The Research Of Carbon Nanotubes Cold Cathode Ion Source

Carbon Nanotubes (CNT) has excellent electrical and mechanical properties. CNT show excellent field emission characteristics in a high vacuum environment. It is one of the ideal electron source materials. CNT cold cathode is expected to solve the high power, short life and other issues of conventional hot cathode. However, there are still many problems, like density of the carbon nanotubes, emission stability and emission uniformity, which greatly limit the application of carbon nanotubes. Improving CNT field emission properties and CNT film technology can help promote its industrial applications.We analyze metallic grid structure in cold cathode device. We use screen printing method for preparing carbon nanotubes cathode directly on the metal substrate, and make three field-emission structures to test cold cathode field emission performance.In addition, we apply a negative voltage in stainless steel electrodes to test ion source performance. The main contents are:1) We use software CST to model on field emission triode structure and imulate electric field distribution and movement of electrons.We do research on relation between electron transfer rate, field emission current and grid mesh size D. Studies show that the anode current increases as D increases first, get to a peak about 67% in the time D taken 5 d, then decreases as D increases. Optimization of grid structure can lead to high anode current and rate of electrons.This provides an important reference for CNT cathode ion source device.2) Stainless steel substrate was mechanically polished and ultrasonic cleaned by acetone. We use screen printing method to prepare carbon nanotube thin films on stainless steel substrate. We use an annealing process technology, to enhance adhesion of carbon nanotubes and the substrate.CNT cathode was baked for 3 hours in 300?.3) We designed and manufactured a field emission triode structure, two kinds of mo grids, and test CNT cathode. Test show that wheel grid's (Physical pass rate of 85%) actual electrons pass rate tend to be stable at around 60% and square hole grid's (Physical pass rate of 67%) actual electrons pass rate tend to be stable at around 55%.The CNT cathode under wheel grid shows Ethr is 1.6V/?m. The same area CNT cathode under square hole grid shows Ethr is 2.5V/?m.4) We analyze gas components with suadrupole mass spectrometer.The results show vacuum chamber is quite clean before experiment.After field emission experiment, CNT will release large numbers of H2, H2O, CO, little CH4 and other hydrocarbons gas.5)Electron current generated from field emission collide with gas in the ionization space. We test ion source by applying a negative voltage in ion collecting plate. We get a good linear curve in 10-6Pa?10-3Pa, which provides an important reference for CNT field emission's application in vacuum ionization gauge.