suboxide(a-SiOx:H),SiO2 film containing Si nanocrystals and so on.In this report PLproperties of undoped and Er3+-doped SiOx films containing amorphous Si nanoparticles were studied.a-SiOx films containing Si nanoparticles were prepared by plasma enhanced chemical vapor deposition(PECVD) using a gas source with mixture of SiH4 and N2O.Erbium ions were implanted into as-deposed SiOx films at 500 keV with a varying dose range of(1~3)×1015/cm2 and then annealed at 300~900 ℃ for 30 s under N2.Visible PLexperiments were performed with a Dilor XY-800 triple grating spectrometer with a charge-coupled device(CCD) detector.The samples were excited by 514.5 nm line of Ar+ laser.The Er3+ infrared PLspectra were measured using FTIR spectrometer(Bruker IFS120HR).The wavelength of Ar+(laser) is 514.5 μm and the nominal laser power was 200 mW.The results showed that the PLintensity from nc-Si in SiO2 at 750 nm is one order of magnitude stronger than that from amorphous silicon clusters in a-SiOx:H,and the PLintensity from Er3+ at 1.54 μm in Er doped a-SiOx:His a factor of 4 higher than that in Er doped SiO2.The PLand crystallinity of a-SiOx:Has function of annealing temperature were also studied.In combination with the Raman measurement,the results show that photoluminescence from amorphous Si nanoparticles also follows the quantum confinement model as in Si-nanocrystals.Our study indicates that a competitive relationship between the light emissions of a-Si clusters and Er3+ in the Er-doped a-SiOx:Hfilm is also present and the films yield efficient Er3+ emission even superior to that of Er doped SiO2 containing Si nanocrystals,suggesting a-Si clusters can also act as both the Absorbing medium and sensitizer in Er3+ excitation as nc-Si in Er doped SiO2.Er3+ emission intensity does not depend strongly upon whether it is nc-Si or a-Si clusters.These results presented here open up a route towards the fabrication of efficient Si-based light-emitting devices.关键词：rare earth;ion implantation;Si-nanocrystals;a-SiOx：H120|142|2更新时间：2020-08-11
- 摘要：Silicon was a main material of micro-electronic devices.It was possessed of better advantage than other semiconductor materials.But semiconductor silicon was not regarded as one of candidates in optoelectronic materials because of its indirect bandgap and lower light efficiency.Thus its application in the optoelectronic devices was restricted.In 1990,Canham published that porous silicon sample fabricated by electrochemical anodization etch possesses exhibits very intense photoluminescence(PL) emission.Its light efficiency is the same comparing with direct bandgap compound semiconductor GaAs.It becomes a popular study target that realizes Si-based photoelectricity integration,because Si-based emitting material may become base material of future photoelectricity integration.Some of rare-earth ions are the better light emitting ions,the rare-earth ion doping into silicon by using ion-implantation was adopted more and more.For studing light efficiency of rare earth doped Si-based films,the beneficial try was made.The photoluminescence spectra of PSsamples and PLspectra of PSsamples treated by HNO3 were studied,the relation of photoluminescence properties and surface structure was discussed.Rare-earth ion Nd is implanted into monocrystal Si wafers at the energy of 99 keVand with a dose of(1×1017 cm-2) using metal vapor vacuum arc(MEVVA) ion implantation.The rapid annealing was made at temperature of 1000 ℃ in the atmosphere of N2 for 20 s.The above samples were treated by anodization method under the conditions: electric current density of 30 mA/cm2;time of 10 min and electrolysis liquid V(HF):V(C2H5OH))=1:1.Then part porous samples were treated by HNO3.PLspectra were measured by F-3010 fluorescence photospectrometer for the above samples at room temperature and compared these PLspectra with those of PS.The results show emission peak of PSsamples doped by Nd is similar with emission peak of monocrystal porous silicon.But the intensity of peak have obviously increase under the same condition of electrochemical anodization etch,the 563 nm emission peak appear blue-shift and its FWHMdecreases.Besides light emission efficiency of the PSsamples that were treated by HNO3 is higher than those of ordinary PS(samples) under the same measuring conditions.Comparing with monocrystal porous silicon,it was found that porous silicon doped by Nd form average nanometer silicon post structure,its light emission efficiency had a elevation.The photoluminescence intensity of those PSsamples treated by HNO3 had a significant improvement.关键词：Nd doped;porous;treaded by acid;photoluminescence100|71|0更新时间：2020-08-11
- 摘要：Conformations have a large impact on the optoelectronic properties for conjugated polymers.The conformations and electronic states as well as optical characteristics of MEH-PPV chains in solid solution,dilute solution,film and nanopore have been investigated with PLand PLEspectra The following conclusions have been obtained.The MEH-PPV chains are separated basically in THF tetrahydrofuran dilute solution.The MEH-PPV chains are aggregated basically in MEH-PPV solid film.There are two conformations of MEH-PPV chains,separated and aggregated conformations,in MEH-PPV/PS solid solution.The aggregated conformation of MEH-PPV increases with increase of MEH-PPV density in MEH-PPV/PS polystyrene solid solution.The MEH-PPV chains form chains bunch in nanopores of porous anodic alumina template.The electronic state and optical characteristics are different for separated and aggregated MEH-PPV chains as well as MEH-PPVbunch.The electronic energy band and the band width of PLE spectra are the widest,and then the energy positions of PL spectra peaks are lowest(about 594 nm) for the aggregated conformation states.On the contrary,the electron energy band and the band width of PLE spectra are narrowest,and then the energy position of PL spectra peaks are highest for the separated conformation states.关键词：PPV and its derivatives;conformations;photoluminescence;nanostructured materials120|108|2更新时间：2020-08-11
- 摘要：Rare earth organic chelate materials attract wide interest for its particular intense emission of rare earth ions compared to the rare earth doped inorganic materials.This is achieved by the organic ligands for its strong Absorption in ultraviolet region and efficient energy transfer to the rare earth ion centers.It leads to lots of applications in the fields of electroluminescence,waveguide devices and fiber amplifiers.During the studies,secondary ligand is found to be of much importance.It can substitute water chelate to reduce the non-radiative relaxation,take part in the energy transfer process,and Absorb photons to affect the Absorption limits.The synthesis and luminescent properties of Sm(DBM)3 doped PMMA(polymethyl methacrylate) with three different secondary ligands: phen,TOPO,TPPO(DBM: dibenzoyl methane,Phen: 1,10-phenanthroline,TOPO: trioctylphophine oxide,TPPO: triphenylphophine oxide) are reported.The emission and excitation spectra of samples with and without secondary ligand are recorded.The emission peaks are assigned to different transitions of Sm3+,as a weak broad band also appears due to direct emission from ligands.The excitation bands of different secondary ligands show obvious shifts compared to that of pure Sm(DBM)3 doped PMMA,the excitation efficiency also varies.Decay curves of the Sm3+ emission of all these samples are measured, and lifetimes of the level 4G5/2 are obtained.The spectroscopic differences among the samples are discussed.The results show that the best secondary ligand here is TPPO.关键词：luminescent properties;PMMA;second ligand;Sm(DBM)3127|78|1更新时间：2020-08-11
- 摘要：The production and development of many diseases is closely related to oxidative damages caused by free radicals.So it becomes one of investigating hotspots that safe and effective antioxidants in plants are searched.And the spectrophotometry for detecting1,1-diphenyl-2-picryl-hyrazyl radical(DPPH·) is a rapid, simple and sensitive method for screening antioxidants.Therefore,the structure-activity relationship of eleven pure and natural flavonoids scavenging DPPH· were studied by using the spectrophotometry for detecting DPPH·.The results showed that all of the eleven natural flavonoids can scavenge DPPH· effectively.The DPPH·-scavenging ability in turn was: quercetin>heliosin>catechin>hyperoside>rutin>kaempferol>morin> isoquercitroside>baicalin>nevadensin>genistein.Therefore it was discovered that the structure-activity relationship of the eleven natural flavonoids scavenging DPPH· was as follows: 1.Bring and/or Aring with adjacent hydroxyl groups could greatly increase their DPPH·-scavenging ability;2.The hydroxyl groups in 4′position on the Bring and the hydroxyl group in6 position on the Aring possessed the high DPPH·-sca-venging activity;3.The DPPH·-scavenging activities of isoflavonoids were weaker than those of corresponding flavonoids;4.The DPPH·-scavenging activities of flavonols were stronger than those of corresponding flavanonols. It suggested that Cring with C2-C3 double bond could enhance its DPPH·-scavenging effect; 5.The DPPH·scavenging ability of flavonoids was closed related to the positions of their hydroxyl groups; 6.When the hydroxyl group at 3 position on the Cring was glycosylated,its DPPH·-scavenging activity was decreased.These results provide a theoretical basis for further exploiting and utilizing flavonoids.130|83|13更新时间：2020-08-11
- 摘要：To understand the interaction between adriamycin(ADR) and transferrin(Tf) solution,the binding reaction between ADR and Tf was investigated by fluorescence and ultraviolet visible Absorption(UV-Vis) spectroscopy methods.The mechanism of the fluorescence quenching of Tf induced by ADRwas determined.The relation between concentration of ADR and F0/F was linear.It showed that the quenching of Tf induced by ADR was either dynamic or static quenching.The ultraviolet Absorption of Tf decreasing in the presence of ADR showed that a nonluminous compound was formed by the interaction of Tf and ADR.So it was confirmed that the mechanism of the fluorescence quenching of Tf induced by ADR was static quenching. Furthermore,we use Stern-Volmer equation to approve it.The equilibrium constants K were measured equaling to(0.98～89.1)×105 while the numbers of binding sites n were 1.09～1.37 at different concentration by means of fluorescence quenching method.The binding distance r=1.94 nm in the interaction of 6.9×10-5 mol/L ADRand 5.6×10-6 mol/L Tf was also obtained according to Frster theory of non-radiation energy transfer.Akind of binary compound of ADRand Tf was formed,providing the instructional meaning for the preparation of oriented drug carried by Tf.关键词：adriamycin(ADR);transferrin(Tf);fluorescence spectroscopy;Absorption spectroscopy132|106|0更新时间：2020-08-11
- 摘要：Asimple and useful driving circuit with constant current source used for the small size PM-OLED display was introduced.This small size(30 mm×38 mm)matrix-type OLED with 64×56 pixels was devised by our laboratory.As the luminance current characteristics of OLED was linear,the constant current driving method was employed to wipe out the cross talk caused by the voltage drops along the columns(ITO anode) of the display.The column driving circuit with constant current sources as well as the row driver were presented in this article.In the PM addressing mode,the matrix-type display was scanned line by line over the frame time.When a line was selected,each pixel in the line was fed with a constant current pulse,constructing the pattern displayed on the OLED matrix.In order to obtain a good image quality,the design of the current source seems very important.This paper describes a current source that uses the transistors and resisters.And this current source relys on feed back techniques to achieve regulation.Some measurements were taken to improve its stability and temperature characteristics correspondingly.Abrief analysis was also made to gain insight into the behavior of the transistors used in the current source.The constant current sources have been proved efficient in several experiments.They are economical,taking a small area and stable,contributing a new idea to improve the PM-OLED driving method.关键词：organic light emitting diode;constant current source;driving circuit;passive matrix122|93|1更新时间：2020-08-11
- 摘要：The flat panel display(FPD) such as FED and PDP have been developed rapidly in recent years.The FPD needs high-voltage driven signal,so the driven circuit must include high-voltage interface.As the development of CMOS technology,high-voltage CMOS devices and low-voltage circuits can be integrated in the same chip,so the cost of the system can be reduced and the reliability of the circuit can be improved.The LDMOS structure was taken as the structure of the high-voltage devices is LDMOS because the fabrication of LDMOS can be compatible with standard CMOS process.Combined with 0.8 μm CMOS technique of IMECAS(Institute of Microelectronics,Chinese Academy of Sciences),the process to fabricate high-voltage CMOS devices is designed by Synopsys TCAD software(Tsuprem-4 and MEDICI).In order to guarantee the validity of simulation results,key technology parameters should be calibrated based on the experimental results.According to the calibrated parameters,the drift region of LDMOS was optimized based on the RESURF technique and the whole process was simulated by TCAD software.The simulated results show that the breakdown voltage of high-voltage NMOS device is 220 V,the threshold voltage and driven ability of HVNMOS are 0.8 Vand 1×10-4A/μm,respectively;the breakdown voltage of highvoltage PMOS device is -135 V,the threshold voltage and driven ability of HVPMOS are -9.7 V and 1.8×10-4A/μm,respectively.The high-voltage CMOSdevices can be used in high-voltage integrated circuit(HV-IC) such as driver ICs for PDPand FED.关键词：display driver;high-voltage CMOS devices;0.8 μm CMOS process;simulation120|222|1更新时间：2020-08-11
- 摘要：One of the important challenges in luminescent material research nowadays is to development of new phosphors under excitation with the vacuum ultraviolet spectral region(VUV,E>50000 cm-1,λ<200 nm).The VUVphosphors used in mercury fluorescent tubes have high quantum efficiencies closing to 100%.Therefore,to make a noble gas discharge fluorescent tube a competitive phosphor with higher quantum efficiencies than100%,i.e.more than one visible photon should be obtained per Absorbed VUV photon.This phenomenon is called quantum cutting.The goal of our research is to find an more efficient visible quantum cutter.In order to achieve this,GdF3:Eu3+ nanocrystals and nanorods were synthesized by micromulsion-mediated hydrothermal process.The structure,shape and particles size were characterized by means of XRD,and TEM.VUV excitation spectra of GdF3:Eu3+ nanocrystals showing that the Gd3+ ion can absorb one VUVphoton and was excited into the 6GJ level,and then the 6GJ level relaxes to transfer the energy to Eu3+ ion by two-step energy decaying processes,yielding two visible photons at room temperature.The visible quantum(efficiency) of GdF3:Eu3+ NCs was calculated to be close to 170% by correlative transition emission peaks(intensity) ratio under VUV excitation at 160 nm.关键词：GdF3：Eu3+;nanocrystal;visible quantum cutting;quantum efficiency111|84|1更新时间：2020-08-11
- 摘要：A Gd-complex,tris-(dibenzoylmethanato)-mono-(bathophenanthroline) gadolinium [Gd(DBM)3bath] was used to tune emission colour in OLEDs.The Gd(DBM)3bath layer was inserted between the hole-transporting layer(m-MTDATA) and electron-transporting layer(TPBI).The ELcolor can be tuned from green at 525 nm to orange at 593 nm by increasing the thickness of Gd-complex layer.When the Gd-complex layer was thin enough,this layer became discontinuous.The discontinuity was increased when the thickness of this layer was further decreased.As a result,the exciplex from m-MTDATA/TPBIwas also formed besides the exciplex from m-MTDATA/Gd-complex.The shifts of spectra were due to the change of proportion for the two exciplexes.These results show that different emission color can be achieved by changing exciplex formation and its intensity in the same device configuration.Asimple technique for tuning the color of OLEDs by controlling the thickness of Gd-complex layer can be demonstrated.Besides,other complexes of trivalent rare earth with(β-diketone) may also play alike roles in such OLEDs.关键词：organic light-emitting diode;gadolinium complex;exciplex128|86|0更新时间：2020-08-11
- 摘要：Organic light-emitting devices(OLEDs),which consist of organic thin films and exhibit light emission under electric current excitation,are expected to be one of the most promising candidates for flat panel display.After Tang reported the efficient double-layer OLEDs,different types of fluorescent materials have been studied and tremendous progress has been made in the past decade.To further improve EL efficiency,the organic phosphorescent materials,which harvest excitation energy of both singlet and triplet states,have been introduced in OLEDs.By employing the phosphorescent materials,the internal quantum efficiency can theoretically reach 100% and emission color can be tuned by modifying the phenylpyridine ligand.The complexes based on Ir(ppy)3 skeleton have such a simple molecular structure and excellent luminescent properties that many efforts are still focusing on chemical modification of this type of complexes for better electrophosphorescent performance.We synthesized a new iridium(Ⅲ) complex,iridium(Ⅲ) bis(2,5-di(4-ethylphenyl)pyridinato-N,C2′)acetylacetonate [(deppy)2Ir(acac)],based on2,5-di(4-ethylphenyl)pyridine ligand.ELdevice was fabricated based on6%(mass fraction) of(deppy)2Ir(acac) doped in CBP.Amaximum luminance efficiency of 23 cd/A and a peak luminance of 10800 cd/m2 were achieved,the device showed green emission corresponding to a maximum wavelength of 548 nm.On the other hand our electrophosphorescent devices show excellent current saturation behavior at higher current density.关键词：iridium(Ⅲ) complex;organic electrophosphorescent material;OLEDs131|85|0更新时间：2020-08-11
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