MBE梯度掺杂GaAs光电阴极激活实验研究

本文首次利用分子束外延(MBE)生长了多种由体内到表面掺杂浓度由高到低的梯度掺杂反射式GaAs光电阴极材料,并进行了激活实验,结果表明,表面低掺杂浓度适中,外延层厚度2 μm～3 μm以及衬底为重掺杂p型GaAs的梯度掺杂GaAs光电阴极能够获得较高灵敏度.在优化激活工艺的条件下,梯度掺杂GaAs光电阴极获得了1798μA/lm的最高积分灵敏度,比采用同样方法制备的均匀掺杂GaAs光电阴极高30%以上.梯度掺杂GaAs光电阴极表面掺杂浓度较均匀掺杂的低,第一次给Cs时间较长,第一次Cs、O交替时要调整好Cs/O比,并在整个激活过程中保持不变.一个高量子效率梯度掺杂GaAs光电阴极的获得依赖于梯度掺杂结构和激活工艺两个方面的优化.     

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.     

透射式GaN光电阴极在正面光照和背面光照下的量子效率特性研究

研究了透射式GaN光电阴极在正面光照和背面光照两种工作模式下的光电发射特性差异及影响因素,并推导了这两种工作模式下的量子效率理论公式,利用所推导的公式对实验获得的GaN光电阴极量子效率曲线进行了分析。研究结果表明,两种工作模式下光电子的表面逸出几率与光子能量具有不同的依赖关系,背面光照下,光电子将以一个一致的表面逸出几率从表面发射出去,并且短波响应会受到缓冲层及界面特性的影响,总体光电发射效率依赖于阴极表面势垒所决定的平均电子逸出几率。利用所推导的量子效率公式对实验曲线进行拟合,可实现多个阴极参量的评估,这为透射式GaN阴极材料与制备工艺水平的分析提供了重要依据。     

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。     

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。     

三碱光电阴极S_(20)与LEP主要差别的研究

本文用多碱阴极量子产额谱研究了S_(20)与LEP的主要差别。阐述了如下几个问题:1.阴极厚度D是造成两者差别的主要原因。在n、k不随阴极厚度变化的情况下,适当增加D可以得到性能优越的光电阴极。2.较厚的阴极具有较大的有效吸收系数α_p(hv),有利于增加长波光电发射。3.逸出几率与光电子产生位置有关,一般距真空界面越近,逸出几率越大。     

负电子亲和势GaN 阴极光电发射机理研究

GaN阴极中光电子的发射分为价带电子的激发、光生载流子的输运和载流子的发射3个阶段。分析了激发阶段GaN光电阴极中电子吸收入射光产生从价带到导带的跃迁过程和输运阶段导带中的光电子从体内到表面的扩散过程及发射阶段GaN阴极表面光电子的逸出过程;推导了Cs激活过程中到达阴极表面光激发电子的逸出几率公式;比较了仅用Cs激活和共用Cs/O激活过程中到达阴极表面光激发电子逸出几率的变化情况;结果表明:GaN阴极的光电发射为直接跃迁激发,输运阶段仅遭受电子-声子散射,表面光激发电子的逸出几率取决于激活程度,引入Cs是激活的必需因素,O的引入仅可小幅度提升光电发射效率;最后利用实验证实了Cs激活的充分性。     

n-InP/p-InP/p-InGaAs场助光电阴极理论建模与仿真

场助光电阴极与通常的负电子亲和势光阴极相比,能显著延长长波阈值,因此在近红外光探测中有着广阔的应用前景。本文利用二维连续性方程建立了n-InP/p-InP/p-InGaAs场助光阴极的电子发射模型。通过模型模拟得到了电子发射电流,并计算了外量子效率。分析了不同偏压下外延层的掺杂浓度和厚度对量子效率的影响,根据仿真结果及制备条件限制,确定了阴极外延结构的最佳参数:n-InP接触层的掺杂浓度为1×10¹⁹/cm³,厚度为0.2μm;p-InP发射层的掺杂浓度为2.2×10¹⁸/cm³,厚度为25 nm;p-InGaAs吸收层的掺杂浓度为5×10¹⁷/cm,,厚度为3μm。对电极和发射面的宽度进行了模拟,发射单元表面的宽度最佳范围为5～8μm,并分析了不同偏压下电极宽度和发射面宽度对量子效率的影响。为场助光电阴极的结构设计和应用提供了理论基础,有利于场助光电阴极的制备。n-InP/p-InP/p-InGaAs场助光电阴极有效提高了发射电流效率,室温5 V偏压下外量子效率在1.55μm...     

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     

高温贮存对GaAs光电阴极光电发射性能影响研究

为了研究高温贮存对GaAs光电阴极光电发射性能的影响,以2只GaAs光电阴极像增强器为研究对象,参照美军标MIL-STD-810F规定,对它们分别进行了70℃、48 h高温贮存实验。在实验过程中间隔一定时间测量一次其光电阴极灵敏度,随后利用Matllab软件和量子效率公式,计算了GaAs光电阴极参数,拟合了量子效率曲线。结果表明,GaAs光电阴极在70℃经过3~4 h贮存后,GaAs体材料与Cs-0表面层材料形成的光电发射层将达到稳定结构。研究成果为高性能GaAs光电阴极像增强器研制提供了技术支撑。     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to     

Win-Win Cooperation

正The Chinese Premier Li Keqiang's recent trip to the UK has reinforced the China-UK comprehensive strategic partnership;just as the British Prime Minister David Cameron put it,"the relationship is gaining in strength,depth and understanding"after a bucket of business deals being inked worth more than 30 billion US dollars.From the first agreement signing in 2004 to the new agreement of mutual standards recognition and adoption in     

Systematic Approach for Emerging Industry

正A national directory of standards complexes for strategic emerging sectors was recently developed and released jointly by 12governmental departments,namely,SAC,NDRC,MOST,MIIT,MEP,MOA,AQSIQ,State Forest Administration,State Administration of Science and Technology for National Defense,State Oceanic Administration and National Railway Administration.     

Strictest Pollutants Emission Standards

正Four new national standards on air pollutant emission control offi cially issued by the Ministry of Environment Protection(MEP)together with AQSIQ and SAC has been brought into force from July 1,2014.The Emission standard for air pollutants of coal-burning,oil-burning and gasfi red boilers,which is the strictest emission standard historically,will tackle the stubborn pollution problem of boilers and waste incineration in most of China’s regions.     

Instructions to Authors

New Carbon Materials is a bimonthly journal published with the permission of the Ministry of Science and Technology and of the State News and Publication Agency.The journal is sponsored by the Institute of Coal Chemistry,Chinese Academy of Sciences,and is published by Science Press.Aims and Scope     

Progress on Standards Copyright Protection

正Recently,National Copyright Administration of China(NCAC)has rewarded 215 organizations and 179 individuals for their outstanding efforts on investigating standards copyright infringement and piracy in 2013.Hua Jianhua,the Deputy-Director of National Standards Copyright Protection Workgroup Office won a third prize of the national individual award.In 2012,SAC set up the national standards copyright protection working group,and developed policies to crack down standards infringement and piracy behaviors and to strengthen standards copyright protection.