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1.
研制了一台集低能电子点源显微镜和场发射显微镜于一体的设备。研制的过程中,解决了包括超高真空的获得,外界振动的隔离,爬行器及其控制电路的设计,场发射电流-电压自动测量,超高真空换样等一系列问题。利用该设备,获得了放大倍数大于10^4的投影像,并且测量了单根多壁碳纳米管的场发射特性。  相似文献   

2.
高分辨扫描电子显微学   总被引:1,自引:0,他引:1  
本文区分了三种扫描电镜.即普通电子枪扫描电镜.场发射电子枪扫描电镜以及场发射枪低象差物镜扫描电镜;指出.了后两种扫描电镜对高分辨扫描电子显微学的重要意义。详细评述了高分辨扫描电子显微学中的电子范围的概念,二次电子的发射特性.二次电子象中所包含的信息以及高分辨率下试样表面导电膜的喷涂的要求和方法。  相似文献   

3.
碳纳米管场致发射特性的研究   总被引:2,自引:0,他引:2  
详细论述了碳纳米管的场致发射特性,包括开启电场、阈值电场、发射电流密度、发射电流的稳定性及场发射电子能量分布等;阐述了场发射的机制;分析了发射特性与其几何结构、吸附态及尖端缺陷等因素的关系;并简要介绍了碳纳米管场发射特性在平板显示领域中的实际应用。  相似文献   

4.
场发射俄歇电子能谱显微分析   总被引:2,自引:1,他引:1  
场发射俄歇电子能谱的显微分析是一项新的分析技术,可对微尺度样品进行点、线、面的元素组分及元素化学态分析。本文简要介绍这项新技术的功能原理和在微电子器件检测等方面的具体应用。  相似文献   

5.
采用丙酮、异丙醇、丙酮/无水乙醇混合溶液3种不同的分散剂,利用电泳沉积法在硅基底上制备了碳纳米管(CNTs)薄膜;采用超景深光学显微镜和电子显微镜观察了不同薄膜的表面形貌,并在高真空中对碳纳米管薄膜阴极进行了场发射特性测试。结果表明:以异丙醇作分散剂制备的CNTs薄膜表面均匀连续,场发射性能较好,开启电场和阈值电场分别为0.188V.μm-1和2.8V.μm-1。  相似文献   

6.
采用多靶磁控溅射技术制备了钛掺杂类金刚石(Ti-DLC)薄膜,并在不同温度(300,350,400℃)下进行了热处理,研究了热处理温度对薄膜微观结构、成分、能带结构以及场发射性能的影响。结果表明:与热处理前的相比,300℃热处理后Ti-DLC薄膜中sp2-C团簇相对含量增大,光学带隙最小,开启场强最低,为5.43 V·μcm-1,场发射性能最好;当热处理温度高于300℃时,薄膜的DLC含量减少,同时生成大量TiO2,光学带隙增加,薄膜开启场强增大,场发射性能变差;薄膜的场发射电流基本不受热处理温度的影响。  相似文献   

7.
6月16日,清华大学电子能谱实验室及电子显微镜实验室被科技部正式批准为国家大型科学仪器中心。其中,以纳米扫描俄歇系统为核心仪器,依托清华建设的能谱中心正式命名为北京电子能谱中心;以300kV配有物镜球差矫正器的场发射枪分析型透射电子显微镜为核心、依托清华建设的电子显微镜中心正式命名为北京电子显微镜中心。  相似文献   

8.
论述了场发射推进器(FEEP)的原理、结构和研究现状,并阐述了开展该研究需要解决的关键技术。分析认为FEEP是一种先进的微牛级电推进器,特别适合于微型航天器的姿态控制、阻力补偿以及星座编队飞行。  相似文献   

9.
本文介绍由场发射环境扫描电镜和高性能阴极荧光谱仪构成的联合分析系统。该系统在图像质量、图像空间分辨、阴极荧光成像及光谱分析等方面具有优越的性能。利用这一系统对氮化物半导体材料的微观特征、器件结构和光学性能的相互关系进行研究,获得许多有意义的结果。  相似文献   

10.
用有限元方法计算X光源场发射阴极电流   总被引:1,自引:0,他引:1  
针对场致发射阵列建立了有效的三维有限元模型来分析单个尖锥的发射电流.考虑到场致发射阵列的周期性和尖锥的轴对称性,仅对一个尖锥单元的1/4进行分析.对模型的表面施加电压边界条件,计算得到尖锥表面电场强度分布,电场强度在尖锥顶点最强,场发射电流在此处也最强.由Fowler-Nordheim函数可得到尖锥表面的场致发射电流密度分布,对整个尖锥表面进行积分后得到了单个尖锥的场致发射电流约为7μA.计算了在100V门电压下不同顶端半径的场致发射电流.结果显示,场发射对顶端半径有很强的依赖性.计算了100个顶端半径为8nm的尖锥在不同门电压下的总场致发射电流,发射电流与开启电压与实际测量值符合得很好.  相似文献   

11.
We introduce a novel scanning projection field emission microscope (SPFEM) designed to study flat broad-area field emission cathodes. The instrument merges capabilities of measuring the electron field emission current from an individual emitting site and genuine projection of electrons onto a luminescent screen. This is achieved by an optimized shape of the anode probe having a 0.04 mm aperture which generates an uniform macroscopic electric field across the investigated area of the cathode. This fact also enables presentation of the relation between the current density and the applied electric field. The magnification of the electron-optical system alone was calculated by computational modeling for some cathode-probe distances and for some voltages. The unique SPFEM performance is demonstrated on smooth sulfur-doped nanodiamond films synthesized on molybdenum substrates.  相似文献   

12.
Detonation carbon materials (DCM) composed of non-equilibrium nano-structures show the low-threshold field emission (LTFE). These materials have forward-looking application especially due to high reproducibility of the LTFE-phenomenon on a surface of emitter, where the emitting centers are homogeneously distributed. In this paper we link the effect of LTFE to the nature of the corresponding wave functions based on the experiment results obtained for DCM by the field effect on electrolytes. As we had shown before DCM had been described by an ultra-relativistic dispersion function with extremely small effective mass of electrons and the size-quantization effect had been observed in DCM at even room temperature.Our results based on emission and electrolyte technics of the field-effect measurements in DCM along with modern observations of the field emission in strong electric fields allowed to propose a new resonance transmission model for LTFE-phenomenon, which is alternative to most widely discussed models based on the field-enhancing factors or barrier-lowering mechanisms.  相似文献   

13.
Zhang Y  Du JL  Xu JH  Deng SZ  Xu NS  Chen J 《Ultramicroscopy》2011,111(6):426-430
Carbon nanotube (CNT) has excellent field emission characteristics and could play as a good cold cathode in the application of vacuum electronic devices. However, the practical application faces a big obstacle regarding current fluctuation and deterioration of the CNT cathode. In this research, the formation of amorphous carbon (ac) layer between the CNT film and the substrate, and the effect of the existence of this layer on field emission stability of the CNT film are studied. The formation of the ac layer could be controlled by adjustment of growth temperature and hydrocarbon flow rate. The field emission character and current stability of the CNT film without ac layer are better than those of the CNT film with ac layer. The results attribute to the ac layer a thermal disequilibrium state under high current level. Moreover, adhesion capacity of the CNT film without ac layer is also better than that with the ac layer. It is concluded that the ac layer between the CNT film and substrate is a key factor in the stability of field emission characteristics and should be eliminated before applications.  相似文献   

14.
The overall performance of any electron microscope is to a great extent determined by the electron source. For example, the current acceptance of the STEM concept is due to the stimulation provided by field emission sources, which made it possible to image single atoms in the STEM. The field emission source remains the electron source with the highest brightness and the lowest energy spread. As a consequence, considerable research and engineering work has been and is still being conducted in a number of important areas. These areas include: (i) the mechanisms which determine the beam current stability; (ii) the electron-electron interactions which lead to beam spreading and an increase of the energy spread; (iii) various types of emitters such as bare tungsten tips, oxygen processed tips, zirconium coated tips, carbon emitters, carbon coated tungsten emitters and even solid state emitters; (iv) the lifetime limiting factors, e.g. inclusions, ion bombardment and flashovers effects; (v) different types of optical systems for field emission guns, e.g. choice of magnetic and/or electrostatic lenses at high voltage potential in UHV systems, and special magnetic lenses just below the anode; (vi) field emission guns operating at higher kV's, up to 1·6 MeV. Because analytical work in the smallest possible volumes is a growing area of scientific interest, the demand for field emission sources which are reliable, easy to operate and stable will continue.  相似文献   

15.
Using field emission and scanning electron microscopy we have studied the influence of strong electric fields on the thermally induced growth behaviour of field emission tips. For smaller fields (i.e. smaller than needed for a satisfactory field emission image) we observe an enlargement of low-index faces, which for higher fields develops into a building-up of micro-structures and roughening on the initially spherical part of the tip surface. In an intermediate state only the region near the (111) directions contributes to the field emission pattern. For the highest fields employed the results indicate the growth of local protrusions preferentially near (100) faces. Our results show that in scanning tunnelling microscopy W(111) tips should be superior to the commonly used W(110) tips.  相似文献   

16.
We give an account of the development of electron emission imaging and the photoelectron emission process. We then describe a particular combination of photoelectron emission microscopy and photoelectron spectroscopy which we call photoelectron spectromicroscopy. This is achieved using a very strong, divergent magnetic field to define electron trajectories without the use of electron optical focusing. It is thus possible to produce electron images of the surfaces of three-dimensional objects using low energy photoelectrons in which the image contrast is dependent upon, among other things, the yield and energy distribution functions. The various image contrast mechanisms which apply are outlined with illustrative examples. Techniques for energy analysis of the photoelectron image are described and examples of the photoelectron spectra of different regions of the surface of an object presented. Electron images produced by metastable atoms and slow ions are also discussed. The use of the magnetic field introduces the opportunity for a number of novel techniques which will be described.  相似文献   

17.
声发射技术在磨削加工监测中的应用   总被引:14,自引:0,他引:14  
近十几年来,声发射技术在机械加工方面获得了普遍的关注,其理论与方法已成为现代制造系统用来监测加工过程状态的一个重要的研究领域。文中概述了声发射(AE)技术的基本原理,讨论了磨削过程中声发射源产生机理,介绍了声发射技术在磨削加工监测方面的研究进展,简要指出了研究中存在的主要问题和发展方向。  相似文献   

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