NEA光电阴极的性能参数评估

利用自行研制的动态光谱响应测试系统直接实现NEA光电阴极的光谱响应在线测试,并对光谱响应曲线进行曲线拟合,间接实现了电子表面逸出几率、扩散长度、后界面复合速率及积分灵敏度的评估。对(Cs,O)激活的GaAs反射式光电阴极进行了性能参数评估,给出了测试结果。     

GaAs光电阴极原位光谱响应测试技术研究

阐述了ＧａＡｓ光电阴极的原位光谱响应曲线的测试原理,介绍了ＧａＡｓ光电阴极激活和评估系统,该系统可在ＧａＡｓ光电阴极激活过程中在线测试其在４００～１２００ｎｍ之间的光谱响应曲线,给出并分析了该系统对反射式ＧａＡｓ光电阴极的测试结果。结果表明,利用国产材料激活的ＧａＡｓ光电阴极已为负电子亲和势阴极。     

GaAs光电阴极智能激活研究

研制了一套基于计算机控制的GaAs光电阴极智能激活系统,该系统可在计算机控制下严格按照标准工艺对GaAs光电阴极进行智能激活,并可在线测量阴极的光谱响应曲线.利用该系统分别进行了智能激活和人工激活实验,采集了激活过程中的光电流变化曲线,分析发现,和智能激活过程相比,由于人工激活过程出现了误操作,相邻光电流峰值间的差值下降很快,Cs、O交替的次数也较少.人工激活过程中Cs、O交替6次,光电流最大值为43μA,激活后GaAs光电阴极的积分灵敏度为796μA/lm.智能激活过程中Cs、O交替9次,光电流最大值为65μA,激活后GaAs光电阴极的积分灵敏度为1100μA/lm.     

Cs、O激活方式对GaAs光电阴极的影响

利用自行研制的GaAs光电阴极多信息量测试与评估系统,比较了不同Cs、O激活方式下GaAs光电阴极的激活过程、光谱响应特性以及稳定性的差异,发现与传统的Cs源、O源交替断续激活方式相比,Cs源持续,O源断续的激活方式能获得灵敏度更高和稳定性更好的阴极,且阴极的长波响应能力也得到提高.本文利用双偶极层模型对实验现象进行了解释,认为Cs在整个激活过程中处于轻微过量状态有利于获得高性能的GaAs光电阴极,Cs量控制是决定GaAs光电阴极激活工艺好坏的主要因素.     

GaAs光电阴极制备过程中多信息量测试技术研究

研制了一套基于现场总线技术的GaAs光电阴极多信息量测试系统，该系统可在线测试和保存阴极制备过程中的大部分信息量，如激活系统的真空度、阴极光电流、光谱响应曲线、Cs源和O源电流等。实验测试了GaAs光电阴极加热净化过程中真空度随温度的变化曲线，分析发现，高温净化时有几个真空度下降较快的区域，为160℃～280℃、400℃～500℃、570℃～600℃，分别是由于．AsO的脱附和水分的蒸发、As2O3分解和Ga2O脱附、GaAs和Ga2O3的分解所致，低温净化真空度在370℃后下降较快，这是由于吸附在阴极表面的Cs脱附速度加快造成的。实验还测试了激活过程中多种信息量的变化，发现了真空度和光电流随Cs源和O源电流的变化规律，这些大大方便了对激活工艺进行深入细致的分析研究。     

多碱光电阴极多信息量测试技术研究

阐述了多碱光电阴极的单色光反射比、单色光电流和光谱响应曲线的测试原理 ,这些参量的获得对分析、指导阴极工艺是很有价值的。介绍了多碱光电阴极多信息量测试系统 ,该系统可在多碱光电阴极制备过程中在线测试、处理多碱阴极的单色光反射比、单色光电流和光谱响应曲线等参量 ,还给出并分析了在该系统应用于玻璃阴极实验管制备过程中的测试结果     

多碱光电阴极多信息量测试技术研究

阐述了多碱光电阴极的单色光反射比、单色光电流和光谱响应曲线的测试原理,这些参量的获得对分析、指导阴极工艺是很有价值的。介绍了多碱光电阴极多信息量测试系统,该系统可在多碱光电阴极制备过程中在线测试、处理多碱阴极的单色光反射比、单色光电流和光谱响应曲线等参量,还给出并分析了在该系统应用中玻璃阴极实验管制备过程中的测试结果。     

三代微光管均匀性测试与分析

利用自行研制的“光电阴极多信息量测试系统”首次对国产三代微光管中的GaAs光电阴极的均匀性进行了光谱响应测试 ,结果表明该国产三代微光管存在明显的非均匀性。利用曲线拟合方法估算了GaAs光电阴极的材料性能参数 ,发现表面逸出概率不一致是非均匀性的主要原因 ,GaAs材料的少子扩散长度 (1 1 2～ 1 82 ) μm ,与阴极厚度相当 ,后界面复合速率在 (1× 1 0 5～ 1× 1 0 6 )cm/s之间 ,它限制了阴极灵敏度的提高     

负电子亲和势光电阴极评估技术研究

阐述了负电子亲和势(NEA)光电阴极的评估原理,用NEA光电阴极的量子产额理论曲线对测试获得的实验曲线进行拟合,可以获得光电阴极的表面逸出概率、载流子扩散长度和后界面复合速率等参数.介绍了NEA光电阴极激活和评估系统,利用该系统对国产的反射式GaAs基片进行了激活和评估,文中给出并分析了测试结果.     

负电子亲和势光电阴极评估技术研究

阐述了负电子亲和势（NEA）光电阴极的评估原理,用NEA光电阴极的量子产额理论曲线对测试获得的实验曲线进行拟合,可以获得光电阴极的表面逸出概率、载流子扩散长度和后界面复合速率等参数。介绍了NEA光电阴极激活和评估系统,利用该系统对国产的反射式GaAs基片进行了激活和评估,文中给出并分析了测试结果。     

Comparative research on GaAs photocathodes before and after activation

Obtaining higher quantum efficiency and more stability has been an important developing direction in the investigation of GaAs photocathodes. By solving the one-dimensional diffusion equation for no-equilibrium minority carriers of reflection-mode GaAs photocathode materials, we can get the equations of the surface photovoltage curve before activation and the spectral response curve after activation for uniform and exponential doping GaAs materials. Through experiments and fitting calculations for two doping structural materials designed by us, the parameters of the body materials are exactly measured by the surface photovoltage curves, and the curves for surface escape probability are also accurately fitted by the comparative research before and after activation. The differences for the fitting results of two doping structures are also well analyzed. This comparative research can form a closed-loop research for GaAs photocathodes and will help us to deeply study the varied doping structures and optimize Cs-O activation technology for GaAs photocathodes in the future.     

Spectral response variation of a negative-electron-affinity photocathode in the preparation process

In order to research the spectral response variation of a negative electron affinity (NEA) photocathode in the preparation process, we have done two experiments on a transmission-type GaAs photocathode. First, an automatic spectral response recording system is described, which is used to take spectral response curves during the activation procedure of the photocathode. By this system, the spectral response curves of a GaAs:Cs-O photocathode measured in situ are presented. Then, after the cathode is sealed with a microchannel plate and a fluorescence screen into the image tube, we measure the spectral response of the tube by another measurement instrument. By way of comparing and analyzing these curves, we can find the typical variation in spectral-responses. The reasons for the variation are discussed. Based on these curves, spectral matching factors of a GaAs cathode for green vegetation and rough concrete are calculated. The visual ranges of night-vision goggles under specific circumstances are estimated. The results show that the spectral response of the NEA photocathode degraded in the sealing process, especially at long wavelengths. The variation has also influenced the whole performance of the intensifier tube.     

变掺杂GaAs光电阴极的研究进展

从变掺杂阴极的结构种类、变掺杂GaAs光电阴极的光电发射机理、制备技术以及变掺杂结构对阴极性能的影响等方面介绍了当前国内研究变掺杂GaAs光电阴极的进展.目前该工作还处于起步阶段,理论研究还有待于进一步深入.开展变掺杂阴极研究是我国走自主创新道路、提高国内三代微光器件性能的有效途径.     

光阴极材料GaAs/AlGaAs的组分分析

为探索砷化镓光阴极的光电灵敏度的影响因素 ,利用X射线光电子能谱、二次离子质谱和电化学方法测试和分析了国内和国外GaAs光阴极材料GaAs/AlGaAs的C ,O含量和空穴浓度分布。实验发现 ,国内的材料在GaAs/AlGaAs界面及AlGaAs层的O含量分别为 7 6 %和 10 6 % ,C浓度分别为 5 2×10 18atoms/cm3和 1 0× 10 19atoms/cm3,而国外的材料的O含量相应为 1 0 %和 1 5%。国内的材料GaAs和AlGaAs层的空穴浓度分别为 7× 10 18～ 4× 10 19cm- 3和 8× 10 17cm- 3,而国外材料的相应值分别为 (1 8～ 2 0 )× 10 19cm- 3和 5× 10 18cm- 3。分析认为 ,层中及界面的C ,O杂质偏高和空穴浓度分布不尽合理使光电子扩散长度减小 ,后界面复合增大 ,导致了光电灵敏度下降。     

Effect of different epitaxial structures on GaAs photoemission

The quantum efficiency equations of two different structure reflection-mode GaAs photocathodes with back interface recombination velocity have been solved from the diffusion equations. One structure consists of GaAs substrate and an epitaxial GaAs active layer (GaAs-GaAs) and another structure consists of GaAs substrate, an epitaxial AlGaAs buffer layer, and a GaAs active layer (AlGaAs-GaAs). The experimental results show that the quantum efficiency of long-wavelength photons and the integral sensitivities for GaAs-GaAs cathodes both increase with the increase in the active layer thickness, which is due to the increase of electron diffusion length. The quantum efficiency of long-wavelength photons and the integral sensitivity of AlGaAs-GaAs cathodes are greater than those of GaAs-GaAs cathodes with an identical active layer thickness, which is attributed to the AlGaAs buffer layer. The buffer layer can reflect electrons and improve the quality of the GaAs active layer. Through the theoretical simulation, we found the active layer thickness for AlGaAs-GaAs cathodes has an optimum value at which the cathodes achieve the maximum sensitivity.     

Suppression of afterpulsing in photomultipliers by gating the photocathode

A number of gating schemes to minimize the long-term afterpulse signal in photomultipliers have been evaluated. Blocking the excitation pulse by gating the photocathode was found to reduce the gate-on afterpulse background by a factor of 230 over that for nongated operation. This afterpulse or signal-induced background (SIB), which is particularly troublesome in stratospheric lidar measurements, appears as a weak exponentially decaying signal extending into the millisecond region after the photomultiplier tube (PMT) is exposed to an intense submicrosecond optical pulse. Photocathode gating is not feasible in PMTs with semitransparent bialkali photocathodes because of their slow gate response time, but is easily implemented in PMTs with opaque bialkali or semitransparent multialkali (S-20) photocathodes that can be gated with nanosecond response. In those PMTs with semitransparent bialkali photocathodes, a gated (adjacent) focus grid (if available) also produces a significant reduction in the SIB.     

多碱光电阴极光谱响应在线测试结果与分析

介绍了多碱光电阴极制备过程中测试的光谱响应，并作了简单分析。研究结果表明，Sb，K交替决定双碱化合物Na_2KSb的导电类型，Cs处理降低Na_2KSb的电子亲和势，延伸长波阈；Sb，Cs交替形成锑铯偶极层，在Na_2KSb上吸附的铯原子数和感应的偶极层的偶极矩同时影响多碱光电阴极的灵敏度。     

Comparison of structure and performance between extended blue and standard transmission-mode GaAs photocathode modules

Extended blue and standard transmission-mode GaAs photocathode modules were prepared, respectively, by metal organic chemical vapor deposition. The experimental reflectivity, transmissivity, and spectral response curves were measured and compared separately. The integral sensitivities are 1980 μA/lm and 2022 μA/lm for both the modules. By use of the revised quantum yield formula, the experimental spectral response curves are fitted to obtain the structure parameters. The fitted results show that the Ga(1-x)Al(x)As window layer with varied aluminum components is beneficial to improve extended blue GaAs photocathode module. In addition, the layer-thickness and aluminum component in the window layer determine the extended blue performance, while the thickness of the GaAs active layer settles the long-waveband performance for the transmission-mode GaAs photocathode module.     

NEA GaAs光电阴极表面和UHV系统微颗粒污染的寻源分析与排除

借助于扫描电镜和能量分散X-ray能谱分析方法,对发生在超高真空(UHV)系统内,负电子亲和势GaAs光阴极表面上的金属微颗粒污染物进行了分析研究。给出了存在于表面上微颗粒污染物的性质、类型、所占比例、构成成分、形貌、几何尺寸。介绍了寻找、排除微颗粒污染物的方法,并由成分分析结果,找到并排除了UHV系统内Mo微颗粒污染物产生的源头。发现在UHV系统内,传递杆等可移动部件的较粗糙表面具有携带、输运、抛撒微颗染污染物的功能。对UHV系统进行了全面的清洗处理,使其恢复到了原有的正常状态。