| Carbon nanotube field emission array (CNT FEA) has rapidly evolved into a research field since the discovery of carbon nanotube in 1991. Due to carbon nanotube having a high ratio in length-radius, low work function, excellent electrical conductivity and stable chemical property and unique mechanics characteristics, it may realize the high field emission current density in theoretically. The electron emission source based on nanotube can be widely used in microwave power application, field emission monitor, components of X-ray tube.In this paper, firstly, a detailed analysis of carbon nanotube field emission properties and the influencing factors of field emission have been done. Then we have conducted the exploring research to the carbon nanotube field emission array's preparation. The experiment results indicated: As an essential material in microwave plasma chemical vapor deposition (MWPCVD), the catalyst acted as the carbon source decomposition active centers as well as the graphite carbon deposition center to product's appearance and the structure. The catalyst simultaneously is also the nucleation center and transport during carbon nanotube growing, its selection, the preparation, as well as the carrier selection is very important for carbon nanotubes'coring, its growth rate, density, separation, purification and so on. Two kinds of catalyst layers preparation methods based on predecessor's foundation was summarized. The mask photo-etching technology for producing catalyst layers structure have made some experimental analysis, such as the catalyst material, catalyst layer thickness, the structure of catalyst layers, deposition rate of catalyst and some other key factors. The combined action influences of temperature and catalyst in carbon nanotube growth have been studied also. With the help of many experimental and scanning electronic microscope's charts, we have successfully prepared well-aligned and good coherence samples of carbon nanotube arrays. Prepared CNT FEA samples were carried field emission test under high vacuum system. The I-V curve of the prepared CNT FEA shows that the maximum emission current density is more than 1A/cm2 with the total emission current of 250mA. The life time test results indicated that the emission current only decayed 3% after 500 hours continuously emission.At last, the article has done simulation and optimization of the field emission structure which were based on carbon nanotubes to get better field emission performance. The carbon nanotube array optimization density has been carried on the theory contrastive analysis for two different ratios in length-radius of carbon nanotubes. The results revealed that optimized density of higher ratio in length-radius of nanotube is larger than the lower ratio in length-radius one. The analog simulation also calculated the best field emission array density of the nanotube we have used in experiments, and discovered that carbon nanotube arrays might have the maximum current density when its distance between each other is about its height 1.5 times. This simulation results have supervised the future experiments. The triode field emission structure based on carbon nanotube was becoming the research hot spot, but there was a distance to the practical application. This article has referred the commonly used gate structure and designed carbon nanotube emitter in simulation. We have analyzed its field emission performance, and the most three important parameters which were sensitive in triode structure, they are relative position between carbon nanotube and gate, gate radius and gate voltage. The computation results were described and analyzed; these theory achievements were useful for following preparation of triode structures. |
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