Brightness and coherence of electron beam emitted from a multi-wall carbon nanotube

1. 一种表面清洁的带帽多壁碳纳米管的场发射模式由六个五边形环组成，对应于位于尖端的五边形。为了评估单个五边形作为电子源的光学特性，利用探针-空穴型场发射显微镜测量了单个清洁五边形的I-V特性和角电流密度。在53nA的发射电流下，从角电流密度和五边形几何尺寸估计的亮度降低达到~ 5.6×109 Am-2sr-1 V-1。这个值比Jonge等人报道的单个多壁碳纳米管场发射器的值高出一个数量级或更多。一种表面清洁的带帽多壁碳纳米管的场发射模式由六个五边形环组成，这些五边形环对应于位于尖端的五边形。在相邻五边形的边界上也可以观察到一条或几条明亮的条纹。条纹的间距与加速电压的平方根成反比。即根据杨氏干涉方程，间距随发射电子的波长而变化。条纹的可见性随着加速电压的增加而增加，这可以用虚拟源尺寸的概念成功地解释。这些实验结果表明，这些条纹只不过是杨氏干涉条纹，相邻的五边形表现为双狭缝。提出了用电子双棱镜直接观测电磁微场的方法。这种干涉法比三波干涉法更简单有效。

1. A capped multiwall carbon nanotube with a clean surface gives filed emission patterns consisting of six pentagonal rings corresponding to pentagons located at the tip. To evaluate the optical properties of a single pentagon as an electron source, the I-V characteristics and angular current densities for a single clean pentagon have been measured, by probe-hole-type field emission microscopy. Reduced brightness estimated from the angular current density and the geometrical size of the pentagon reached 〜5.6×109 Am-2sr-1 V-1 at an emission current of 53nA. This value is one order of magnitude or more higher than that of an individual multiwall carbon nanotube field emitter reported by Jonge et al.2. A capped multiwall carbon nanotube with clean surface gives field emission patterns consisting six pentagonal rings which correspond to pentagons located at the tip end. One or a few bright streaks are also observed at the boundaries of neighboring pentagons. The spacing of streaks is inversely proportional to the square root of the accelerating voltage. Namely, the spacing changes with the wave length of emitted electrons according to Young's interference equation. The visibility of streaks increased with the accelerating voltage, which can be explained successfully in terms of a concept of a virtual source size. These experimental results suggest that the streaks are no more than Young's interference fringes for which the adjacent pentagons behave as double slits.3. The direct observation method of electromagnetic micro-fields with an electron biprism is developed. This interference method is simpler and more effective than the three-wave interference one.