Study Of The Field Ion Emission Of Carbon Nanotubes

Neutron source has an extremely wide range of applications in scientific research, medical, industrial and agricultural production, it has been attached great attention to the scientists and engineers. Field ion emission has great prospects in the small neutron tube because of the high efficiency, fast startup time, ion beam precisely controlled size and other uque advantages. Carbon nanotubes have been proved to be the most stable and reliable field electron emission materials, if carbon nanotubes can be used in the field ion emission, we can be effectively overcome the current disadvantages of the ion source based on Spindt cathode field emission that presented poor srability, short life, and easy to be breakdown. This paper established a carbon nanotube(CNT) field ion emission model, and explored the ionization ion emission mechanism and the factors that affect the ion emission of the CNT. Moreover, in order to obtain a stable field ion emission,we use the CNT micro-bundle as the basic field ion emission unit, and optimized the CNT micro-bundle array structre to call for field ion emission. Then we prepared CNT field ion emission micro-bundle arrays by a microwave plasma CVD method(MWPCVD) to study its field ion emission characteristics. The results provide theoretical and experimental data for preparation of CNT-based field ion emission neutron tubes. The main contents are listed as follows:(1) We firstly studied the preparation of carbon nanotube micro-bundle array, including the photoetching process, catalyst preparation, and microwave plasma enhanced chemistry vapor deposition growth techonics. some of the factors affecting the carbon nanotube growth, such as growth time, the catalyst(Ni, Fe), plasma position were discussed. We grew carbon nanotube array seccessfully with verticality and good adhesion to the substrate, good electrical conductivity, good uniformity, less lattice defects.(2) We designed a CNT field ion emission array structure according to ion emission requirements and basing on metal field ionization theory, and proposed a appropriate theoretical model of field ion emssion from CNT array.(3) A series of field ion emisssion of prepared carbon nanotube arrays were tested using diode structure. Hydrogen, methane, oxygen were introduced into vacuum chamber under different pressure to analyzed the effect to field ion emission. Meanwhile, we also compared the different lengths of carbon nanotubes to investigate the performance of field ion emission in the hydrogen environment. Moreover, we also examined the stability at different ion emission current at a constance anode voltage.(4) We proposed field ion emission cathode component based on a outer-gate structure. This component can effectively avoid the tinder and breakdown of traditional cone-based Spindt cathode array. And we simulated the transistor structure.(5) We prepared the field ion emisson cathode component, and welded the grid on the gate successfully, followed by a assembling of the whole component.