Na_2KSb光电阴极与GaAs光电阴极比较研究

测量了三代像增强器和超二代像增强器的阴极光谱反射率,结果表明在500～800 nm波长范围内,GaAs阴极的平均光谱反射率仅为6.5%,而Na2KSb阴极的平均光谱反射率却高达22%。采用减反技术之后,Na2KSb阴极的平均光谱反射率降为10%,与GaAs阴极相比还有一定的差距,因此还有进一步改进和提高的空间。测量了三代像增强器和超二代像增强器光电阴极的荧光谱,结果表明在785 nm波长激光的激发条件下,GaAs阴极的荧光谱峰值波长与Na2KSb阴极的荧光谱峰值波长基本相同,但荧光谱半峰宽和峰值强度却区别很大。说明GaAs阴极和Na2KSb阴极在吸收785nm波长光子后,所激发的电子跃迁的能级基本相同,但跃迁电子的数量区别却很大。GaAs阴极荧光谱的半峰宽较窄,说明GaAs阴极的晶格较Na2KSb阴极的晶格更完整。当Na2KSb阴极的膜层厚度从180 nm变为195 nm之后,由于跃迁电子距真空界面的距离增大,因此导致短波的量子效率减小。尽管膜层厚度加厚,长波光子的吸收更充分,但因受到电子扩散长度的限制,长波量子效率仅仅略有增加。这说明Na2KSb阴极的电子扩散长度远远小于GaAs阴极的电子扩散长度。GaAs阴极表面吸附Cs-O层之后,表面电子亲和势会降低,而多碱阴极表面吸附Cs-Sb层之后,不仅表面电子亲和势会降低,而且跃迁电子的能级会提高,跃迁电子的数量也会增加,这说明多碱阴极在进行表面Cs激活之后,阴极膜层内部的能带结构发生了变化。所以要提高多碱阴极的灵敏度,除了要控制好表面的Cs激活工艺之外,还需要控制好Na2KSb基础层的结构。只有一个结构良好的Na2KSb基础层,在Cs激活之后,能带结构的变化才会有利于跃迁电子能级的提高。     

多碱阴极激活过程中逸出功及电子跃迁变化研究

测量了未经过Cs激活、经过Cs激活以及经过Cs-Sb激活的三种多碱阴极的光谱响应及荧光谱。测量结果表明,Na2KSb阴极膜层经表面激活之后,阴极灵敏度和长波截止波长均有所增加,但荧光谱的峰值波长和峰值荧光强度基本保持不变。长波截止波长的增加说明逸出功降低,因此多碱阴极Na2KSb膜层经Cs激活之后,阴极灵敏度提高和长波截止波长增加的原因是逸出功的降低。Na2KSb膜层同时经过Cs-Sb激活之后,阴极灵敏度和长波截止波长较仅仅经过Cs激活的多碱阴极有进一步更大幅度的提高和增加,但同时荧光谱的峰值波长向短波方向移动,峰值荧光强度增加。荧光谱的峰值波长向短波方向移动,说明跃迁电子的能级有所升高,而荧光谱的峰值强度增加,意味着跃迁电子的数量增加。多碱阴极Na2KSb膜层经过Cs-Sb激活之后,跃迁电子的数量增加以及跃迁电子的能级升高,对阴极灵敏度的提高而言,所取得的作用相同。因此多碱阴极Na2KSb膜层经过Cs-Sb激活之后,阴极灵敏度和长波截止波长提高的原因除了表面逸出功降低之外,还有跃迁电子数量增加以及跃迁电子能级提高的原因。多碱阴极表面电子逸出机理至今仍未定论,因此要进一步提高多碱阴极的灵敏度,需要进一步研究多碱阴极表面激活过程中的客观规律,为进一步改进多碱阴极的制作工艺,提高多碱阴极的灵敏度提供理论指导。     

第三代象增强器

引言三代象增强器是一种采用GaAs光电阴极的双近贴象管。二代管和三代管的主要差别在于光电阴极。1965年负电子亲和势光电阴极的发现是新型光电发射作研究的起点。1975年Antypas和Edgecumbe实现了GaAs/GaAlAs双异质结结构,为制作高质量GaAs透射式光电阴极提供了可能性。从那时起,人们就着手研究三代象增强器。在GaAs光电阴     

超二代像增强器多碱阴极电子逸出机理研究

测量了超二代像增强器多碱阴极的光谱反射率和透射率,计算了多碱阴极的光谱吸收率。从光谱吸收率看出,当波长大于850 nm以后,多碱阴极的吸收率下降很快,但当波长大于915 nm之后,吸收率的下降变慢,同时吸收率低于5%。这说明多碱阴极的Na2KSb膜层存在一个915 nm的长波吸收限,入射光的波长如果大于该吸收限,多碱阴极将不吸收。多碱阴极在吸收光子之后的电子跃迁过程中,跃迁电子的能量增加小于所吸收的光子能量,即存在"能量损失"。光子的能量越高,跃迁电子的能级越高,能量损失越大。超二代像增强器Na2KSb阴极膜层在Cs激活之后,荧光的峰值波长向短波方向移动,发生"蓝移"现象,表明多碱阴极Na2KSb膜层在进行表面Cs激活之后,跃迁电子的能级有所升高。多碱阴极无论是单独采用Cs激活还是采用Cs、Sb同时激活,光谱响应的长波阈值基本相同,但光谱响应却不相同,原因是采用Cs、Sb同时激活时,Na2KSb阴极膜层存在"体积"效应。由于Na2KSb阴极存在长波吸收限,对应的光子能量为1.35 eV,因此如果多碱阴极的逸出功进一步降低并且低于1.35 eV时,尽管多碱阴极的光谱响应会进一步提高,但光谱响应的长波阈并不会向长波方向延伸,此时多碱阴极光谱响应的长波阈值由其长波吸收限所决定。     

欧洲超二代像增强器技术的选择及进一步发展

二代像增强器采用Na₂KSb光电阴极,三代像增强器却采用GaAs光电阴极。由于GaAs光电阴极具有更高的阴极灵敏度,因此三代像增强器的性能远高于二代像增强器。在二代像增强器基础上发展的超二代像增强器,阴极灵敏度有了很大提高,因此性能也有很大提高,同时大大缩短了与三代像增强器的性能差距。超二代像增强器属于Na₂KSb材料体系,生产成本低,与三代像增强器相比性价比较高,所以欧洲的像增强器产商选择了超二代像增强器技术的发展路线。超二代与三代像增强器技术并行发展了30多年,两者性能均有大幅提高。超二代与三代像增强器的性能差距主要体现在极低照度（＜10－4 lx）条件下,而在其它照度条件下,性能基本相当。超二代像增强器的性能仍有提高的空间。增益方面,在微通道板的通道内壁上制作高二次电子发射系数的材料膜层可以提高增益;信噪比方面,采用光栅窗可提高阴极灵敏度,从而提高信噪比;分辨力方面,在微通道板输出端制作半导体膜层、采用高清荧光屏均可提高分辨力。阴极灵敏度是光电阴极的指标,不是像增强器的整体性能指标。阴极灵敏度对像增强器整体性能的影响体现在增益、信噪比以及等效背景照度指标中。无论是超二代还是三代像增强器,都区分不同的型号。不同型号的超二代或三代像增强器性能均不相同。超二代和三代像增强器的性能指标是在A光源条件下测量的,而A光源光谱分布与实际应用环境中的光谱分布并不等同,同时Na₂KSb和GaAs光电阴极的光谱分布不相同,所以超二代和三代像增强器的信噪比、分辨力等性能指标不具备可比性。     

K2Te日盲紫外阴极研究

叙述了K2Te日盲紫外阴极的制作工艺并制作了K2Te日盲紫外阴极,测量了K2Te日盲紫外阴极的光谱响应、光谱反射率、光谱吸收率和250 nm波长激发条件下的荧光谱。与Cs2Te日盲紫外阴极相比较,K2Te日盲紫外阴极的光谱响应较低,而且光谱响应的峰值波长更短,长波截止波长也更短。K2Te日盲紫外阴极光谱响应的峰值波长位于215 nm,长波截止波长位于305 nm,而Cs2Te日盲紫外阴极光谱响应的峰值波长位于250 nm,长波截止波长位于323 nm。另外K2Te日盲紫外阴极的日盲特性更好,633 nm波长的光谱响应为10－6 mA/W的数量级,较Cs2Te日盲紫外阴极低一个数量级。光谱反射率的测量结果表明,K2Te日盲紫外阴极的光谱反射率曲线形状与Cs2Te日盲紫外阴极的光谱反射率曲线形状相似,区别是整个光谱反射率曲线向短波方向移动,且波长越长,移动越大。另外K2Te日盲紫外阴极的光谱反射率在200～450 nm的波长范围内均高于Cs2Te日盲紫外阴极的光谱反射率,由此可推断出K2Te 紫外阴极的折射率高于Cs2Te 紫外阴极的折射率,并且波长越长,折射率差别越大。光谱吸收率的测量结果表明,K2Te 日盲紫外阴极的吸收率低于Cs2Te 紫外阴极的吸收率。光谱吸收率越高,光谱响应也越高,与光谱响应的测量结果相吻合。荧光谱的测试结果表明,在250 nm 波长激发条件下,在200～450 nm 的波长范围内,K2Te 紫外阴极的荧光弱于Cs2Te 紫外阴极的荧光,原因是K2Te 阴极的吸收率低于Cs2Te 紫外阴极的吸收率。光谱吸收率越高,荧光越强,这同样与光谱响应的测试结果相吻合。所以K2Te 日盲紫外阴极与Cs2Te 日盲紫外阴极相比,尽管光谱响应较低,但日盲特性更好,因此也可用作为日盲紫外探测器的紫外阴极。     

超二代与三代像增强器性能的比较研究

超二代和三代像增强器是两种不同技术的像增强器,其在光电阴极、减反膜、离子阻挡膜以及阴极电压方面存在区别。在极限分辨力方面,尽管三代像增强器GaAs光电阴极的电子初速小、出射角分布较窄以及阴极电压较高,但目前两种像增强器的极限分辨力均相同,三代像增强器GaAs光电阴极的优势在现有极限分辨力水平下并未得到发挥。在信噪比方面,尽管GaAs光电阴极具有更高的阴极灵敏度,但因为较高的阴极电压以及离子阻挡膜透过率的影响,使得两种像增强器的信噪比基本相同,三代像增强器GaAs光电阴极高灵敏度的优势也未得到发挥。在增益方面,尽管三代像增强器具有更高的阴极灵敏度以及较高的阴极电压,但超二代像增强器通过提高微通道板的工作电压来弥补阴极灵敏度以及阴极电压的不足,因此在现有像增强器增益的条件下,两种像增强器的增益完全相同。在等效背景照度方面,由于三代像增强器GaAs光电阴极的灵敏度更高,因此在相同光电阴极暗电流的条件下,三代像增强器可以获得更低的等效背景照度,所以三代像增强器较超二代像增强器具有更高的初始对比度。在光晕方面,由于三代像增强器光电阴极的灵敏度较高,同时具有离子阻挡膜,因此理论上讲,三代像增强器较超二代像增强器具有更高的光晕亮度,但实际的情况是两种像增强器的光晕亮度基本相同。在杂光方面,GaAs光电阴极具有减反膜,因此杂光较超二代像增强器低,所以三代像增强器的成像更清晰,层次感更好。在带外光谱响应方面,由于超二代像增强器Na₂KSb（Cs）光电阴极的带外光谱响应高于三代像增强器,因此在近红外波段进行辅助照明时,超二代像增强器较三代像增强器成像性能更好。在低照度分辨力方面,具有相同性能参数的超二代和三代像增强器具有相同的低照度分辨力。需要注意的是,这是在标准A光源测试条件下所得出的结论。当实际的环境发射光谱分布与标准A光源发射光谱分布不相同时,两种像增强器的低照度分辨力将会不同。     

不同结构的反射式GaAs光电阴极的光谱特性比较

利用分子束外延生长了三种结构的反射式GaAs光电阴极,其中一种为传统结构的反射式GaAs光电阴极,另外两种为具有GaAlAs缓冲层的均匀掺杂和梯度掺杂反射式GaAs光电阴极.激活后的光谱响应测试结果表明,与传统结构的反射式GaAs光电阴极相比,具有GaAlAs缓冲层的均匀掺杂反射式GaAs光电阴极的长波响应更好,而具有...     

阴极光电发射受电场影响的研究

本文叙述了电场对光电发射的影响.许多阴极在外电场的作用下会降低表面功函数,光电发射的阈值波长会延伸,长波响应也会增大.高阻值碱金属化合物阴极在光电发射过程中由于内电场的形成,有可能对发射层进行"侵蚀"从而导致损坏.     

基于异变缓冲层与应变层超晶格的InP/GaAs异质外延

利用低压金属有机化学气相沉积技术, 开展InP/GaAs异质外延实验。由450 ℃生长的低温GaAs层与超薄低温InP层组成双异变缓冲层, 并进一步在正常InP外延层中插入In1-xGaxP/InP(x=7.4%)应变层超晶格。在不同低温GaAs缓冲层厚度、应变层超晶格插入位置及应变层超晶格周期数等条件下, 详细比较了InP外延层(004)晶面的X射线衍射谱, 还尝试插入双应变层超晶格。实验中, 1.2 μm和2.5 μm厚InP外延层的ω扫描曲线半峰全宽仅370 arcsec和219 arcsec; 在2.5 μm厚InP层上生长了10周期In0.53Ga0.47As/InP 多量子阱, 室温PL谱峰值波长位于1625 nm, 半峰全宽为60 meV。实验结果表明, 该异质外延方案有可能成为实现InP-GaAs单片光电子集成的一种有效途径。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.