W[111]场发射尖端的制作与使用

本文报道w[111]场发射尖端的制作,使用条件以及尖端的闪烁和重建。从实验得到其正常工作范围是尖端曲率半径在0.9～1.2×10～(-5)cm;第一阳极电位V_1在2～2.5KV之间。闪烁电压约3～4伏,时间0.5～2秒;w[111]尖端重建条件为尖端表面电场强度必须大于3×10～7V/cm,加热电压为30伏,时间1×10～(-2)秒。了解这些情况对场发射电子枪的正确使用和维护无疑是重要的,具有实用意义。     

尖端场发射系统形状系数β的计算

目前利用场发射原理,制成的场发射电子枪(FEG)和液态金属离子源(LMLS),因具有束斑小,亮度高,寿命长和能量分散小等特点,将为人们所关注。现在FEG已被广泛应用于SEM,STEM,电子束曝光和俄歇电子谱仪等各种大型电子光学仪器;LMIS也在离子注入,离子束刻蚀,离子束曝光和二次离子谱仪等表面分析仪器和表面微加工等技术中获得广泛应用。在FEG和LMIS的制作和应用中,仍有许多承待解决或改进的问题。较精确的计算系统的形状系数β值就是其中之一。我们知道,不论是FEG的发射电子流还是LMIS的发射离子流都是由发射尖端的电场强度ε决定的。而ε首先由所加电压u_0决定,其次与尖端的几何形状及尖端到吸取极的距离有关。由于     

Ta场发射特性的实验研究

本文报道了钽(Ta)场发射尖端的制作方法和场发射特性的实验结果。并与单晶钨(W〔111〕)比较,发现Ta的场发射特性不仅与W〔111〕很相似,而且还别具自己特点。特别是能在6.6×10~(-8)帕(5×10~(-8)托)较低真空下稳定的工作。表明Ta可望成为一种较理想的场发射材料,具有广泛应用和开发前景。     

高分辨率热场发射显微镜(HRTFEM)

1937年E.W.Müller[1]发明了场发射显微镜(FEM),直到最近[2],人们一直认为FEM的分辨力只能在2nm上下,因而不能像场离子显微镜(FIM)那样可以分辨原子[3]。我们认为FEM的分辨力在理论上可以接近0.1nm,2nm并不是FEM的理论极限,而是人们在实际上一直未能用FEM所超过的水平。其原因在于人们对FEM成像中空间电荷的影响认识不足。众所周知,场发射电流密度比热发射电流密度大几个数量级,因而场发射电流在尖端前面所形成的空间电荷比较严重。在FEM中,图像是由尖端上电子云分布的投影形成的,空间电荷的存在必然干扰甚至屏蔽表面电子云的分…     

GaAs[100]衬底的择优腐蚀

(一)引言 GaAs是闪锌矿结构,在[111]方向有极性,当选择适当的择优腐蚀液时,各晶面的腐蚀速度有[110]≥B[111]≥[100]>A[111]关系。A[111]面是难以被腐蚀的。因此,它对腐蚀图形起重要作用,利用这个特点可以设计和制造各种形状的新器件。本文介绍了     

计算机控制的探孔场发射显微镜系统

由Apple Ⅱ微机控制的探孔场发射显微镜系统已研制成功,并可用其测量单个晶面的逸出功。被探测微区的探孔电流由探测荧光屏,光电倍增管和电流放大器的联合体进行测量。观察屏电压(阳极电压)由D/A转换器调节。场发射体总电流和探孔电流数据由A/D转换器采集。测量系统校准后,用BASIC语言编写的程序处理所测得的数据和计算Fowler-Nordheim图参数,从而得到被测的单个晶面的逸出功。用此系统已测得清洁的W(100)和W(111)面逸出功分别为4.67eV和4.45eV。     

用热壁外延技术在CdTe衬底上生长CdTe薄膜

利用热壁外延技术在CdTe衬底的(111)A面和B面生长了CdTe薄膜。源温度和衬底温度分别在670～800℃和600～760℃之间,生长速率为0.8～1.3μm/h。X射线衍射和荧光分析表明,CdTe外延层为[111]方向生长的高纯单晶薄膜,外延层表面组分和纵向组分均勺;回摆曲线峰半高宽的典型值为1.38′,表明外延层为高质量的CdTe单晶膜。     

Cleaning method of InSb [111] B of n-InSb [111] A/B for the growth of epitaxial layers by liquid phase epitaxy

The crystal structure of InSb[111]A/B surfaces shows that this structure is polarized.This means that the surfaces of InSb[111]A and InSb[111]B contain two different crystallized directions and they have different physical and chemical properties.Experiments were carried out on the InSb[111]A/B surfaces,showing that tartaric acid etchant could create a very smooth surface on the InSb[111]B without any traces of oxides and etch pit but simultaneously create etch pit on InSb[111]A surfaces.After lapping and polishing,some particles remained on the InSb[111]B surface,they could not be removed easily by standard cleaning process and if these particles remain on the surface of the substrate,the growth layer was not uniform and some island-like regions were observed.The purpose of this work is to remove these particles on the InSb[111]B surface.Some morphology images of both surfaces,InSb[111]A/B,will be presented.     

透射电子显微学的新进展Ⅰ透射电子显微镜及相关部件的发展及应用

本文综述了透射电子显微镜(TEM)及相关部件,即场发射枪(FEG)透射电子显微镜、慢扫描电荷耦合器件(SSCCD)、球差校正器、单色器及高能量分辨率的新一代能量过滤成像系统的发展及应用。商业化的UltraScan 1000 SSCCD的读写速度已达4MHz,接近实时观察图像的目标;已生产出用于TEM和STEM的球差校正器,可把CM200 FEG TEM的球差系数从常规的1．23mm调整至 2mm～-0．05mm之间的任意值;单色器可把肖特基场发射枪发射电子的能量分散从0．6～0．8eV减少至0．04～0．1eV;新一代能量过滤成像系统HR-GIF可把能量分辨率从0．8eV提高至0.05eV。配有单色器、球差校正器、HR-GIF的新一代场发射枪透射电子显微镜可提供亚埃的空间分辨率和亚电子伏特的能量分辨率,为研究物质的原子-电子结构提供了可靠的保证。     

计算场发射系统尖端形状系数的半经验公式

本文提出了一般场发射系统尖端形状系数的计算公式:0.2/[(r0+h)ln(2h/r0)]。用该公式和数值计算法以及D.Selidovkin,W.Swanson和P.Dyke等人提出的相应公式,分别对尖端呈半球形、椭球形、旋转抛物形和双曲形四种场发射系统的值进行了计算和比较。结果表明,用本文的公式所得的值与电子计算机的数值计算结果基本上是一致的。     

细胞质多角体病毒的高分辨成像及其三维重构的初步结果

使用装有液氦冷却的冷冻样品支架的300kV场发射冷冻电子显微镜拍摄了细胞质多角体病毒（CPV），对这些电镜照片的频谱分析显示图像分辨率优于0．6nm。我们的三维重构结果使用了最新设计的图象管理和二十面体重构系统（IMIRS）软件包，这是第一个基于Microsoft Windows平台上运行的冷冻电镜三维重构软件包。从得到的一个初步的CPV三维结构，可以看出CPV是具有T＝1的病毒壳体，它的核心半径为28．5nm，在二十面体的顶点有十二个具有五次对称的突起，使它的半径达到36nm。     

三极场发射电子枪虚源半径的计算

本文在分析形成和影响场发射电子枪（ＦＥＧ）虚源半径各有关因素的基础上，报道了一种计算其值的方法。用该法对一实际ＦＥＧ的虚源半径作了计算，并与实验和著名的球锥面模型进行比较，结果是一致的。表明该法不仅简单且行之有效，具有较大的实用价值。     

Development of battery charging system for the FE gun system of HVEM

We have developed a reliable and efficient battery-charging system for the field emission (FE) gun system of high voltage electron microscopes, where the operating condition of the whole FE gun system can be controlled and monitored through a bi-directional optical fiber system, and the control and monitoring circuits located on the high potential of 1 MV are driven by rechargeable Ni-Cd batteries. The power transmission from ground to the high potential is performed through filter condenser circuit. Under the condition that the filter condenser current is limited to 0.2 A(rms) (root-mean-square value), it is possible to transmit the maximum power as high as 65 W, which is enough for the daily operation of the FE gun system. The charging circuit has a function of protecting the batteries from over-charging.     

Development of remote control and monitoring system for the FE gun in HVEM

This paper describes a control and monitoring system for the field emission (FE) gun in the high-voltage electron microscope (HVEM), where the whole FE gun system is located inside a pressure vessel and is floated on a high voltage of 1 MV. The operating condition of the FE gun system is controlled and monitored mainly by a bi-directional communication system between ground and high potential through optical fibres. A mechanical driving system by combination of insulator rods and stepping motors is partially used as a control system for FE gun operation. The monitoring system developed here also functions as a safety circuit that detects abnormal situations, such as an abnormal deterioration of vacuum, and protects the FE tip against fatal damage. The fundamental performance of the microscope has been tested for transmission electron microscope (TEM) and scanning TEM operation modes.     

一种电子枪分析设计

设计一种大功率轰击型六硼化镧电子枪。以传热学理论基础和重要结论为依据,得出能减小阴极电子枪热量损失的几个设计与材料选取原则。利用有限元法对轰击型六硼化镧电子枪阴极模型进行热模拟。依据模拟结果设计一种轰击型六硼化镧阴极电子枪,其发射面直径为2.0 mm,当加热功率为80.0 W时,阴极温度达到1 569℃所发射电子束束流密度达到5.55 A/cm2,并且发射稳定、束斑均匀、发散度小,反复暴露于大气后仍能正常工作。     

Low convergent confined-flow Pierce gun for a space TWT

An approach for designing an electron gun for a high efficiency, high linearity space traveling wave tube (TWT), has been presented. A low convergent (<10?:?1) Pierce electron gun of beam perveance 0.43?μP has been designed for a high gain, high linearity and high efficiency C-band 60?W Space TWT using in-house developed two-dimensional FDM based gun and collector simulation code PIERCE. In this gun, the first anode (isolated from the ground anode) has been kept nearly 100?V above the ground anode to act as an ion barrier for increasing cathode life and to regulate beam current over the lifetime of the tube. An M-type dispenser cathode of diameter 3.20?mm has been used for cathode loading of less than 1.0?A/cm² and heater wattage around 3.0?W. The magnetic focusing with integral-pole-piece barrel assembly and periodic-permanent magnets (PPM) have been designed using in house developed two-dimensional FDM based code SUNMAG. The practical problem of linking requisite cathode flux to the cathode for confined flow of the electron beam with low convergence factor has been sorted out by gradually increasing the PPM magnetic field. The magnetic field has been increased in steps from the gun and over the first five magnets varying from Brillouin field (B _B) value to twice B _B for achieving the electron beam with scalloping less than 10%. Agreements between the simulated results and the experimental results for the beam current and magnetic field profile have been achieved within 8%. The dynamic beam transmission (under rf operation of the tube) has been achieved better than 98% in the tube.     

Chemical and structural analysis of etching residue layers in semiconductor devices with energy filtering transmission electron microscopy

The use of an energy-filtering field emission gun transmission electron microscope (CM30 FEG Ultratwin) allows, apart from imaging morphologies down to nanometer scale, the fast acquisition of high-resolution element distributions. Electrons that have lost energy corresponding to characteristic inner-shell loss edges are used to form the element maps. The production of Ultra Large-Scale Integration (ULSI) devices with dimensions below 0.25 μm requires among others the formation of a multilayer metallization scheme by means of repeatedly applying the deposition and etching of dielectrics and metals. In this work the evolution of the surface chemical species on etched Al lines in a post-etch cleaning process has been investigated by energy filtering transmission electron microscopy, with the aim to understand the role of each process step on the removal of the etching residues.     

Ka波段高压缩比电子光学系统的分析与设计

微波电真空器件向高功率、高频率、宽频带、高效率和小型化方向发展,对电子光学系统的要求也日益增高。文中设计了工作于Ka 波段的扩展互作用速调管(Extended Interaction Klystron, EIK)高压缩比电子枪,利用二维仿真软件E-GUN 和三维仿真软件Opera-3D 对轴对称电子束在均匀永磁聚焦磁场内运动状态进行建模并仿真计算。相关结果表明,在阳极电压25 kV、注电流2.5 A、阴极面电流密度不超过12A/cm2 的条件下,面压缩比约为85,电子注以良好的刚性通过互作用区域。     

TEM场发射枪通信控制技术研究

研究了200kV场发射枪透射电子显微镜（TEM）场发射枪的通信控制原理。上位机PLC采用ModBus协议与下位机200kV场发射枪通信控制板通信,下位机场发射枪通信控制板与电子枪被控对象采用三务总线形式的I^2C协议,基于两种不同协议之间的通信控制,设计了两种协议之间的转换控制模块,实现了上位机PLC和下位机200kV场发射枪电源之间的数据可靠通信,给出了对200kV场发射枪透射电子显微镜场发射枪电源通信控制的软硬件设计。     

Field Emission and Cathodoluminescence of ZnS Hexagonal Pyramids of Zinc Blende Structured Single Crystals

Single‐crystal hexagonal pyramids of zinc blende ZnS are fabricated by facile thermal evaporation in an ammonia atmosphere at 1150 °C. It is found that ZnS pyramids grow along the [111] crystal axis and possess a sharp tip with a diameter of ～10 nm and a micrometer‐sized base. The structural model and growth mechanism are proposed based on crystallographic characteristics. This unique ZnS pyramid structure exhibits a low turn‐on field (2.81 V µm^?1), a high field‐enhancement factor (over 3000), a large field‐emission current density (20 mA cm^?2), and good stability with very small fluctuation (0.9%). These superior field‐emission properties are clearly attributed to the pyramid morphology, with micrometer‐sized bases and nanotips, and high crystallinity. Moreover, a stable UV emission of 337 nm at room temperature is observed and can be ascribed to the band emission of the zinc blende phase. These results suggest that the ZnS hexagonal pyramids can be expected to find promising applications as field emitters and optoelectronic devices.