Field emission properties from Carbon Nanotube
Carbon nanotubes (CNTs) have been considered as a good field emission material due to their unique morphology and excellent properties. Until now, there were many reports on field emission properties from CNTs1-4. Field emission properties of CNTs revealed much higher emission current and lower turn-on field than those of conventional metal tips or silicon tips. In this work, we report field emission properties of CNTs dependent on the diameter, crystallinity, alignment and a screening effect. We also fabricated thin multi-walled CNT field emitters using a new filtration-transfer method. The CNT emitter fabricated by the filtration-transfer method shows that the very high emission current density of 500 mA/cm2 was achieved by CNT field emitters by using the filtration-transfer method.
Field emitters can be classified according to the emitter shape, one is a planar emitter and the other is a point emitter. The planar emitter generally can be used for displays, flat lamps and signage boards while the point emitter can be a suitable candidate used for x-ray sources and electron beam sources. There have been many studies on the planar typed field emitters made by CNTs3,4 but a few reports on the point typed field emitters4-7. For x-ray source or electron beam source applications of field emission, small electron spot is necessary from the CNT emitters. The point typed CNT emitters is the useful way to get a focused electron beam using a simple technique. Here, we demonstrated a fabrication method of the CNT point emitters and also investigated field emission properties from the CNT point emitters. According to our experimental results, the CNT point emitters showed high emission performance and good emission stability, which can be used for various applications. Moreover, it indicated high emission stability at a long term operation condition. Moreover, the emitted electrons were well-focused without electron spreading phenomena. We suggest that the CNT point emitter can be applicable to x-ray sources or e-beam sources.
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