脉冲激光沉积法(PLD)生长Co掺杂ZnO薄膜及其磁学性能

采用脉冲激光沉积(PLD)法在单晶Si(100)及石英衬底上生长Co掺杂ZnO薄膜,并且比较了不同生长条件下薄膜的性能。实验观察到了700℃、0.02Pa氧压气氛下生长的Co掺杂ZnO薄膜显示室温磁滞回线。采用XRD、SEM等手段对Co掺杂ZnO薄膜的晶体结构及微观形貌进行了分析,得到的ZnO薄膜具有高度的c轴择优取向,结构比较致密,表面平整度较高,并且没有发现Co的相关分相,初步表明Co有效地掺入了ZnO的晶格当中。霍尔测试表明Co掺杂ZnO薄膜样品保持了半导体的电学性能,电阻率为0.04Ω·cm左右,载流子浓度约为1018/cm3,迁移率都在18.7cm2/V·s以上。实验结果表明材料保持了ZnO半导体的性能,并具有室温铁磁性。     

磁控溅射制备ZnO薄膜的受激发射特性的研究

用射频磁控反应溅射法在二氧化硅衬底上制备ZnO薄膜。得到了在不同温度下ZnO薄膜的吸收与光致发光。观测到了纵光学波 (LO)声子吸收峰与自由激子吸收峰 ;室温 (30 0K)下 ,PL谱中仅有自由激子发光峰。这些结果证实了ZnO薄膜具有较高的质量。探讨了变温ZnO薄膜的发光特性。研究了ZnO薄膜的受激发射特性。     

射频磁控溅射ZnO薄膜的结构和光学特性

采用射频（RF）反应磁控溅射法在n-Si(001)衬底上外延生长ZnO薄膜。XRD谱测量显示出较强的（002）衍射峰，表明ZnO薄膜为c轴择优取向生长的。室温PL谱测量观察到了较强的紫外光发射和深能级发射。     

Ag掺杂p型ZnO薄膜及其光电性能研究

采用超声喷雾热分解法在石英衬底上以醋酸锌水溶液为前驱体,以硝酸银水溶液为Ag掺杂源生长了Ag掺杂ZnO(ZnO：Ag)薄膜.研究了衬底温度对所得ZnO：Ag薄膜的晶体结构、电学和光学性质的影响规律.所得ZnO：Ag薄膜结构良好,在室温光致发光谱中检测到很强的近带边紫外发光峰,透射光谱中观测到非常陡峭的紫外吸收截止边和较高的可见光区透过率,表明薄膜具有较高的晶体质量与较好的光学特性.霍尔效应测试表明,在500℃下获得了p型导电的ZnO：Ag薄膜,载流子浓度为5.30×10¹⁵cm关键词： ZnO：Ag薄膜 p型掺杂 超声喷雾热分解 霍尔效应     

MBE生长ZnO薄膜的结构和光学特性的研究

用等离子体源辅助分子束外延(P-MBE)方法在蓝宝石(0001)面上生长出了高质量的ZnO薄膜,并对其结构和发光特性进行了研究。在XRD中只观察到ZnO薄膜的(0002)衍射峰,其半高宽(FWHM)值为0.18°;而在共振Raman散射光谱中观测到1LO(579 cm-1 )和2LO(1 152 cm-1 )两个峰位,这些结果表明ZnO薄膜具有单一c轴取向和高质量的纤维锌矿晶体结构。在吸收光谱中观测到自由激子吸收和激子-LO声子吸收峰,这表明在ZnO薄膜中激子稳定的存在于室温,并且两峰之间能量间隔为71.2 meV,与文献上报道的ZnO纵向光学声子能量(71 meV)相符。室温下在光致发光光谱(PL)中仅观测到位于376 nm处的自由激子发光峰,而没有观测到与缺陷相关的深能级发射峰,表明ZnO薄膜具有较高的质量和低的缺陷密度。     

常压MOCVD生长ZnO薄膜及其性质

用常压MOCVD在蓝宝石 (0 0 0 1)面上生长了氧化锌 (ZnO)薄膜。用AFM、室温PL谱、Hall测量、X射线双晶衍射、卢瑟福背散射 /沟道技术等分析方法研究了样品的表面形貌、结构性能、发光性能和电学性能。AFM分析结果显示 ,薄膜呈六角柱状结晶 ,表面平整 ,粗糙度 (RMS)为 6 .2 5 7nm ,平均晶粒直径达 1.895 μm。室温PL测量该样品在 380nm处有很强的近带边发射 ,半峰全宽为 15nm。使用Hall测量检查了薄膜的电学性质。室温下该样品的载流子浓度为 2× 10 17cm-3 ,迁移率为 75cm2 ·V-1·s-1。用X射线双晶衍射和卢瑟福背散射 /沟道效应研究了薄膜的结晶质量 ,样品的双晶衍射ω扫描半峰全宽为 0 .0 4° ,沟道效应的最小产额比χmin为 3.1%。     

脉冲激光沉积(PLD)法生长高质量ZnO薄膜及其发光性能

采用脉冲激光沉积(PLD)法在单晶Si(100)衬底上生长ZnO薄膜,以X射线衍射(XRD)、原子力显微镜(AFM)和透射电镜(TEM)等手段分析了所得ZnO薄膜的晶体结构和微观形貌。优化工艺(700℃,20Pa)下生长的ZnO薄膜呈c轴高度择优取向,柱状晶垂直衬底表面生长,结构致密均匀。室温光致发光(PL)谱分析结果表明,随着薄膜生长时O₂分压的增大,近带边紫外发光峰与深能级发光峰之比显著增强,表明薄膜的结晶性能和化学计量比都有了很大的改善。O₂分压为20Pa时所生长的ZnO薄膜具有较理想的化学计量比和较高的光学质量。     

低温缓冲层对氧化锌薄膜质量的影响

利用金属有机化学气相沉积(MOCVD)法,在Si衬底上外延生长ZnO薄膜。为了改善氧化锌薄膜的质量,首先在Si衬底上生长低温ZnO缓冲层,然后再生长高质量的ZnO薄膜。通过XRD、SEM、光致发光(PL)光谱的实验研究,发现低温ZnO缓冲层可有效降低ZnO薄膜和Si衬底之间的晶格失配以及因热膨胀系数不同引起的晶格畸变。利用低温缓冲层生长的ZnO薄膜的(002)面衍射峰的强度要比直接在Si上生长的ZnO薄膜样品的高,并且衍射峰的半高宽也由0.21°减小到0.18°,同时有低温缓冲层的样品室温下的光致发光峰也有了明显的增高。这说明利用低温缓冲层生长的ZnO薄膜的结晶质量和光学性质都得到了明显改善。     

MOCVD法生长ZnO薄膜的结构及光学特性

采用MOCVD方法在c Al2 O3衬底上生长出了具有单一c轴取向的ZnO薄膜 ,采用X射线衍射 (XRD)、Raman散射、X射线光电子能谱 (XPS)及光致发光 (PL)谱等方法对ZnO薄膜的结构及光学特性进行分析测试。XRD分析只观察到ZnO薄膜 (0 0 0 2 )衍射峰 ,其FWHM数值为 0 1 84°。Raman散射谱中 ,4 35 32cm- 1 处喇曼峰为ZnO的E2 (high)振动模 ,A1 (LO)振动模位于 5 75 32cm- 1 处。XPS分析表明 :ZnO薄膜表面易吸附游离态氧 ,刻蚀后ZnO薄膜O1s光电子能谱峰位于 5 30 2eV ,更接近Zn—O键中O1s电子结合能 (5 30 4eV)。PL谱中 ,在3 2 8eV处观察到了自由激子发射峰 ,而深能级跃迁峰位于 2 5 5eV ,二者峰强比值为 4 0∶1 ,表明生长的ZnO薄膜具有较高的光学质量     

阴极电沉积ZnO薄膜的取向控制生长

采用阴极电沉积法,在Zn(NO3)2水溶液中,以304不锈钢为衬底制备了ZnO薄膜,研究了Zn2+浓度和电流密度对ZnO薄膜择优取向的影响规律。XRD结果表明:随着Zn2+浓度和电流密度增大,ZnO薄膜逐渐由(002)面择优取向生长转变为(101)面择优取向生长;当Zn2+浓度为0.005mol.L-1、电流密度为2.0mA.cm-2或Zn2+浓度为0.05mol.L-1、电流密度为0.5mA.cm-2时,可以得到(002)面择优取向生长的ZnO薄膜;当Zn2+浓度为0.05mol.L-1、电流密度为2.0mA.cm-2时,可以得到(101)面择优取向生长的ZnO薄膜。根据二维晶核理论,通过分析不同生长条件下的过饱和度及其对ZnO的(002)型和(101)型二维晶核形核活化能的影响,对这一规律进行了解释。可见,通过改变Zn2+浓度和电流密度能够实现阴极电沉积ZnO薄膜的取向可控生长。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.