最新刊期
卷 5 ， 期 1 ， 1984
- 摘要：Using Ar+ laser pumped dye laser with cavity dumper,the time-resolved photoluminescence(PL)spectra and the luminescence decay of GD a-Si:H at 77K have been studied.The time-resolved PL spectra of an a-Si:H film deposited on quartz substrate at TS=127℃ are shown in Fig.1.The shape of the main PL,hand is asymmetrical.In 6600-8900Åregion,the PL decay at different wavelength is shown in Fig.2 and Fig.3.Each PL decay consists of,approximately,a fast exponential decay(t<20ns)followed by slower decay for longer times.The slope of the PL decay curves increases smoothly with decreasing wavelength in 6600-8400Åregion,but does not change in 8400-8900Åregion.According to these results,we suggest that the main PL band of GD a-Si:H is composed of two superimposed PL bands.In the fast decay region,PL band 1(high energy band)and 2(low energy band)have decay time constant τ1 and τ2,respectively.τ1=10ns and τ2=23ns were obtained from the decy cuarves at the two edges of the spectrum assuming that the decay at the edge is mainly determined by only one band.At a given wavelength A and time t,the PL intensity can be expressed aswhere I1(λ,t)and I2(λ,t)are the shape functions of PL band 1 and band 2 Respectively.Since the rate of change of I1(λ,t)and I2(λ,t)with t is much slower in comparison with an exponential function,expression(1)can be approximated byUsing exppression(2),the time-resolved spectra have been analysed from point to point by means of computer and we obtain I1(λ,0)and I2(λ,0),which have approximately Gaussian shape with peaks at 1.73 and 1.58eV,respectively,as shown in Fig.4.The red shift of PL band in a-Si:H is discussed.The results we have obtained show that the red shift of two peaks with time is not large,but the shift of the maximum values of their envelope with time is larger because the decay is faster for band 1(high energy band)than that for band 2(low energy band).These two PL bands may be attributed to the existence of the inho-mogeneous phases(grain like zone and grain boundary like zone)and have been discussed.94|83|0更新时间：2020-08-11
- 摘要：According to Judd-Ofelt theory the intensity parameters of Tm3+ in crystal TmP5O14 were measured.Their values are Ω2=1.50×10-20cm2,Q4=1.5×10-20cm2 and Ω6=0.916×10-20cm2,respectively.The calculated oscillator strengths Pcal.agree with the experimental values Paxp.quite well,the root mean square deviation(rms)is 2.60×10-7.With these Ωλ values,the oscillator strengths,spontaneous radiative transition rates,radiative lifetimes and branching ratios between the excited J manifolds were calculated.The spectral parameters obtained were compared with,those of crytals YAlOs:Tm3+,YAG:Tm3+,Y2O3:Tm3+ and glasses doped with Tm3+ .The summation of intensity parameters(∑τλ=τz +τ4 +τ6)of Tm3+ in crystal TmP5O14 are lower than those of phosphate glass as well as other glasses(borate,germanate and tellurate).∑τλ is a parameter,we found that it is proportional to the oscillator strength P and may be expressed by following equation:P=α∑τλ+b where a and b are two constants obtained from experiments.95|71|0更新时间：2020-08-11
- 摘要：Recently,with the development of the 400-800nm tunable lasers which are made of copper doped inorganic glasses,much attention has been paid to the exploration of the high quality glasses doped with transition metal ions.Hence,copper doped phosphate and fluorophosphate glasses were prepared and the absorption,ESR,fluorescence excitation and life-time measurements were performed in the experiments.It is found that copper exists in the glasses,melted in the reduced atmosphere,mainly as Cu+,and partially as Cun,Cu2+.With the increase of the reduction degree the content of Cu+ increases,while the content of Cu2+ decreases.It can be seen from the ESR measurements that the ESR signal intensities increase with the increase of Cu2+ contents in phosphate glass,and the description of the spectra can be made by using the axial Hamiltonian.The Spin-Hamiltonian parameters are:g//=2.405;g1=2.082;|A//|=105×10-4cm-1,In fluorophosphate glasses,however,no ESR signal could be clearly observed from the ESR measurement though a large enough instrumental gain was set in the experiment.It shews that few cupric ions exist in the glasses,which coincids with our melting condition.There is an absorption band due to Cu2+ ions in phosphate glass,located at around 11000cm-1.It is attributed to the 2E8→2T2g transition of d9 ions in the disordered Oh sites.A strong UV absorption band around 40000cm-1 is attributed to the 3d10→3d94s1 transition of Cu+ ions.It is also a Laport forbbiden transition.A distinct band appears at-16700cm-1 in the spectra of fluorophosphate glass,which may be identified as contribution from the colloid copper.The fluorescence spectra excited at UV range have a broad bandwidth and a large Stokes shift.This shift can simply be explained by using the configurational diagram.However,the site-inhomogeneity of ions in glasses and the effect of the lattice relaxation,we thought,had also been contributed to the shift,based upon the experience in the preceeding studies on the spectral behaviours of transition metal ions doped glasses.The peak positions and bandwidths of fluorescence spectra are 458nm(104nm)for phosphate and 420nm(107nm)for fluorophosphate glass,respectively.From the phosphate to the fluorophosphate glasses the peak positions move toward short wavelength,and the fluorescent intensities and the life-times increase(from 26ns to 60ns).It shows that with the change in glass host the ligand of the oxygen ions is replaced by the ligand of the fluorine ions.The ionic tendency of the bord between the central active ions and the ligands increases.So the coupling between the central active ions and the lattice is relaxed,and the interaction between ions and phonons is weakened.It results in the decrease of the ronradiative transition probability,and in the increase of the quantum efficiency of the luminescence.The results obtained from the excitation spectrum measurements are similar to that from the absorption measurements.The peak positions and bandwidths are 262nm(840A)for phosphate and 247nm(660A)for fluoro-phospate glass,respectively.103|71|0更新时间：2020-08-11
- 摘要：The luminescence of LaOBr:Ce,LaOBr:Ce,Tb and LaOBr:Tb phosphors under UV and cathode ray excitation has been studied.The excitation spectra of Tb3+ ion in LaOBr:Tb consists of a strong broad 4f→5d transition band at 254nm and some weak 4f→4f transition lines in the wavelength range of 300-400nm.The excitation bands of LaOBr:Ce at 352.5,314.5 and 289nm originate from transition between the 4f-ground state(7F)and the 5d-excited state(2D).The excitation spectrum of Tb3+ ion in LaOBr:Ce3+,Tb3+ consists of four bands at 254,289,314.5 and 352.5nm due to Tb3+ and Ce3+.It is clear that only the excitation bard at 254nm belong to Tb3+ ions and the other three bards are the excitation bands of Ce3+ ion.With increasing Ce3+ concentration the intensity of Tb3+ excitation band at 254nm decreases,at the same time the intensities of the Ce3+ excitation bands at 289,314.5 and 352.5nm increase.105|42|0更新时间：2020-08-11
- 摘要：The photoluminescence of the Ce2O3·yAl2O3(where y=12±4)system has been investigated in some detail.The materials were prepared by mixing SP gradeα-A12O3 and Ce oxalate in appropriate ratio ard sintered at 1400~1600℃ under reducing atmosphere for 2~3 hours.It was found,in the range studied,the compounds having Al3+/Ce3+ ratio of about 10~11,showed optimum emission intensity under UV 254nm excitation.However,the ratio of Al3+/Ce3+ has little effept pn the PL emission spectral energy distribution,which peaks all about 454nm,with half height width of 113nm.In order to improve further the luminescence intensity,actions of some fluxes(such as H3BO3,CaF2,LiF,MgO or their combinations)on these materials were studied.It was showed,when these fluxes in the range of 5m/o of the material ,were added respectively to the stoichiometric CeAl11O18 compound,all gave good effect,even if the sintering temperature decreased by 100~200℃.In particular,the materials fluxed with 5m/o H3BO3+5m/0 CaF2 mixture gave an intensity of 21% superior to that of CaWO4:Pb under the same excitation condition.The crystal structures of these phosphors based on this system were determined by means of X-ray powder diffraction method.The principal phase existed in these compounds was identified to be isomorphous with magnetoplumbite,which has a hexagonal ferrite structure with stoichiometric composition CeAl12O195>α=5.561A,c=21.980A,Dx=4.09g/cm2,Z=2.It was also found that there was no continuous solid solution existed,as showed by work [2].This type of material is an efficiently blue-emitting phosphor under UV 254nm excitation,its PL is not so sensitive to contamination that the CP grade,instead of SP grade,raw materials give also satisfactory results.Consequently,the cost of this phosphor may reduce to reasonable level and suitable for large-scale production.These finally make it possible to be used in fluorescent lamp.95|48|0更新时间：2020-08-11
- 摘要：In stationary state the output power of LED can be written aswhere η is the external quantum efficiency,ηi the internal quantum efficiency,ηq,the carrier efficiency,J the injection current density,A,the radiation cross-section and e the electron charge.Using the standard power pB as normalizing treatment,we can obtain the normalized equationwhere I is the injection current,ηi,B and IB is the standard internal quantum efficiency and injection current,respectively.Owing toso we must consider simultanously the influence of the carrier lifetime τ and the radiation lifetime τr.According to the literature.143|56|0更新时间：2020-08-11
- 摘要：The diffusion length of minority carriers in P-Ga(1-x)InxAsyP1-y(x=0.74,y=0.61)grown on InP substrate were determined by measuring the photocurrent under laser scan ard electroluminescent decay of the LED.The carrier concentration of the P-Ga(1-x)InxAsyP1-y,epitaxial layer is 2×1017cm3,while the layer thickness is 2~3nm.The photocurrent response R of the sample was measured as a function of distance(x)from the p-n junction(Fig.4),using a He-Ne laser with a wavelength of 6328A as the scanning light source.R is expressed as a function of the diffusion lengths(Ln),diffusion coefficients(Dn),surface recombination velocities(S)and photoabsorption coefficients(α).Csee Equation(1)]The electroluminescent decay method is somewhat indirect.The diffusion length(L)of the minority carriers is determined through the relation L=(Dτ)1/2,in which D is the known diffusion coefficient ard τ is the decay time of luminescence.The light emitting diodes were prepared with the samples used in the laser scan experiment.It was assumed that trapping lifetime has little influence on electroluminescence decay time.Experimental results of the two methods are ccmtrred in Table 1.The results show good agreement.The two independent experiments were analyzed simultaneously to obtain surface recombination velocity S.S is 6~7×104cm/s.Diffusion length L,is 1.6~2.2μm.Moreover,the behaviour of the minority carrier in P-Ga(1-x)InxAsyP1-yon InP substrate were discussed.89|52|0更新时间：2020-08-11
- 摘要：This paper gives a review on the fabrication,structure,arid electrical characteristics of Langmuir-Blodgett thin films as well as the study of the energy transfer and the photoelectrical transport in them.The possible ap-plicatiosn of this thin film technique are also reviewed.116|68|0更新时间：2020-08-11
- 摘要：A low-duty-cycle triangle pulse current was served as scanning drive current for semiconductor lasers.Consequently,luminescence intensity versus current(L-I)curves of lasers can be exhibited on a dual oscilloscope.From the curves the threshold currents,the emission powers can te directly read,and "kinks" or "no-kinks" in L-I curves can also be directly observed.Due to the no heat-damage characteristics,this metbod is especially useful for measuring chips of diode lasers.108|64|0更新时间：2020-08-11
- 摘要：The behaviour of bismuth in GaP is interesting not only because of the possibility of highly efficient radiative recombination at low temperature,but also the "rich" fine structure of the luminescence spectrum,which has not yet been finally identified.An investigation on the luminescence spectra of GaP grown by epitaxy from Ga-Bi melts containing 10at% Bi has been made.Photoluminescence measurements were performed at temperatures between 4.2K-110K.The samples were excited by the 4880Åline from an argon-ion laser.The excitation power was 140mW.The spectra were taken by using an ASI-50D double grating monochromator with a R106 photo-multiplier.The output signal of the photomultiplier was amplified by a lock-in amplifier and recorded by X-Y recorder.125|57|0更新时间：2020-08-11
- 摘要：The photoluminescence of the Ce2O3·yAl2O3(where y=12±4)system has been investigated in some detail.The materials were prepared by mixing SP gradeα-A12O3 and Ce oxalate in appropriate ratio ard sintered at 1400~1600℃ under reducing atmosphere for 2~3 hours.It was found,in the range studied,the compounds having Al3+/Ce3+ ratio of about 10~11,showed optimum emission intensity under UV 254nm excitation.However,the ratio of Al3+/Ce3+ has little effept pn the PL emission spectral energy distribution,which peaks all about 454nm,with half height width of 113nm.In order to improve further the luminescence intensity,actions of some fluxes(such as H3BO3,CaF2,LiF,MgO or their combinations)on these materials were studied.It was showed,when these fluxes in the range of 5m/o of the material ,were added respectively to the stoichiometric CeAl11O18 compound,all gave good effect,even if the sintering temperature decreased by 100~200℃.In particular,the materials fluxed with 5m/o H3BO3+5m/0 CaF2 mixture gave an intensity of 21% superior to that of CaWO4:Pb under the same excitation condition.The crystal structures of these phosphors based on this system were determined by means of X-ray powder diffraction method.The principal phase existed in these compounds was identified to be isomorphous with magnetoplumbite,which has a hexagonal ferrite structure with stoichiometric composition CeAl12O195>α=5.561A,c=21.980A,Dx=4.09g/cm2,Z=2.It was also found that there was no continuous solid solution existed,as showed by work [2].This type of material is an efficiently blue-emitting phosphor under UV 254nm excitation,its PL is not so sensitive to contamination that the CP grade,instead of SP grade,raw materials give also satisfactory results.Consequently,the cost of this phosphor may reduce to reasonable level and suitable for large-scale production.These finally make it possible to be used in fluorescent lamp.99|22|0更新时间：2020-08-11
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