双门聚焦结构场发射阵列阴极的计算机模拟

采用有限差分算法,对双门聚焦结构的场致发射阵列阴极进行了三维模拟计算,得到了锥尖处的电场强度,电子的运动轨迹及电位分布图.结果表明,聚焦极电位、聚焦极孔半径及聚焦极与栅极间距的变化对锥尖电场影响不大,但对电子轨迹影响很大.当聚焦极电位超过140 V时,电子束的会聚作用消失;低于-30 V时,电子束轨迹出现交叉.减小聚焦极孔径可以加强电子束的会聚作用,但当其减小至0.75 μm时,聚焦极会捕获部分边缘电子.因此在实际确立聚焦极参量时,应主要从聚焦极对电子束轨迹的会聚作用方面考虑,其次再考虑聚焦极对锥尖场强的影响.     

碳纳米管冷阴极电子枪的电子光学设计

基于皮尔斯电子枪设计理论,提出了一种碳纳米管场致发射阴极电子枪的电子光学设计方案。电子枪阴极半径为0.5 mm,保持阴阳极电压不变,动态调整栅极电压,并利用计算机技术仿真软件（CST）对其进行仿真优化研究;结果表明,栅极最佳电压值为-14 kV,对应阴极发射电流为15.08 mA,阳极处电子束半径约为0.1 mm。研究为碳纳米管冷阴极栅极结构的设计提供了一种新的思路。     

应用于LCD的平栅型碳纳米管场致发射显示器背光源的研制

采用磁控溅射、光刻和湿法刻蚀技术制备平栅型场发射阴极阵列,利用电泳将碳纳米管(CNT)发射源沉积在阴极表面,将阴极板和阳极板封接后制成51cm单色平栅型CNT场致发射显示器(CNT-FED),作为背光源模板应用于49 cm液晶显示器(LCD)器件中.场发射测试表明,器件在阳极电压3 500V、栅极电压290 V时,阳极...     

材料表面形貌对激光冲击强化残余应力的影响

建立材料表面为凹面、凸面和平面的三种有限元模型,研究材料表面形貌对激光冲击强化Ti6Al4V钛合金残余应力的影响。当材料表面曲率半径大于光斑半径时,相对于材料表面为平面的工况,凹面表层产生的残余压应力偏大,并随着凹面曲率半径的减小而增大;凸面表层产生的残余压应力偏小,并随着凸面曲率半径的减小而减小。当材料表面曲率半径小于光斑半径时,凹面或凸面模型的激光冲击强化的残余压应力均不及于材料表面为平面的工况。     

具有汇聚特性的场发射电子源的模拟研究

提出了一种具有汇聚特性的新型场发射阴极结构,利用有限元方法模拟计算了此种阴极结构在不同参数条件下的电场分布、电子轨迹,考察了不同参数对电子汇聚效果的影响,给出了此种场发射阴极的栅极-阴极间距、栅极宽度、阳极电压、栅极电压等基本参数对汇聚效果的影响.模拟计算结果表明,电子束的汇聚程度随着栅极-阴极间距的增大而增大,随着栅极宽度的增大而减小;电子束的汇聚程度与阳极电压、栅极电压参数密切相关,并存在最优参数.     

冷阴极X射线管关键部件的设计与仿真

利用CST粒子工作室软件设计仿真了一种高电子通过率冷阴极微焦点X射线管。重点分析X射线管阴极结构、栅网和聚焦极的结构与电压、阳极电压等关键因素对电子束聚焦束斑的影响,特别是设计了一种独特的阴极凹槽结构,使阴极电子束发射的散角减小了21.84°,并使电子枪通过率从54.3%增加至74.59%。在此基础上设计的碳纳米管X射线管在阳极电压为70 kV时,电子通过率可达到75%,电子束焦点约为56 μm,聚束比为5∶1,可为冷阴极微焦点X射线管的设计和加工提供参考。     

微小孔径场发射阵列的电子束特性数值模拟

以场发射基本原理为基础,简化三极管阵列模型,采用有限差分法对微孔径场发射阵列进行了三维模拟.通过改变栅极孔径和尖锥高度并保持其它参数不变的情况,从而获得阳极电子束斑的直径.得到不同情况下的阳极电子束光斑直径的变化.分析了导致电子束光斑大小变化的原因.得出与实际相符合的数值模拟,为试验提供设计依据.     

基于电流源控制的CNT-FED驱动电路设计

本文为了实现碳纳米管场致发射显示器（CNT-FED）的产品化,采用CNT-FED阴极电流源驱动方法,研究了CNT-FED亮度的均匀性和非线性调节问题。从分立元件驱动电路设计原理出发,采用了高稳定性阴极电流源像素驱动电路,将电流源驱动电路预先制作在硅基底上,再利用室温下生长碳纳米管（CNT）的方法,将CNT发射体和电流源驱动电路集成在同一硅衬底上,最终实现了集成CNT-FED驱动电路的设计。该驱动电路解决了CNT-FED亮度均匀性和非线性调节问题,对场射显示器驱动电路的应用研究和CNT-FED驱动电路的集成化具有参考意义。本文网络版地址：http：//www.eepw.com.cn/article/276357.htm     

0800半导体微电子技术与纳米技术

0519179新型 CNT-FED 栅极结构表面二次电子发射研究[刊.中]/王琦龙//应用科学学报.—2005,23(3).—265-268(C2)0519180大尺寸 CNT-FED 阴极制备研究[刊,中]/王琦龙//应用科学学报.—2005,23(3).—261.264(C2)提出了两种碳纳米管场致发射阴极的制备方法,包括雾化喷涂法和丝网印刷法.对碳纳米管的提纯分散、浆料配制、浆料喷涂和印刷方法等进行了细致的研究,并结合模型计算、电镜分析、发射性能测试,对两种制备发射阴极的方法进行了比较和分析,结果表明丝网印刷阴极技术更适用于大尺寸的碳纳米管场致发射显示。文中对阴极后处理技术也进行了相关的讨论。参5     

基于等离子体电子枪的束-等离子体系统研究

采用PIC模拟研究了基于等离子体电子枪的小型化束-等离子体系统,探索了等离子体电子枪发射电流随加速电压、阴极等离子体密度、电子束通道半径以及电子束通道长度的变化规律,展示了电子束在高密度等离子体中的聚焦传输行为.     

Optimization of electron beam focusing for gated carbon nanotube field emitter arrays

We fabricated gated field emitter arrays with a novel focusing structure of electron beams, where the focusing electrode concentrically surrounded each gate hole. Carbon nanotube emitters were screen printed inside an amorphous-Si concave well far below the gate. It was theoretically and experimentally verified that the concave well structure effectively focused the emitted electron beams to their designated phosphor pixels by modulating focusing gate voltages. For the vacuum packaged field emission displays with the pixel specification fitting high-definition televisions, color reproducibility of approximately 71% was achieved at the brightness of 400 cd/m/sup 2/.     

On relationship between the field at an autoemitter top, anode voltage and cathode geometry

Currently a lot of electron emission experiments both in carbon nanotubes with top curvature radius <1 nm, and in emitters as short as 10³ nm with top curvature radius of some tens nanometer are carried out. Experimental results can be explained by a tunnel emission through potential barrier in vacuum near the solid-state cathode border making use of Fowler-Nordheim law. However, in case of cathodes with radius of top curvature less than 100 nm this law is not valid.To proof this statement, the potential of an autoemission diode consisting of a tip cathode located on a flat metal base and flat anode, its dependence on the shape, height of the tip as well as voltage drop on it were calculated in this paper. It has been shown that with cathode tip height and its radius of curvature decreasing (?100 nm) the transparency of the potential barrier depends non-linearly on the anode voltage in the Fowler-Nordheim coordinates when the cathode tip height decreases from 1000 down to 150 nm. To obtain a measurable autoemission current, work function must not exceed the uniform field’s potential drop between cathode top and its base. Deduced is the analytic formula for the electric field potential that extends approximation features for real cathodes shapes and enables more accurate electric field modeling at the surface.     

Equilibrium solutions for partially immersed relativistic electron beams

The equations relating the beam radius and axial electron velocity to easily measurable external beam parameters are developed for solid, relativistic beams. The beam parameters are tunnel voltage, beam current, axial magnetic field, cathode magnetic field, tunnel radius, and cathode radius. The equations are sufficiently complex to warrant the use of a digital computer if many cases are to be evaluated. Error indicators are formulated to prevent use of the relations beyond their range of validity. The equilibrium solutions for relativistic electron beams from unshielded cathodes show that the required magnetic focusing field is lower than that computed from nonrelativistic formulas. The angular magnetic field produced by the beam itself aids in focusing the electrons. The potential depression due to space charge is analyzed. Correction curves are given which allow the use of nonrelativistic equations in predicting equilibrium behavior. The maximum possible microperveance of relativistic beams is shown to be lower than the classical value of 25.4.     

碳纳米管场发射显示器中栅极技术的研究

碳纳米管场发射显示器件的研究已在各个国家开展了许多年,但仍然有很多的问题亟待解决,如碳纳米管作为阴极发射材料的发射均匀性、开启电场、栅极结构的制作、荧光屏制作、真空封装等困难。本文研究了碳纳米管场发射器件的几种结构、特性及其制作工艺,重点阐述了前栅极结构碳纳米管场发射显示器件中在栅极制作和阴极材料装配的瓶颈,并提出了一种栅极制作和阴极保护的方法,并运用此方法在实验室制作了三极结构器件进行验证,有效地解决了制作前栅极结构的困难,为制作大面积碳纳米管场发射显示屏提供了可行性方案。     

Laser photoelectron sources of high apparent brightness

By focusing an ultraviolet laser beam to a small spot on an appropriately shaped cathode, one can obtain photoelectron beams of 10⁶A . cm^-1. sr^-1brightness. Such a continuous electron source may be useful in electron beam lithography and other applications. Calculations of current densities, brightness, and emitter temperature rises are presented.     

非相干叠加激光发射系统光学设计

介绍了一种适用于三束激光非相干叠加聚焦的新型激光发射光学系统,工作波长1 080 nm,全视场角0.6。系统为离轴两镜反射结构,对三束紧密排列的激光光束进行扩束聚焦,系统主镜为口径303 mm的椭球面反射镜,系统像质接近衍射极限,并且可以通过控制次镜轴向位置调焦适应不同目标距离。计算了叠加后的激光光斑的功率密度分布和环围功率曲线,设计在目标距离1 000 m时叠加光斑半径9 mm内的环围功率大于95%,此激光发射系统结构简单,长径比小,聚焦质量满足使用需求,激光光斑能量得到有效叠加。     

用双平凸薄透镜组聚焦高斯激光束

为了研究高斯激光束经过一种双平凸薄透镜组构成的复合光学系统的聚焦特性,采用矩阵光学方法,得到了高斯激光束经复合光学系统聚焦后光斑半径和像距的计算公式,结合数值计算分析了系统中各参量的变化对复合光学系统的稳定性和束腰处光斑半径的影响,并进一步讨论了高斯激光束经复合光学系统的聚焦特性。结果表明,通过控制各相关参量的取值,复合光学系统会比较稳定,能够获得较小的光斑半径;并通过实验测量,实现了聚焦半径约为2μm的突破,证明了理论分析的正确性。该研究为全固态激光器进一步的实验设计提供了依据。     

均匀磁聚焦和周期磁聚焦部分屏蔽流过渡区的设计

本文叙述均匀磁聚焦和周期磁聚焦部分屏蔽流过渡区设计的一种方法,指出对于阳极电位与慢波线电位不同的电子光学系统,以及这两个电位虽然相同,但导流系数大,阳极孔效应严重的电子光学系统,它们的过渡区的设计,必须采用非等位空间中的傍轴电子轨迹方程。并对用部分屏蔽流周期磁聚焦的电子光学系统,电子枪区中的电子轨迹与磁力线重合的问题提出一些看法。     

增大Bessel光束无衍射距离的凹透镜系统

根据传统轴棱锥法产生Bessel光束的原理和凹透镜的几何光学效应,设计并模拟了一套提高Bessel光无衍射距离的光学系统。利用凹透镜的发散特性,将其分别放置在轴棱锥的前方与后方,使用Math CAD软件进行模拟并与传统轴棱锥法进行比较,得出结论:在轴棱锥前方放置凹透镜使Bessel光的无衍射距离从244 mm增大至638 mm,同时增大中心光斑半径。在轴棱锥后方放置凹透镜使Bessel光的无衍射距离从244 mm增大至406 mm。使用He-Ne激光作为光源进行实验验证,实验结果与理论分析及仿真模拟基本一致。可根据实际要求选择凹透镜的曲率半径和位置,得到无衍射距离较大、质量较高的Bessel光束。     

Influence of space charge on the Langmuir limit for focused electron beams

A theoretical investigation of the validity of Langmuir's expression for the limiting current density in a focused electron beam when space-charge forces are significant was carried out by computing the performance of a series of simple electron tubes, each consisting of a Pierce gun coupled by a thin lens to an equipotential drift space. The analyses show that, while the cathode current density and the peak current density in the spot are related, they are not directly proportional as stated in Langmuir's expression which, therefore, does not give an accurate prediction of the current density that can be obtained in the spot. The dimensions of the tubes were chosen such that this conclusion is also valid in the case of television picture tubes. It is also shown that thermal velocities have only a minor influence on the lens strengths required to focus beams, and that the focused spots havea Gaussian distribution of current density even though the emission density in a Pierce gun is uniform.