共查询到19条相似文献,搜索用时 140 毫秒
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利用场发射显微镜(FEM)和四极质谱计分别研究了经过热处理的单壁碳纳米管的场发射图像和热处理过程中样品脱附的残气质谱.当热处理温度达到1000℃左右时得到了单壁碳纳米管的场发射像,此像可能是顶端开口的单根(16,0)锯齿形单壁碳纳米管的具有原子可分辨的场发射图像.四极质谱分析结果表明,在此温度范围W针尖晶粒间隙中有O原子和C原子释放出来.它们对单壁碳纳米管顶端的修饰是我们能观察到这些碳纳米管场发射像的可能原因.
关键词:
单壁碳纳米管(SWCNTs)
场发射显微镜(FEM)
四极质谱 相似文献
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研究了Ar离子束轰击及温度对多壁碳纳米管阵列场发射性能的影响.经Ar离子轰击35min后,发现阵列顶端的Fe催化剂颗粒明显减少,弯曲的顶部被轰击掉,使碳纳米管的场发射电流明显减小而场发射像无明显改变.温度的增加引起碳纳米管的场发射电流也随之增加.还研 究了在透明阳极技术中涂在阳极的荧光粉对场发射电流的影响.对同一碳纳米管阵列样品,发现涂有荧光粉的透明阳极使测量到的场发射电流大幅度减小,只是未涂荧光粉阳极电流的 1/30左右.直接用二氧化锡导电膜作阳极时,测得样品的开启场强为1.0V/μm.沉积了荧光粉的二
关键词:
多壁碳纳米管
场发射 相似文献
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结合电泳沉积和激光纳米焊接技术在常温下成功制备了铝基单壁碳纳米管(SWCNTs-Al)薄膜。首先,将单壁碳纳米管电泳沉积到铝片基底上,再使用皮秒脉冲激光构建二者的可靠连接。对SWCNTsAl薄膜进行场发射性能测试,开启电压从焊接前的5.1V/μm降低到2.1V/μm,发射电流密度显著提高且更加稳定。这主要是激光纳米焊接后界面接触阻抗减小,场致电子发射更容易实现的结果。基于SWCNTs-Al薄膜的表面形貌图和场发射性能测试结果,确定了最优的激光纳米焊接参数。 相似文献
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报道了在较大发射面积上获得较大场发射电流的碳纳米管场发射阴极。为了加强场发射电流,在丝网印刷浆料中增加一种金属纳米颗粒,金属颗粒增强了碳纳米管发射体和衬底的接触,提高碳纳米管和衬底的粘附作用。利用改进后的丝网印刷方法制备了大电流碳纳米管场发射阴极,测得最大发射电流为68.0 mA,阴极有效发射面积约1.1 mm2,发射电流密度约6.2 A/cm2;并成功将改进方法制备的大电流场发射碳纳米管阴极应用于场发射真空器件原型。实验证明这种具有较大发射电流和较大发射电流密度的场发射能够满足部分大功率电子器件的需求。收稿日期:; 修订日期: 相似文献
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采用高温热解法在860℃分别制备出了碳、碳氮和硼碳氮纳米管,提纯后利用丝网印刷工艺分别将它们制备成薄膜,并测试了它们的场发射性能.结果表明:碳纳米管、碳氮纳米管和硼碳氮纳米管薄膜的开启电场分别为2.22,1.1和4.4V/μm,当电场增加到5.7V/μm时,它们的电流密度分别达到1400,3000μA/cm2和小于50μA/cm2.碳和碳氮纳米管薄膜的场增强因子分别为10062和11521.可见,碳氮纳米管的场发射性能优于碳纳米管,而硼碳氮纳米管的场发射性能比前两者要差.解释了这三种纳米管场发射性能差别的原因.
关键词:
碳纳米管
碳氮纳米管
硼碳氮纳米管
场发射 相似文献
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Electrodeposition of aligned ZnO sheet array on ITO substrate and their field emission characteristics 下载免费PDF全文
ZnO sheet array was fabricated by a simple electrodeposition method on the transparent ITO substrate at a temperature of about 60℃. The field emission properties of the ZnO sheet array were investigated. The fluctuation of the field emission current is less than 5% over several hours. The Fowler Nordheim curves with a roughly linear characteristic were obtained by analysing the current density and the intensity of the electrical field. The results prove that such a simple electrochemical method can potentially meet the demands on the production of cold cathodes for field emission display.[第一段] 相似文献
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Field electron emission (FE) is a quantum tunneling process in which electrons are injected from materials (usually metals)
into a vacuum under the influence of an applied electric field. In order to obtain usable electron current, the conventional
way is to increase the local field at the surface of an emitter. For a plane metal emitter with a typical work function of
5 eV, an applied field of over 1 000 V/μm is needed to obtain a significant current. The high working field (and/or the voltage
between the electrodes) has been the bottleneck for many applications of the FE technique. Since the 1960s, enormous effort
has been devoted to reduce the working macroscopic field (voltage). A widely adopted idea is to sharpen the emitters to get
a large surface field enhancement. The materials of emitters should have good electronic conductivity, high melting points,
good chemical inertness, and high mechanical stiffness. Carbon nanotubes (CNTs) are built with such needed properties. As
a quasi-one-dimensional material, the CNT is expected to have a large surface field enhancement factor. The experiments have
proved the excellent FE performance of CNTs. The turn-on field (the macroscopic field for obtaining a density of 10 μA/cm2) of CNT based emitters can be as low as 1 V/μm. However, this turn-on field is too good to be explained by conventional theory.
There are other observations, such as the non-linear Fowler-Nordheim plot and multi-peaks field emission energy distribution
spectra, indicating that the field enhancement is not the only story in the FE of CNTs. Since the discovery of CNTs, people
have employed more serious quantum mechanical methods, including the electronic band theory, tight-binding theory, scattering
theory and density function theory, to investigate FE of CNTs. A few theoretical models have been developed at the same time.
The multi-walled carbon nanotubes (MWCNTs) should be assembled with a sharp metal needle of nano-scale radius, for which the
FE mechanism is more or less clear. Although MWCNTs are more common in present FE applications, the single-walled carbon nanotubes
(SWCNTs) are more interesting in the theoretical point of view since the SWCNTs have unique atomic structures and electronic
properties. It would be very interesting if people can predict the behavior of the well-defined SWCNTs quantitatively (for
MWCNTs, this is currently impossible). The FE as a tunneling process is sensitive to the apex-vacuum potential barrier of
CNTs. On the other hand, the barrier could be significantly altered by the redistribution of excessive charges in the micrometer
long SWCNTs, which have only one layer of carbon atoms. Therefore, the conventional theories based upon the hypothesis of
fixed potential (work function) would not be valid in this quasi-one-dimensional system. In this review, we shall focus on
the mechanism that would be responsible for the superior field emission characteristics of CNTs. We shall introduce a multi-scale
simulation algorithm that deals with the entire carbon nanotube as well as the substrate as a whole. The simulation for (5,
5) capped SWCNTs with lengths in the order of micrometers is given as an example. The results show that the field dependence
of the apex-vacuum electron potential barrier of a long carbon nanotube is a more pronounced effect, besides the local field
enhancement phenomenon. 相似文献
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热处理对纳米金刚石涂层场发射性能的影响 总被引:4,自引:4,他引:0
用旋涂法在金属钛衬底上涂敷纳米金刚石,经过适当的热处理形成金刚石涂层与金属钛衬底的化学键合,即形成衬底与涂层之间的过渡层,从而为纳米金刚石颗粒提供电子,使其成为有效的发射体。用扫描电镜、原子力显微镜、X射线衍射和拉曼散射等手段分析了温度对键合效果以及场发射性能的影响,温度过高或过低都不利于提高纳米金刚石涂层的场发射性能,只有在700℃左右对样品进行热处理,才能得到较好的键合状态。改变涂膜时旋涂的次数以获得不同涂层厚度的样品,对其在700℃的相同温度下进行热处理,发现涂层过厚或过薄都不利于样品发射性能的提高。旋涂9次并于700℃热处理的样品具有较好的场发射性能,其发射阈值场强可达4.6V/μm,而15.3V/μm场强下的电流密度为59.7μA/cm2。 相似文献
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Debasish Ghosh Pradip Ghosh Mohd Zamri Yusop Masaki Tanemura Yasuhiko Hayashi Tetsuo Tsuchiya Tomohiko Nakajima 《固体物理学:研究快报》2012,6(7):303-305
A fully transparent and flexible field emission device (FED) has been demonstrated. Single‐walled carbon nanotubes (SWCNTs) coated on arylite substrate were used as electron emitters for the FED and a novel metavanadate phosphor coated on the SWCNTs/arylite film was used as transparent and flexible screen. The SWCNTs/arylite based emitters and the SWCNTs/arylite/metal‐vanadate‐based phosphor showed a transmittance value of 92.6% and 54%, respectively. The assembled device also showed satisfactory transparency and flexibility as well as producing significant current. Metavanadate phosphor is considered to be an excellent candidate due to its superior luminescence properties and easy fabrication onto transparent and flexible conductive substrate at room temperature while retaining reasonable transparency of the substrate. Thus, its transparency and flexibility will open the door to next‐generation FEDs. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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碳纳米管(Carbon Nanotubes,CNTs)场发射平面显示器(Field Emission Display,FED)与其他显示器比较显示了其独特优点,被认为是未来理想的平面显示器之一。碳纳米管阴极作为器件的核心部分,其性能的好坏直接影响显示器的性能。针对30~60英寸(76.2~152.4cm)大屏幕显示器所用的厚膜工艺,即采用丝网印刷法制备了碳纳米管阴极阵列,研究了化学气相沉积法在不同温度下生长的CNTs的场发射电流-电压特性,找到了适合FED用碳纳米管的最佳生长温度。结果表明生长温度越高(750℃),CNTs场发射性能越好。并用荧光粉阳极测试这些CNTs的场发射发光显示效果,验证了上述结论。 相似文献
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Electron emission properties of single-walled carbon nanotubes (SWCNTs) assembled on a tungsten tip were investigated using field emission microscopy (FEM). The transmission electron microscopy (TEM) micrograph confirmed the existence of an SWCNT bundle on the W tip. Under appropriate experimental conditions,a series of FEM patterns with atomic resolution were obtained. These patterns arose possibly from the field emission of the open end of an individual (16,0) SWCNT protruding from the SWCNT bundle. The magnification factor and the resolution under our experimental conditions were calculated theoretically. If the value of the compression factor β was set at β= 1.76, the calculated value of the magnification factor was in agreement with the measured value. The resolving powerof FEM was determined by the resolution equation given by Gomer. The resolutionof 0.277 nm could be achieved under the typical electric field of 5.0×107 V/cm, which was close to the interatomic separation 0.246 nm between carbon atoms along the zigzag edge at the open end for the (16, 0) SWCNT. Consequently, our experimental results were further supported by our theoretical calculation. 相似文献
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Annealing effect on structure and green emission of ZnO nanopowder by decomposing precursors 下载免费PDF全文
ZnO nanopowder is successfully synthesized by annealing
the precursors in oxygen gas using the chemical precipitation method.
Structural and optical properties of thus synthesized ZnO nanopowder
are characterized by scanning electron microscopy (SEM) and
photoluminescence (PL). The morphology of ZnO nanopowders evolves
from nanorod to cobble as annealing temperature increases from 500
to 1000~\du, while spiral structures are observed in the samples
annealed at 900 and 1000~\du. The PL spectra of ZnO nanopowder
consist of largely green and yellow emission bands. The green
emission from ZnO nanopowder depends strongly on the annealing
temperature with a peak intensity at a temperature lower than 800~℃
while the yellow emission is associated with interstitial oxygen
\rm O_\i. 相似文献