| Due to their special geometrical morphology, excellent physical and chemical properties, carbon nanocoils (CNCs) have been considered having the potential to be excellent electron emitters. For the one hand, just the same as carbon nanotubes (CNTs) CNCs have the high ration of length to diameter, which benefits the concentration of electric filed on CNCs’tips. For the other hand, because of their unique helix morphology, CNCs can get much more electron emission sites located not only on their tips but also on the body surface, which could help to improve the strength and stability of the emission current. Moreover, due to their helix morphology, CNCs don’t bind with each other, and are easily to be dispersed in the solution. In addition, CNCs have good electric conductivity and stable chemical property. All of above mentioned make the CNC to be an important candidate of the novel electron field emission materials.Much research has been done to investigate the field emission properties of large area CNCs, but the field emission property of individual CNCs has less been reported. In order to understand the field emission property of the CNCs more deeply, we prepared individual CNC samples and tested their field emission characteristics in this work. The main contents of work are as following:(1) Fe2(SO4)3/SnCl12solution was selected as the catalyst precursor to produce CNCs using a thermal CVD method. After that, individual CNCs were obtained by micropositioner equipped on the optical microscope. The vacuum system for the field emission test of the CNCs can reach a vacuum degree of2×10-6torr. A microscope (magnification:200X) was fixed right above the view window of the vacuum chamber, using which we can in situ observe the process of the field emission. Except for high sensitivity ampere meter and high voltage power, an oscilloscope was also connected into the testing circuit to detect the rapidly changing field emission current.(2) The internal structure change of the individual CNCs during field emission was also investigated by comparing the selected area electron diffusion (SAED) patterns and Raman spectra of the CNCs before and after field emission. It was found that the SAED patterns after field emission are finer than those before emission, and the SAED rings corresponding to (002) plane turned into arc-shaped spots after field emission. It can be concluded from this phenomenon that the crystallinity of the CNC after field emission was improved. The Raman spectra also supported this conclusion. According to the fitting of the incandescent spectra from the CNC during field emission with the Plank black body radiation law, the temperature of the CNC under strong emission current is very high, which is considered to be the main factor for the CNC internal structure improvement.(3) On the purpose of improving the field emission property of the single CNC, the single CNC’s tip morphology was modified by using laser irradiation. The CNC after laser treatment show a lower turn-on voltage and a stronger field enhancement factor. It is found that the curvature radius of the modified CNC tip becomes smaller compared with the initial one, which is the main factor contributing to the enhancement of CNC’s field-emission properties.(4) During field emission test, CNCs’self-excited vibration was observed. In this paper we have set up a simple model to analyze the force on the CNC and the vibration of the CNC. |
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