分散剂对电泳沉积制备碳纳米管薄膜形貌和场发射性能的影响

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。     

基于碳纳米管静态乳腺CT的阴极性能测控平台设计

以碳纳米管作为阴极材料的场致发射X射线源及成像技术是国际上的研究前沿,也是CT技术的重要发展趋势之一。相比传统热电子发射X射线源而言,碳纳米管X射线源具有结构紧凑、高时间分辨率、可编程式发射等优势。为了满足课题中对碳纳米管阴极场发射电流性能的测试与监控需要,在微软公司的Visual Studio 2015开发环境下采用C++作为本程序的编程语言,设计并实现碳纳米管静态乳腺CT的阴极性能测控平台。经测试验证后,本程序的具有操作简便、自动化程度高、界面交互性好等优势。     

低能电子点源显微镜的研制及初步实验结果

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。     

高分辨扫描电子显微学

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。     

碳纳米管薄膜制备及应用研究进展

膜状碳纳米管保留了碳纳米管微观性状,也保留了优异的导电能力。它具有良好的机械性能、独特的形貌与结构特征,在储能电池技术、人工肌肉、智能材料以及电子显示屏中的应用越来越普遍。本文介绍碳纳米管薄膜的特点,对几种碳纳米管薄膜制备方法做了简要介绍说明。通过对当前碳纳米管薄膜几大应用方向如超级电容、柔性电池以及场发射装置等的分析,展示了碳纳米管薄膜的巨大应用潜力。     

碳纳米管能够吸收与发散光波

美国罗切斯特大学的科研人员最近发现 ,碳纳米管具有理想的吸收与发散光波的特性。利用碳纳米管材料的这一新特性 ,未来可望使量子密码技术以及单分子传感器变成现实。科研人员在最新出版的《科学》杂志上发表论文指出 :在室温条件下 ,碳纳米管能够吸收较窄频谱的光波 ,并能稳定性散发还原光波。这意味着碳纳米管具有传输、储存和恢复光波信号的新性能。利用强力聚焦的激光照射碳纳米管 ,研究人员发现 ,碳纳米管能够吸收光波 ,并以新的频谱发射光波 ,这些新频谱携带着反映碳纳米管材料物理特性的信号。进一步的研究表明 ,碳纳米管材料可以还…     

一种基于FFT特征提取定位算法的甚低频仿生水下主动电场定位系统

主动电场定位的思想源自仿生学研究。生物学研究者发现,在没有光线的情况下,弱电鱼能通过感应自身发射电场的变化信息来捕获食物并导航,这种利用自身发射和接收电场来探测、识别、定位物体的能力被称为主动电场定位识别。在建立水下主动电场定位试验平台后,为实现该平台的水下电场定位,在该平台上对甚低频(10 Hz)电场激励下不同水体环境下不同电学特性物体的定位特性进行试验研究;随后,在总结上述特性研究的基础上,提出基于FFT特征提取的水下主动电场定位算法并在该试验平台上实现在不同水体环境中对不同性质物体的精确定位试验。成功提出一种基于FFT特征提取定位算法的甚低频水下主动电场定位原型机,该原型机证明了该方案的水下主动电场定位的可行性和有效性,为该技术为进一步工程应用和相关特性研究提供基础。     

催化剂颗粒对自持放电型碳纳米管气体传感器电极的影响

根据高电场作用下，气体的自持暗放电曲线不同区分气体的方法灵敏度高，不易产生交叉敏感，但是工作电压高，用催化热解法在硅基上生长出垂直于基底的碳纳米管阵列，利用碳纳米管的尖端效应，使得高电场集中在一个微小的区域内（纳米级），从而使得气体导电所需的工作电压大幅度下降，催化热解法生长出的碳纳米管顶端含有催化剂颗粒，当其紧密排列时，形成屏蔽层，减弱了碳纳米管的表面场强，这里，提出三步纯化法，去除了碳纳米管阵列顶端的催化剂颗粒，极大地增强了碳纳米管的表面场强。     

基于碳纳米管的尖端电极对汤生放电型气体传感器特性的影响

研制出不锈钢针尖，特制钨尖，以及在尖端上生长有碳纳米管(CNT)阵列的针尖与钨尖4种尖端电极，分别测试了4种尖端电极的负离子产生量，及其在空气中汤生放电的不同的I—V特性曲线。影响气体放电的因素很多，其中电极形状和材料是极为关键的因素。笔者通过大量的研究，对这4种尖端电极进行了分析和讨论，发现特制钨尖比不锈钢针尖的表面电场强，而在这两种尖端上生长了碳纳米管后，负离子产生量分别提高到原来的3倍，表明其表面电场加强且表面逸出功降低。汤生放电研究发现，选择生长有碳纳米管的特制钨尖作为电极，不仅可以降低气体的放电电压，而且还可以增大极间距，有利于气流的通畅和传感器的恢复。     

碳纳米管在柔性电子器件中的应用研究

碳纳米管由于其独特的电学特性,近些年得到了广泛研究与应用。采用碳纳米管制作而成的电子设备,比碳芯片设备体积更小,速度更快,并且还具备很好的节能有点。随着电子学发展,柔性电子应运而生,在碳纳米管电子特性基础上,详细探讨了碳纳米管在柔性应变器、柔性导线以及超级电容器等电子器件中应用进展,最后指出了碳纳米管在柔性电子器件领域中的应用前景和趋势。     

Visualization of individual emission sites on flat broad-area field emission cathodes

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.     

用有限元方法计算X光源场发射阴极电流

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.     

Modeling and calculation of field emission enhancement factor for carbon nanotubes array

To estimate the apex field enhancement factor associated with carbon nanotubes (CNTs) array on a planar cathode surface, the image model of floated sphere between parallel anode and cathode plates was proposed. Firstly, the field enhancement factor of individual CNT was given as the following expression, beta0=h/rho+3.5, where h is the height and rho is the radius of CNTs. Then the field enhancement factor of CNTs array was discussed and the above expression was modified to be beta=h/rho+3.5-W, in which W is the function of the intertube distance R and represents the coulomb field interaction between the CNTs. All results show that the intertube distance of CNTs array critically affects the field emission. When the intertube distance is less than the height of tube, the field enhancement factor will decrease rapidly with decreasing the intertube distance. According to the calculated results and considering the field emission current density, the filed emission is optimal theoretically when the intertube distance is comparable with the height of CNTs.     

The effect of amorphous carbon layer on the field emission characteristics of carbon nanotube film

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.     

Improving the emission characteristics of a carbon nanotube cathode in an aging process

Aging of the field emission performance of the printed carbon nanotubes (CNTs) cathode is studied. A continuous increase of the field emission current as well as the density of field emission sites under a constant voltage is observed. It is revealed that the resistant heating may play an important role in the activation of the potential emitters during the aging process. A technique of activating the printed CNT cathode with an aging process is suggested. F-N curves before and after the aging processes are analyzed and it is revealed that the effective emission area increases during the aging process.     

LEO SUPRA系列热场发射扫描电子显微镜

本文介绍LEOSUPRA系列热场发射扫描电子显微镜的性能及特点 ,主要包括肖特基场发射电子源、电子光学系统以及检测器等。     

Low-threshold field emission from carbon nano-clusters

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.     

热处理对钛掺杂类金刚石薄膜场发射性能的影响

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·...