最新刊期
卷 24 ， 期 3 ， 2003
- 摘要：Spectral hole burning acting as a high resolution spectroscopic technique has potential applications on high density optical storage. The present paper report the research results on inhomogeneous broadening, fluorescence line narrowing, high temperature persistent spectral hole burning, mechanism of hole burning, hole burning dynamics and thermal stability of spectral holes. We designed and prepared new material system of divalent samarium ion doped alkaline earth metal fluoride halides for high temperature hole burning. Room temperature hole burning and spectral hole with longer lifetime were performed. Various local configurations were distinguished by using time resolved spectroscopy. Spectral redistribution induced by hole burning indicates that trivalent samarium ions act as electron traps. Hole burning dynamics was analyzesed by using Block theory.关键词：spectral hole burning;fluorescence line narrowing;homogeneous broadening;inhomogeneous broadening98|148|2更新时间：2020-08-11
- 摘要：On the ground of the study of the luminescence spectral properties, the temperature dependence of the intensity, the decay of the luminescence, and the thermoluminescence of PbWO4 scintillating crystals, combining the results from the theoretical calculations of its electronic structure, a model of the luminescence dynamics of PbWO4 scintillator is suggested with the fundamental band structure, the states of the excitonic luminescence centers, and the position of the trap levels in the band gap defined. According to the theoretical calculations, the band gap is 4.4eV, consistent with the fact that the 265nm excitation band is corresponding to the band transition. The stronger 310nm excitation band originates from the exciton whose binding energy is 0.41eV. The energy difference between the ground state and the excited state is 2.88eV and 2.38eV respectively for blue (430nm) and green (520nm) emission centers. The thermal activation energy for the blue and green emission centers is 0.18eV and 0.13eV respectively calculated from the temperature dependence of the luminescence intensity. The thermoluminescence curves indicate that several types of electronic traps exist in the band gap with the energy depth of 0.42, 0.60, 0.65eV and the deepest 1eV or so. With this dynamical model, the luminescence process of PbWO4 can be fully explained, especially for the causation of the low luminescence efficiency at room temperature because of the strong thermal quenching. On the other hand, according to our study on the luminescence of PbWO4 annealed in different atmosphere, we suggested that the green emission center is "WO42-+Oi"where Oi is oxygen interstitial, instead of "WO3+F" where F is an oxygen vacancy holding two electrons, and the blue emission center is some kind of combination center with the form of "WO42-+some intrinsic defects".关键词：scintillator;PbWO4 crystal;luminescence dynamics;emission center92|104|0更新时间：2020-08-11
- 摘要：A new luminescence material-LaPO4 doped with Eu2+ and Ce3+ was prepared by high temperature solid state reaction. And the optical properties of Eu2+ activated and Ce3+,Eu2+ coactivated lanthanum phosphates were investigated by using photoluminescence(PL) measurements. Emission spectrum of LaPO4:Eu2+ recorded at room temperature with 324nm excitation shows a broad emission band centered at 423nm.And it is possible to determine the distribution of this broad emission band in the spectrum associated with transition from the 4f5d level of Eu2+ ion. The excitation spectrum of Eu2+ activated lanthanum phosphate recorded at room temperature monitoring 423nm emission exhibits absorption in UV region (220～400nm) assigned to the 4f→5d transition of Eu2+ ion. Lanthanum phosphate doped with Ce3+ was also prepared by high temperature solid state reaction. The room temperature photoluminescence spectra of LaPO4:Ce3+ show the broad emission and excitation band of Ce3+ ion,around 342nm and 284nm,respectively. From these spectra above, it's possible to deduce that energy transfer between the Eu2+ and Ce3+ ion will probably happen because of the well overlapping between Ce3+ emission and Eu2+ excitation. And it's well proved in the excitation spectrum of LaPO4 coactivated by Eu2+ and Ce3+ at room temperature, monitoring Eu2+ emission. This spectrum shows a strong absorption band of Ce3+, ranging over 220～340nm, in addition to original f→d transition of Eu2+(220～400nm). That is to say there happens a sensitization of Eu2+ by the presence of Ce3+ ion. The Eu2+ emission intensity of LaPO4:Ce0.013+, Eu0.012+ is 5.6 times higher than that of the corresponding phosphor activated by Eu2+ only. A series of LaPO4:Ce0.013+, Eux2+ were prepared to study the mechanism of the energy transfer between the Eu2+ and Ce3+ ion. The emission spectra of the LaPO4:Ce0.013+, Eux2+ at room temperature were measured. The relationship between the Ce3+ donor emission intensity and the Eu2+ acceptor concentration was fit to the d→d (dipole dipole) energy transfer model for multipole multipole interaction. So it is concluded that the energy transfer between the Ce3+ and Eu2+ ions in lanthanum phosphate is to be a process of dipole dipole resonance interaction.关键词：lanthanum phosphate;luminescence;europium;cerium;energy transfer86|69|3更新时间：2020-08-11
- 摘要：Yttrium aluminates are interesting compounds,in particular with regards to their optical properties.Activation by Ce3+,for example,gives a fast response flying spot scanner phosphor,and activation by Tb3+ gives a characteristic narrow band phosphor suitable for contrast enhanced display applications in high ambient illumination conditions.The YAG based materials are normally synthesized at a relatively high temperature(>1500℃) by a solid state reaction between Al2O3 and Y2O3.Such conditions normally lead to powders of relatively large and wider varying grain sizes and varying impurity content.The sol gel method,because of its apparent advantages of fine homogeneity,high reactivity of starting materials and lower sintering temperature,is a new route to synthesize powders. In this study,the Eu3+ doped YAG phosphors were synthesized by the sol gel process using metal alkoxide at the lower temperature of 1000℃.The formation process and structure of the phosphor powders were investigated by means of TG DSC,XRD.The purified crystalline phase of YAG were obtained at 1000℃.The differences for the excitation and emission spectra of Eu3+ in crystalline and amorphous states of YAG were observed,and the emission intensities increased with the increasing of sintering temperature and Eu3+ concentration.关键词：sol-gel method;Y3Al5O12：Eu3+;luminescence108|260|6更新时间：2020-08-11
- 摘要：With the development of technological and experimental techniques,crystals with all kinds of dimension and shape have been made by experiment, which has brought out a large market for the apply of new materials. So there is continuing interests in polaron. Lee Low Pines calculated the ground state energy of polaron by a variational technique. Huybrechts calculated the energy of the ground state and the first internal excited state of the optical polaron for different values of the electron phonon coupling. N.Tokuda studied the dependence of ground state energy, effective mass and the mean number of polaron on the coupling constant by using the unitary transformation and the method of a lagrange multiplier. Larsen got the ground state energy of the two dimension magnetoplaron by using forth order perturbation theoretic method. Wei et al. investigated the cyclotron resonance mass and frequency of the interface polaron by using Feyman path integration method. Recently, Catandella et al. studied the properties of polaron in one dimension Holstein molecular crystals by using a new variational method, which chosen the linear overlap of Bloch wave of large polaron and small polaron as a trial wavefunction, obtained the variational regularities of the ground state energy, mass and the mean number of polaron with coupling constant. We also did some works on polaron by using Huybrechts' method. But all works were based on only one considering either magnetic field or coupling strength,respectively. This paper is going to illustrate the common influence of magnetic field and coupling strength on the properties of polaron. The variational relations of the ground state energy, self trapping energy and Landau energy with coupling constant and cyclotron resonance frequency are derived by using linear combination operator method. Numerical calculation indicates that the vibration frequency λ firstly falls, arriving to a minimum value, late increases with increasing coupling constant α;λ monotonously rises with increasing cyclotron resonance frequency ω c;the ground state energy E0 decrease with increasing α and monotonous rises with increasing ω c;the self trapping energy E0tr increases with increasing α and ω c;Landau energy E0L firstly increases to a maximum and then fall with increasing α;E0L firstly rises to maximum also and then decreases with increasing ω c.关键词：polaron;ground state;coupling strength;magnetic field strength82|107|0更新时间：2020-08-11
- 摘要：Analytic forms of the linear and the third order nonlinear optical intersubband absorption coefficients are obtained for Morse quantum well using density matrix formalism and iterative method. The numerical results are presented for a typical GaAs/AlGaAs Morse quantum well. The results show that the peak absorption is reduced with the incident optical intensity increasing. The total optical absorption enhances with an increase in the parameter a.关键词：Morse quantum well;optical absorption coefficient;density matrix formalism94|112|3更新时间：2020-08-11
- 摘要：Lower electric field periodic poling of vapor transport equilibration preparing stoichiometric Mg:LiNbO3 crystal is reported for the first time. The coercive field of the crystal was found to be ～1.2kV/mm, only a twentieth of that of the congruent LiNbO3. Homogeneous domain patterns with periods of 6.2～6.4μm was used for the second harmonic generation of green light. A normalized second harmonic generation efficiency 4.8%/W was obtained at room temperature.关键词：stoichiometric Mg:LiNbO3 crystal;second harmonic generation108|119|1更新时间：2020-08-11
- 摘要：As a key pole of an optical computer, optical switches interest many people recently. However, it is difficult to improve the turndown rate of optical switch because of the limit of lifetime of carriers (or excitons). In order to accelerate the decay of excitons, a new type of (CdZnTe,ZnSeTe)/ZnTe complex quantum wells were designed and fabricated via low pressure metal organic chemical vapor deposition method (LP MOCVD). In this complex structure, the ZnSeTe/ZnTe quantum well is a type Ⅱ quantum well. Compared with the adjacent CdZnTe/ZnTe quantum well, the ZnSeTe/ZnTe quantum well has lower n=1 electron level and wider energy gap. So it can accept the carriers tunneled from the CdZnTe/ZnTe quantum well with not affecting the optical nonlinear property of the CdZnTe/ZnTe quantum well. The substrate was GaAs [100]. The widths of layers in CdZnTe/ZnTe/ZnSeTe were 3nm/8nm/9nm, respectively. It was expected that the excitons formed in the CdZnTe/ZnTe well would tunnel into the ZnSeTe/ZnTe well before the recombination. By means of shortening the lifetime of excitons in the CdZnTe well, faster turndown speed will be obtained. Photoluminescence and absorption spectra were employed to characterize the complex quantum wells. Pump probe experiment was done to study the exciton decay in CdZnTe well of the complex structure. Single exponential fitting of the pump probe result yields a down time of 691±79fs, which is shorter than the exciton life time of single CdZnTe quantum wells in some publications. It can be considered that there exists efficient tunneling from CdZnTe well to ZnSeTe well.关键词：(CdZnTe;ZnSeTe)/ZnTe complex quantum wells;exciton decay;pump-probe91|97|0更新时间：2020-08-11
- 摘要：The fundamental physical properties of Hg1-xCdx Te make it an excellent candidate material for infrared photoelectric detectors. Recently, much attention has been paid to Hg1-xCdx Te films grown by different epitaxial techniques on the substrate Cd1-yZny Te due to the possibility of fabricating large area detectors as well as high precision focal plane array detectors. Investigations of the phonon vibration spectra for Hg1-xCdx Te are necessary to understand the lattice dynamics and to obtain structure information about the material. In this paper, the micro Raman and micro photoluminescence spectra of four LPE Hg1-xCdx Te epitaxial film samples were measured at room temperature within the spectral range of 100cm-1 to 5 000cm-1.The micro photoluminescence results show that there is an anion vacancy resonance level far up in the conduction band, about 1.47eV above the conduction band edge of the Hg1-xCdx Te epitaxial films. In the micro Raman spectra of samples there are four main Raman peaks 120, 138, 155 and 261cm-1 are observed. Raman peaks 120cm-1 belongs to HgTe like TO1 phonon vibrational mode, 138cm-1 belongs to HgTe like LO1 phonon vibrational mode, 155cm-1 occurs due to the CdTe like LO1 and CdTe like TO1 phonon mixed vibration, and 261cm-1 comes from the two phonon mode TO1(HgTe like)+LO1(HgTe like). Our results definitely show that the micro photoluminescent structure is mainly due to the improvement in quality of the Hg1-xCdx Te epilayer.关键词：Hg1-xCdxTe epilayers;micro-Raman spectrum;micro-photoluminescence spectrum;LPE100|111|0更新时间：2020-08-11
- 摘要：Organic electroluminescent (OEL) materials have recently attracted much interest due to their intriguing physical properties and potential applications to flat panel display. Blue EL emitter is essential for the development of a full color display based either on the "color changing medium" technology or the RGB filtered white emission. Many blue organic EL materials have been investigated by a number of researchers. Among them, the most promising ones are DSA derivatives. These classes of compounds generally offer many attractive properties such as high thermal stability and good film forming ability, etc. In this paper, the DSA derivative blue emitting material 4,4' bis(2, 2 diphenylvinyl) 1,1' biphenyl, i.e ., DPVBi is synthesized via the Wittig Horner reaction, and determined by IR,1H NMR and elementary analysis. The photoluminescence(PL) of this compound in solid film and EL have been studied. DPVBi is intense blue fluorescent material and have a good film forming ability. The excitation and emission spectra of the vacuum deposited film of DPVBi have been studied. The emission spectrum shows the emission lies in the blue region with a peak at 460nm under the excitation of 360nm light. A blue organic light emitting diode(OLED) with the structure ITO/CuPc/NPB/DPVBi/Alq3/LiF/Al is studied. The EL spectrum of the device is similar to the PL spectrum of single layer DPVBi, indicating that the emission from the device resulted from the same excited state of the DSA derivative. The CIE chromaticity coordinates of the device are x =0.15, y =0.16, showing a very good blue purity. For the blue device, maximum luminance, the luminance under current density of 20mA/cm2 and luminous efficiency are 4373cd/m2, 434cd/m2 and 1.24lm/W, respectively. Particularly, it can be found that the CIE chromaticity coordinates of the device can keep better stability all the time with increasing current density as well as showing a very good blue purity. Because the stability of chromaticity is one of the most important factors to practical application of OLEDs, and DPVBi is a stable blue light emitter, it is suitable for applications to flat panel display.关键词：blue emitting material DPVBi;synthesis;luminescent properties;stability of CIE chromaticity coordinates103|96|7更新时间：2020-08-11
- 摘要：An organic white light electroluminescent device with high performances is designed and fabricated. In this work, the efficiency of blue light emitting was improved only by designing the device structure, which increase the performances of the white light emitting device. Using a hole blocking material (BCP) to controlling the light emitting zone based on NPB layer, we obtained blue light emitting, which comes from excited NPB molecules. Similarly, we obtained yellow light emitting by doping in NPB layer with rubrene. Base on the above, through partly doped NPB layer with rubrene, in which the doped part of NPB layer emits orange light and the undoped part contributes to blue light, we can obtain white light emitting. Because the undoped part of NPB is near the interface of NPB/BCP and this layer is very narrow, only about 3nm, the efficiency of blue light emission is increased, which results the improvement of the performances of white light emitting device. The device has a maximum brightness of 17000cd/m2 (at a driving voltage of 22V), and the maximum electroluminescent and power efficiency are 3.05cd/A and 1.92lm/W (at a drive voltage of 5V, the current density of 0.5mA/cm2), respectively. At drive voltage of 5V, the CIE coordinate of the device is (x =0.317, y =0.328), which is very close to the equi energy point.关键词：organic electroluminescent device;white-light91|112|3更新时间：2020-08-11
- 摘要：Zinc-oxide (ZnO) is an Ⅱ-Ⅵ semiconductor with a wide direct band gap of 3.37eV at room temperature (RT) and a high exciton binding energy of 60meV. Because of this feature, ZnO is a promising candidate for use in ultraviolet wavelengths light emitting devices and lasers. ZnO thin films have been grown on a (400) Si substrate by plasma molecular beam epitaxy (P MBE). Before growth, the Si substrate was chemically cleaned by a standard RCA process and then was thermally treated at 650℃ in ultrahigh vacuum for about 5min. During growth, the Si substrate temperature was at 450℃.The plasma power was kept up 300W. The zinc-flux of purity zinc(6N) source and oxygen(5N) overpressure in the growth chamber were kept at around 4×10-5Pa and 6×10-3Pa, respectively. Obtained thickness of the sample is about 100nm(Sample S1). To improve the crystal quality, the samples were annealed in oxygen for two hours at temperature of 700℃(Sample S2), 800℃(Sample S3), and 900℃(Sample S4), respectively. The ZnO thin films were characterized by X-ray using a rotating anode XRD with CuKα radiation wavelength of 0.154nm. PL spectra were excited by 325nm line of a He Cd laser. The X-ray diffraction spectra show a strong (002) diffraction peak and weaker other orientation peaks of the ZnO thin films. This indicates that the grown samples are polycrystalline structure. The full width at half maximum(FWHM) of S1, S2, S3 and S4 samples are 0.257, 0.244, 0.236, 0.206°, respectively. Above result proves that the crystal quality is improved with increasing annealing temperature. In the PL spectra, an ultraviolet (UV) emission is observed at RT for all samples. In order to verify the origin of this UV emission, temperature dependences of the PL intensities are measured. This UV band at RT comes from the emission of free exciton and radiative recombination of bound exciton associated with one LO phonon, in which bound exciton is considered to be related to deep centers.关键词：ZnO;plasma assisted molecular beam epitaxy (P-MBE);XRD;photoluminescence (PL)85|88|2更新时间：2020-08-11
- 摘要：ZnO is an n-type semiconductor having a hexagonal wurtzite structure. Because its exciton bonding energy is as high as 60meV, ZnO exhibits good piezoelectric, photoelectric and optical properties at room temperature, and might be a good candidate for laser and electroluminescence device. In addition, the melting point of ZnO is high enough to ensure its thermal stability. Since the discovery of the laser of ZnO in ultraviolet light region in 1997, ZnO has become a new hotspot in the research of the ultraviolet light emission material. But for the existence of some native defects in ZnO, generally, ZnO is a n-type semiconductor material. By this time, the research of p type ZnO material still needs more work. According to previous reports, nitrogen is a promising candidate of dopant for the fabrication of p type ZnO, so a lot of researchers make attention of the doping of nitrogen into ZnO. Nitride zinc-oxide thin films were fabricated by rf. sputtering technique, and the concentration of nitrogen in films was changed by a series of annealing process in oxygen ambient in this letter. The annealing temperature is ranged from 300 to 1000℃.After the annealing process, X-ray diffraction spectrum, X-ray photoelectron spectrum, Photoluminescence spectrum and Raman scattering spectrum were used to investigate the change of the crystal structure and the optical properties of the films and the effect of the nitrogen doping was discussed.关键词：nitride zinc-oxide;exciton;annealing process89|109|0更新时间：2020-08-11
- 摘要：We report a simple method for preparing polycrystalline ZnO thin films by thermal oxidation of metallic Zn films, which were prepared by plasma assisted E-beam evaporation.X-ray diffraction (XRD) and photoluminescence (PL) spectra were used to characterize the structural and optical properties of the thin films.XRD indicate that there are ZnO nanoparticles exist in the as-grown Zn film result from O2 plasma oxidation.With the annealing temperatures increasing, the grain sizes gradually increase and the quality of the hexagonal wurtzite structural ZnO thin films are evolution.The photoluminescence spectra show a strong near band edge (NBE) emissions with a weak deep level (DL) emission.Because of the quantum confinement effect and the dispersion of the grain size, the full width at half maximum (FWHM) of the photoluminescence (PL) peaks for the as-grown film is more wide and the PL peak position is shorter than that of the annealed ZnO films.Among samples of annealed ZnO films, the PL intensity of the bound exciton reduces with the increase of the thermal oxidation temperature, which drive UV PL peaks to shorter wavelength.The dependence of PL spectra on temperature from 82K to 300K for ZnO thin film annealed at 600℃ indicates that the bound exciton emission decrease and PL peaks exhibit red shift with the increase of annealing temperature.Peak position of the free-exciton emission is a function of temperature from 82～220K.The theoretical simulation to the experimental data is obtained by using Eq.:E(T)=E(0)- αT2/(T+β).The consequence of the theoretical fit agrees well with the reported value.关键词：plasma-assisted;E-beam evaporation;photoluminescence (PL);thermal oxidation87|80|7更新时间：2020-08-11
- 摘要：ZnO film is of great interest for short-wavelength optoelectronic application because ZnO semiconductor with a wide band gap of 3.34eV has a large exciton binding energy of 60meV at room temperature. At present,there have been many different techniques used to prepare nanocrystalline ZnO films such as molecular beam epitaxy,vapor phase deposition,and pulsed laser deposition.In this paper nanocrystalline ZnO films have been grown by a simple method of cathodic electrodeposition. Preparation of ZnO films using this method presents several advantages such as relatively high deposition rate,low deposition temperature,and low equipment cost. Cathodic electrodeposition has been widely used to deposit ZnO micrometer size particles,while little has been reported on the deposition of ZnO nanoparticles by cathodic electrodepo sition on Si substrate. In this paper dimethylsulfoxide (DMSO) solutions containing ZnCl2 is introduced to get OH free ZnO films. Furthermore Si wafers were used as the substrates,which is of considerable interest to the optoelectronic integration. Deposition is carried out in DMSO solutions containing ZnCl2 with different concentration from 0.01mol/L to 0.05mol/L on Si substrates at room temperature. The grown films were characterized by means of ex situ techniques:X-ray diffraction,atom force microscopy,infrared spectroscopy and photoluminescence spectroscopy. The effects of ZnCl2 concentration on the structural and optical properties of the films have been studied. The mean grain size of the samples,which increases with the increase of ZnCl2 concentration are 9.8, 10.4 and 14.5nm,respectively. The photoluminescence spectra of all the samples show two distinct features:strong ultraviolet emission lines from ZnO free exciton and negligibly weak green emission band around 510nm,which is from deep level defect emission associated with oxygen vacancies in the ZnO lattice.The exciton emission dominated in the photoluminescence spectra. In conclusion,nanocrystalline ZnO films have been fabricated by cathodic electrodeposition on Si substrates from DMSO ZnCl2 electrolytes. The results indicate that this method is a promising way to prepare nanocrystalline ZnO films.关键词：ZnO;nanocrystalline films;cathodic electrodeposition97|81|7更新时间：2020-08-11
- 摘要：In order to widen the tunable range, the PL spectra of C102 and RH6G in the ethanol solution with different concentration and in embedded films-porous alumina were studied. C102 and RH6G are good dye in the dye family, they are characterized by wide tunable range and fine physical and chemical quality. The carrier anodic porous alumina is transparent in the range of visible light and that it will not disturb the absorption of dye. Commonly, the dye with shorter wavelength absorption and emission spectrum was named as donor, and the dye with longer wavelength absorption and emission spectrum was named as acceptor. It was known that if the fluorescence spectrum of the donor overlapped with the absorption spectrum of the acceptor, the donor would deliver part of its energy to the acceptor, and the acceptor would luminescence because of excitation. Anodization was conducted at a constant voltage condition using a DC stabilized power and flow supply and the specimens were prepared and measured in the ambient air. In this experiment, C102 was donor and RH6G was acceptor. It was found that the fluorescence spectrum of C102 and the absorption spectrum of RH6G overlapped in a certain range, so if they were mixed according to a definite proportion, the spectra would be expanded comparatively to any one of these two dyes. Keeping the concentration of the donor constant and altering that of the acceptor, the author found that, along with the increasing of the acceptor's concentration, the donor's fluorescence spectra shifted to shorter wavelength (blue shift), while the fluorescence of the acceptor shifted to longer wavelength (red shift). The trend of intensity alteration was that the intensity of donor changed from a degree far exceeding that of the acceptor to the degree almost equal to that of the acceptor and at last, the intensity of the acceptor exceeded that of the donor, when the intensity of acceptor was nearly equal to zero. All these suggested that energy transfer existed between donor and acceptor. The enhancement of acceptor PL intensity was at the cost of the weakening of donor PL intensity. Donor strengthened the efficiency of energy transfer while the concentration of acceptor increased. Compared with the fluorescence spectra in anodic porous alumina, it was found that the fluorescence spectra range of these two dye mixed together was wider evidently than that of one, and the trend of variation was similar to that in the ethanol solution. At last, the fluorescence spectra in ethanol solution and in anodic porous alumina were also compared. By this experiment, it was found that porous alumina perhaps was good medium in the development of solid tunable lasers.关键词：porous alumina;PL spectra;giver;receptor84|93|0更新时间：2020-08-11
- 摘要：Semiconducting silicon is the dominant material in microeletronics, which is a key for high technology, but it cannot emit light efficiently. It is necessary to develop Si based light emitting material for optoelectronic integrational device.The study of Si based light emitting materials is a new leading field in semiconductor optoelectronics and photonics. Bulk Si, however, is of little use for photonic devices owing to its indirect band gap and its poor radiative electron hole recombination.The light emitting of Si based quantum dot is attractive research direction. The nc-Si(Si quantum-dot)/SiO2 is a promising light emitting material. The quantum confinement effect in nanocrystallites has proved to be highly effective for light emission. In this paper, the tetraethoxysilane (TEOS) precursor is hydrolyzed with ethanol as co solvent under various concentrations of hydrochloric acid catalyzer to prepare the SiO2 solution through sol gel process.A nc-Si/SiO2 film were fabricated by spin coating of such pre polymer solutions onto glass slides followed by aging and during of resultant gels. We give the SEM(scan-electronics microscope) of nc-Si/SiO2 and energy spectra of nc-Si/SiO2.The effects of colloid viscosity, acid catalyzer concentrations, speed and time of spin coating on quality of film are revealed.In nc-Si/SiO2 film, the particles (nc-Si) in nanocrystalline material have the size of about 1nm to 100nm, and there are several new effects upon conventional material among them e.g. micro-sized effect, quantum-size effect and macro quantum tunneling effect. It is just because of the existence of these effects nanocrystalline material shows out different characteristics on mechanics, thermodynamics, electricity and chemistry. So from the moment of its appearance, nanocrystalline material had been attracting more and more attentions of scientists on it.关键词：Si-based OEIC;sol-gel method;energy spectrum85|60|2更新时间：2020-08-11
- 摘要：The development of polycrystalline silicon thin film on low cost substrates for solar cells is showing an urgent need to reduce cost. In order to achieve high quality, large grains silicon films, high temperature processes have to be used. So the substrates must be high temperature resistant, and fulfill requirements concerning thermal expansion, chemical and mechanical stability. Up to now, silicon based materials are the best choice to satisfy the requirements mentioned above. In this paper, low cost SSP substrates are chosen for our thin film solar cells. SSP substrates are manufactured by melting silicon powder by Fraunhofer institute of solar energy system, Germany. Two kinds SSP substrates, made from high purity silicon powder and from homemade low purity silicon powder, are used in our experiments. The morphology of SSP substrates were measured by using SEM.It can be seen that either made from high purity silicon powder or from homemade low purity powder has very rough surface. The average grain size is about 50～100μm. AES and ICPAES reveal that there are O, B, Fe, Mn and Cr impurity in the low purity SSP substrates and the concentration of Fe and Cr exceed 1017cm-3.High purity SSP substrates have 3%～4% oxygen also. The cell's fabrication processes include:substrate treatments; epitaxy of polycrystalline silicon thin film using rapid thermal chemical vapor deposition (RTCVD); emitter formation; front and rear contacts fabricating; anti reflection coating (ARC) deposition. The resistivity characteristics of the epitaxial thin film was 0.1Ω·cm. Hall mobility is 20～70cm2/V·s.Film thickness is 20～50μm and average grain size are 50～100μm.The largest growth rate is 5μm/min. The best thin film solar cell's conversion efficiency of 6.36% and 4.5% (AM1.5, 25℃, 1cm2) have been achieved on high and low purity substrate. These results show that low cost thin film solar cells have great potentialities. Although anti reflect coating (ARC) fabrication improves cells' performance obviously (cell's efficiency increases 14%～22% with SiN), PC1D calculation shows that the best ARC can increase cell's efficiency 40%, that means our cell's ARC is not optimized. Additionally, the cell's efficiencies increases 4%(some results reach 10%～15%) after 30 minutes forming gas annealing in low temperature. That contributes to reduction of contact resistance and partial passivation of grain boundaries and defects. In conclusion, the polycrystalline silicon thin film solar cells on SSP substrates shows a potential way to reduce the cost of solar cells. Further research will be done in our laboratory.关键词：crystalline silicon;thin film;solar cells112|215|0更新时间：2020-08-11
- 摘要：The CNx films were grown on Si(001) substrates using r.f. magnetron sputtering pyrolytic graphite in pure N2. During the deposition, substrate temperature is kept a constant of 350℃ (Ts). The r.f. power and PN2 were fixed at 300W and 0.5Pa, respectively. Only substrate bias (Vb) is varied from 0V to -150V.The effect of substrate bias on adhesion and roughness of CNx film is discussed. The optimized condition for growing CNx films with the smooth and good adhesion on Si (001) is desired. Atomic force microscopy (AFM) is used to characterize the surface morphology and roughness of the CNx films deposited on the Si (001) substrate. The scratch test was utilized for measurement of coating adhesion of the CNx films on Si (001). The AFM and scratch test results show that the adhesion and roughness of CNx films on Si (001) are highly dependent on substrate bias. It can be found that increased substrate bias causes a rougher surface of CNx films, and correspondingly the minimum value of rms roughness (0.8nm) was obtained while substrate bias increase up to -100V.But when substrate bias increases continuously from -100V to -150V, the rms roughness of the films is enhanced. It is similar to the change of adhesion of the films with substrate bias. The films grown at Vb=-100V obtain better adhesion to Si substrate than that grown at other substrate bias value. The change trend of roughness and adhesion of films with substrate bias is related to the ion energy reaching to the film surface during deposition. It can be concluded that the adhesion and smoothness of CNx films are highly dependent on the energy of the ions reaching on the surface of the films, whereas substrate bias can control this energy, consequently determine the final quality of the deposited films. Thus an appropriate substrate bias is favorable to deposit good quality films by controlling properly the ion energy reaching on the surface of the films. For the deposition of CNx films at Ts=350℃ using r.f. magnetron sputtering, Vb=-100V is optimal condition for obtaining the quite smooth CNx thin films with good adhesion on Si (001) substrate.关键词：CNx films;roughness;adhesion;substrate bias118|238|6更新时间：2020-08-11
- 摘要：Vacuum microelectronics has attracted many research fields in electron beam devices due to high potential in their applications, such as field emission display, high frequency and high power devices, etc. An essential requirement among these devices is the development of a noble cathode which produces a stable, high density and uniform electron emission at low driving voltage. Diamond and related materials are the strong candidates as the cathode materials, because the relatively high brightness of field emission from diamond and diamond like carbon films have been observed at low field by the nitrogen doping and some surface treatment of the films, even though its emission mechanism is not clear. Some emission model had been suggested, however, further investigation to understand the emission mechanism of the materials is essential to develop a flat cathode for actual applications to FED and other vacuum microelectronic devices. The paper describes the fabrication of a plane cathode by plating a thin metal film on polycrystalline diamond film and forming a gated cathode with a planar diode structure. It shows an electron emission from the cathode at driving voltage as low as 10V, and the emanative angle of the emitted electrons is smaller than 6° observed from its image on fluorescent screen. In addition, the field emission from a high quality diamond particle shows hardly emissive due to a high barrier height at the interface between the diamond and the substrate which prevents electron injection into the diamond. The emission mechanism was discussed and suggested that the electron emission occurs probably from grain boundaries in a polycrystalline diamond film.关键词：diamond films;field emission;low driving voltage;planner field emission95|92|1更新时间：2020-08-11
- 摘要：Diamond possesses a low or negative electron affinity surface that allows its surface to emit electrons under low electric field, so diamond films have potential applications in the areas such as field emission display. Although a considerable research effort on diamond field emission has been made in the past few years, the influences of crystal texture of diamond films on emission properties are not yet completely understood. In this article, the effect of seed crystal density on the hot film chemical vapor deposition (HFCVD) diamond film's component, crystal texture and field emission property was analyzed. In most cases, the silicon substrate was eroded or rubbed before HFCVD diamond film. In this report, diamond seed crystals were deposited to silicon substrates with different density by controlling the electrophoresis deposition (EPD) time, then synthesized diamond film on the seeded silicon substrates with a HFCVD reactor.The samples were analyzed with scanning electron microscope (SEM) and Raman spectrum, and the field emission properties of those samples were tested. The result shows that the amount of graphite phase with sp2 bond structure at diamond crystal interfaces is a virtual factor for its electron emission abi lity. A little of the graphite phase is good for the electron transmission in the film, however the amount should not be too much. The high density and small size of the diamond powder on the film surface are helpful to exert the electron emission property. Also the interface resistance of diamond and silicon substrate should be low, ensure the electron inject to diamond film from silicon substrate easily. For the diamond films chemistry vapor deposited on the silicon substrates seeded with diamond powders by EPD process, the area rate of amorphous carbon component and the graphite phase component in the Raman spectrum should be around 1:0.31, which corresponds a better field emission property.关键词：diamond film;field emission;seed crystal density;electrophoresis82|175|2更新时间：2020-08-11
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