闭管热氧化法生长GaAs自体氧化膜的AES和XPS分析

本文首次利用AES和XPS分析了闭管热氧化法生长GaAs自体氧化膜及其界面组成,其主要成分是Ga2O3和元素As,少量的As2O3分布在氧化层的外侧,从而推断出As2O3是本反应的氧化剂。     

透射式GaAs光电阴极组件在真空烘烤后表面氧化的XPS分析

介绍了GaAs光电阴极在高温烘烤后不同深度上Ga原子和As原子氧化的XPS分析结果,并对GaAs中的Ga原子比As原子更容易氧化以及GaAs光电阴极在经过高温烘烤后,其激活所能达到的阴极灵敏度偏低的现象进行了分析.     

生长条件对Ga掺杂ZnO薄膜微观结构及光致发光性能的影响

利用热氧化法在不同参数条件下生长了Ga掺杂范围较宽的ZnO薄膜, 研究了ZnO薄膜的表面微观结构和光致发光性能. 研究表明: Ga以Ga³⁺存在并掺入ZnO晶格取代Zn²⁺, Ga的掺入改变了ZnO薄膜中的缺陷类型及浓度、化学计量比、薄膜表面结晶质量, 进而影响了薄膜的光致发光性能. 随着热氧化温度升高, Ga掺杂量增大, ZnO薄膜的晶粒尺寸增大, 尺寸更均一, 紫外光与可见光强度比增大. 随着热氧化时间延长, Ga掺杂量降低, ZnO薄膜的晶粒尺寸均一性变差, 紫外光与可见光强度比减小.     

Co/S钝化GaAs(100)界面形成的SRPES研究

利用同步辐射光电发射谱研究了Co与CH\-3CSNH\-2处理的S钝化GaAs(100)的界面形成.发现 其界面反应较弱,Co覆盖层达到0.8nm时,形成稳定的界面.GaAs表面上和S原子形成桥 键的Ga原子与Co发生交换反应并扩散到覆盖层中,形成Co—S键.Co覆盖层表面无偏析As的出现,与Co/GaAs(100)界面不同,这表明GaAs表面的S钝化可有效地阻止As原子向覆盖层的扩散. 关键词：     

GaAs表面硫化学钝化,CH3CSNH2处理新探

应用同步辐射光电子谱（SRPES）和光致荧光（PL）方法探讨不同钝化条件对GaAs表面键合状态和电子态的影响．发现无论在酸性溶液或碱性溶液条件下，经过CH₃CSNH₂处理的GaAs表面S都与Ga和As成键，形成硫化物钝化层；钝化层形成后，PL谱的强度明显增强，表明GaAs表面复合中心的减少和缺陷态密度的降低 关键词：     

CH_3OH在Ga-rich GaAs(001)-(4×2)表面上的吸附与解离:团簇模型的密度泛函计算

采用简单团簇模型结合密度泛函理论研究了CH3OH在Ga-rich Ga As(001)-(4×2)表面上的吸附与解离过程.计算结果表明,CH3OH在Ga-rich Ga As(001)-(4×2)表面上首先会形成两种化学吸附状态,然后CH3OH经解离生成CH3O自由基和H原子吸附在表面不同位置上.通过比较各个吸附解离路径,发现解离后的H原子相对更容易吸附在位于表面第二层紧邻的As原子上.     

Al/GaAs界面反应的XPS研究

用XPS研究了清洁无序GaAs表面沉积超薄Al膜后的界面反应,结果表明,原沉积于GaAs表面的Al能进入GaAs衬底取代Ga形成AlAs,而通过Al-Ga替位反应释放出来的Ga则残留在衬底表面,提出了Ga/AlAs+GaAs/GaAs三层结构模型。 关键词：     

氧化镓薄膜的制备及其日盲紫外探测性能研究

采用射频磁控溅射方法在蓝宝石单晶衬底上沉积氧化镓(Ga2O3)薄膜,并通过光刻剥离工艺(Lift-off)制备了金属-半导体-金属结构的Ga2O3日盲紫外探测器。对不同温度下沉积的Ga2O3薄膜分析表明,在800℃下获得的薄膜结晶质量最好,薄膜的导电性则随着沉积温度的上升先增大后减小。在800℃制备的β-Ga2O3薄膜的可见光透光率大于90%,光学吸收边在255 nm附近。在10 V偏压下,探测器的暗电流约为1n A,光电流达800 n A,对紫外光响应迅速。器件的响应度达到0.3 A/W,260 nm波长处的响应度是290 nm波长对应响应度的40倍,可实现日盲紫外波段的探测。     

薄膜厚度对射频磁控溅射β-Ga2O3薄膜光电性能的影响

本文在室温下利用射频磁控溅射技术在(001)蓝宝石衬底上制备了不同厚度的β-Ga₂O₃薄膜,随后将其置于氩气气氛中800℃退火1 h.利用XRD,SEM,UV-Vis分光光度计、PL光致发光光谱仪和Keithley 4200-SCS半导体表征系统等考察薄膜厚度对所得氧化镓薄膜相组成、表面形貌、光学性能以及光电探测性能的影响.结果表明,随着薄膜厚度的增加,薄膜结晶质量提高,840 nm薄膜最佳,1050 nm薄膜结晶质量略有降低.不同厚度β-Ga₂O₃薄膜在波长200—300 nm日盲区域内均具有明显的紫外光吸收,禁带宽度随着薄膜厚度的增加而增加.PL谱中各发光峰峰强随着薄膜厚度的增加而减小,表明氧空位及其相关缺陷受到抑制.在β-Ga₂O₃薄膜基础上制备出日盲紫外光电探测器的探测性能(光暗电流比,响应度,探测率,外量子效率)也随薄膜厚度的增加呈先增后减的趋势.厚度约为840 nm的β-Ga₂O₃紫外光电探测器,在5...     

CH_3CSNH_2钝化对铁磁金属与GaAs界面扩散的影响

通过实验对比 ,研究了CH3CSNH2 钝化对铁磁金属与GaAs界面处As扩散行为的影响 .发现S钝化处理改变了表面As元素的化学环境 ,减弱了As元素向铁磁金属外延层中的扩散现象 ,削弱了As与铁磁金属的反应 ,形成了较窄的反应层 ,并且改善了界面磁性 .初步探讨了S钝化影响As扩散的原因 .     

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.