GaAs极化电子源激活的yo-yo过程研究

通过对GaAs晶体产生极化电子束流的实验过程研究，着重对yo-yo过程中不同的实验参数对产生极化束流以及束流稳定情况的影响进行了分析，为获得稳定而持久的极化电流提供了有力的实验支持，并讨论了极化电流强度的可控性.     

GaAs极化电子源实验研究

对GaAs极化电子源中GaAs晶片的激活过程进行了实验研究，着重采用2种不同的激活过程摸索了实验过程中的相关物理参量，以达到最佳的激活状态，并获得了一些有意义的实验结果.     

NEA GaAs光电阴极激活工艺研究

本文报道了 GaAs 反射式光电阴极的激活工艺过程和结果.通过实验确定了 GaAs表面的热清洁温度,利用钼丝热辐射加热方法达到了比较理想的清洁效果,采用铯分子源和高纯氧作氧源获得了高于1000μA/1m 的激活积分灵敏度.     

改进"yo-yo"Cs/O交替激活方法对GaAs光阴极稳定性影响

为提高激活后GaAs光阴极的稳定性,延长微光夜视器件的工作寿命,围绕Cs/O激活方法和衰减特性进行实验研究.通过对比传统"yo-yo"激活法和改进"yo-yo"激活法在Cs/O激活光电流、光谱响应以及光照衰减方面的差异,发现采用改进"yo-yo"激活法的GaAs光阴极光谱灵敏度更高且稳定性更好.利用四极质谱仪监测真空腔...     

本征GaAs中电子自旋极化对电子复合动力学的影响研究

采用时间分辨圆偏振光和线偏振光抽运-探测光谱,研究了9.6 K温度下本征GaAs中自旋极化电子与非极化电子的复合动力学及其随光子能量演化.发现自旋极化对电子复合动力学具有显著影响.仅在导带底附近测量时,两种方法测试到的复合寿命一致,而在高过超能量电子态测量时,两种方法测试到的复合寿命不一致.指出时间分辨法拉第光谱中,用于反演求解电子自旋相干寿命的电子复合寿命应该使用圆偏振光抽运-探测获得的复合寿命,而不是线偏振光抽运-探测获得的寿命.理论计算与实验结果吻合较好. 关键词： 圆偏振光抽运-探测光谱 自旋量子拍 自旋极化 GaAs     

极化电子源的原理及实验研究

简单介绍了极化电子束的获得,即极化电子源,讨论了对电子束极化度的测量,极化电子与原子散射,以及极化电子束在固物理、生物物理、核物理与粒子物理中的应用． The getting of polarized electrons was briefly introduced, that is the source of polarized electrons. The measurement of polarization in future, the application of polarized electrons in atomic and molecular physics, condensed physics, biological physics, nuclear and particle physics were discussed.     

BEPC束流极化与极化仪的研究

简要介绍了在北京正负电子对撞机(BEPC)上实现束流极化的必要性与可能性,以及束流极化度测量的原理与方法,还简要描述了利用一条同步辐射管道测量BEPC电子束流极化度的测试系统方案设计以及正在开展的实验工作.     

GaAs薄膜的有效量子限制长度及其极化子特性

本文用分数维方法研究Al_xGa_1-xAs衬底上GaAs薄膜中的极化子特性, 提出了确定GaAs薄膜的有效量子限制长度的一个新方法, 解决了原来方法中在衬底势垒处有效量子限制长度发散的困难, 得到了Al_xGa_1-xAs衬底上GaAs薄膜中的极化子的维数和结合能. 关键词： 分数维方法 极化子 GaAs薄膜     

分数维方法研究GaAs薄膜中的极化子

本文采用分数维方法, 在讨论Al_0.3Ga_0.7As衬底上GaAs薄膜的分数维基础上, 计算了GaAs薄膜中的极化子结合能和有效质量. 随着薄膜厚度的增加, 极化子结合能和质量变化单调地减小. 当薄膜厚度L_w<70 Å并且衬底厚度L_b<200 Å时, 衬底厚度的变化对薄膜中极化子的结合能和质量变化的影响比较显著, 随着衬底厚度的增加, 薄膜中极化子的结合能和质量变化逐渐变大; 当薄膜厚度L_w>70 Å或者衬底厚度L_b>200 Å时, 衬底厚度的变化对薄膜中极化子的结合能和质量变化的影响不显著. 研究结果为GaAs薄膜电子和光电子器件的研究和应用提供参考. 关键词： 分数维方法 GaAs薄膜 极化子 低维异质结构     

BEPC束流极化与极化仪的研究

简要介绍了在北京正负电子对撞机（ＢＥＰＣ）上实现束流极化的必要性与可能性，以及束流极化度测量的原理与方法，还简要描述了利用一条同步辐射管道测量ＢＥＰＣ电子束流极化度的测试系统方案设计以及正在开展的实验工作。     

Experimental study on the activation process of GaAs spin—polarized electron source

GaAs spin-polarized electron source is a new kind of electron source, where the GaAs semiconductor crystal is used as a photocathode under the irradiation of helicity light. In this paper the activation process of the GaAs spin-polarized electron source is unvestigated experimentally in detail, during which the negative electron affinity of the photo cathode should be achieved more carefully by absorbing the caesium and oxygen on the surface of the GaAs crystal under ultrahigh vacuum conditions. Besides the different activation processes, the important physical parameters are studied to achieve the optimum activation results. At the same time the stability and lifetime of the polarized electron beam are explored for future experiments. Some important experimental data have been acquired.     

Influence of cesium on the stability of a GaAs photocathode

The stability of a reflection-mode GaAs photocathode has been investigated by monitoring the photocurrent and the spectral response at room temperature.We observe the photocurrent of the cathode decaying with time in the vacuum system under the action of Cs current,and find that the Cs atoms residing in the vacuum system are helpful in prolonging the life of the cathode.We examine the evolution and analyse the influence of the barrier on the spectral response of the cathode.Our results support the double dipolar model for the explanation of the negative electron affinity effect.     

GaAs光电阴极激活时Cs的吸附效率研究

从NEA GaAs光电阴极的激活光电流曲线发现,当系统真空度不很高时,在首次Cs激活阶段,表面掺杂浓度较低的阴极材料,其光电流产生需要的时间也较长.同时,随着系统真空度的提高,这种时间上的差异又变得不再明显.该现象表明,Cs原子在阴极表面的吸附效率同表面层掺杂浓度以及系统真空度之间有直接的联系.为定量分析这种关系,本文根据实验数据建立了Cs在阴极表面吸附效率的数学模型,利用该模型仿真的结果同实验现象非常符合.该研究对进一步开展变掺杂阴极结构设计和制备工艺研究具有重要的价值和意义. 关键词： GaAs光电阴极 吸附效率 真空度 表面掺杂浓度     

Diffusion process of electrons injected from STM tip into AlGaAs/GaAs quantum wells

We have investigated the electron diffusion process in Al_0.3Ga_0.7As/GaAs quantum well (QW) structures by means of scanning tunneling microscope light emission (STM-LE) spectroscopy. The optical measurements were performed on a cleaved (1 1 0) surface at room temperature. The STM-LE spectra were measured by injecting hot electrons from the tip positioned at different distances from the QWs. The emission intensity from individual wells as a function of the tip-well distance was found to decay with two distinct decay constants. From comparison with Monte Carlo simulations for hot electron relaxation, we found that the intervalley scattering from the Γ valley to the L and X valleys has the most significant effect on the diffusion process of the injected electrons.     

直流光阴极注入器电子束壁损失初步研究

真空度被认为是影响GaAs阴极寿命的最重要参数之一,电子束在阴极附近的壁损失会导致真空度下降。基于高斯分布模型,研究了中国工程物理研究院自由电子激光相干强太赫兹源(FEL-THz)直流光阴极注入器电子束在束线管壁上的损失情况。通过理论分析、数值计算、束流动力学模拟、热力学分析及电子束初步出束实验研究,证明了FEL-THz电子束壁损失能达到W量级,必然引起真空度下降和阴极寿命缩短,这是目前限制出束的重要原因之一。研究表明,为维持电子束持续稳定工作,应将注入器阳极后的管道尺寸扩大到至少45mm。     

均匀掺杂GaAs材料光电子的输运性能研究

通过建立原子结构的理论模型和电离杂质散射理论公式,研究了光电子在透射式均匀掺杂GaAs光电阴极体内的输运过程,分析了光电阴极的掺杂浓度、发射层厚度、电子扩散长度等相关因素对阴极出射面的弥散圆斑以及到达阴极出射面的光电子数与激发光电子总数之比的影响.计算结果表明,当透射式均匀掺杂GaAs光电阴极发射层厚度为2 μm、电子扩散长度为3.6 μm、掺杂浓度为1×10¹⁹ cm^-3时,其极限线分辨率为769 mm^-1.此GaAs材料光电子的输运性能 关键词： GaAs 光电阴极 光电子输运 弥散圆斑 分辨率     

直流光阴极注入器电子束壁损失初步研究

真空度被认为是影响GaAs阴极寿命的最重要参数之一,电子束在阴极附近的壁损失会导致真空度下降。基于高斯分布模型,研究了中国工程物理研究院自由电子激光相干强太赫兹源（FEL-THz）直流光阴极注入器电子束在束线管壁上的损失情况。通过理论分析、数值计算、束流动力学模拟、热力学分析及电子束初步出束实验研究,证明了FEL-THz电子束壁损失能达到W量级,必然引起真空度下降和阴极寿命缩短,这是目前限制出束的重要原因之一。研究表明,为维持电子束持续稳定工作,应将注入器阳极后的管道尺寸扩大到至少45 mm。     

Quantum efficiency conversion from the reflection-mode GaAs photocathode to the transmission-mode one

In the article, the transmission-mode negative electron affinity GaAs photocathode is compared with the reflection-mode one in structure, working principle and the quantum efficiency equation. The key point to establish relation between the two modes is that the active-layer is in full accord and the biggest difference is that the incident direction of photons is inverse. Based on the relation and difference above, we obtain the electron escape probability P and the spectrum absorption coefficient α of the reflection-mode GaAs photocathode by multilayer film matrix theory. The quantum efficiency of the transmission-mode GaAs photocathode can be estimated through the coefficients P and α of the reflection-mode one. Two groups of samples are analyzed, the one group contains uniform doping reflection-mode and transmission-mode GaAs photocathodes and the other contains exponential doping ones. Through the analysis and curve fitting, we find that the conversion difference of the uniform-doping is about 11.22% while that of the exponential-doping is about 5.46%. Another four groups of samples with exponential-doping active layer are experimentalized and the differences of them are all less than 6%. The results prove the suggested method is feasible and effective and it is more suitable for the conversion of GaAs photocathode with exponential-doping active layer.