Research On Field Emission Characteristics Of Carbon Nanotubes And Fabrication Of Novel Emitters

This thesis has investigated several facets of carbon nanotube (CNT) field emission phenomena ranging from characteristics to applications.In the first part of the thesis, by analyzing the field emission of heated CNTs in an ultra high vacuum chamber, we have found that the field emission of intrinsic CNT follows the Fowler-Nordheim (FN) theory fairly well, and the deviation of emission characteristic from FN theory at room temperature is caused by gas adsorption and desorption occurred to CNTs. By further analyzing the field emission characteristics of CNT at different heating state, we have found that for this sample after heating in ultra high vacuum, the adsorption at lower voltage is caused by the emission field, and desorption at high voltage is caused by the Joule heating effect of emission current.In the second part, we have measured the work function of CNT yarns with thermionic emission method which is one of the key parameters for electron emission, and found that the value around 4.6eV near to that of graphite. The value measured from yarn is a mixture of sidewall and tip emission of CNT. To further distinguish them, we have measured the work function of the sidewall of multiwalled, double walled and single walled CNT bundles using a lithography micro electrode structure. We have observed multiwalled CNT has higher work function than single and double walled CNT. At the same time, we have found the experiment evidence of work function difference between the sidewalls and tips of CNTs. It seems that the work function of tips is slightly lower than the side walls.Because we have found the intrinsic field emission of CNT follows FN theory fairly well, and the work function of CNT is almost same with graphite, we can assert that the excellent field emission of CNTs is mainly caused by their unique one dimensional structure.Therefore, in the third part we focused on improving the emission abilities of CNT emitters through controlling their morphology. At first, based on the widely adopted screening printing fabrication of CNT emitters, we developed a new spraying method to fabricate CNT emitters. CNTs are all exposed on the surface of the emitter without post-treatment, which is usually necessary in conventional printing process. We have fabricated a diode emission device with this method. Another kind of conventional CNT cathode is the arrays directly grown on substrate. Because CNTs at the bottom of the grown CNT arrays are usually well aligned, we developed a bottom-up process to fabricate emitters which involved adhering of the top of CNT array to the screening printed paste, sintering and removing from substrate. The emission properties of such kind of cathode have been studied. We have developed an imprinting method to make patterned CNT arrays. The enhancement of emission has been observed, which may origin from the edge effect of imprinted patterns.We have developed a novel planar emitter structure, which is more compatible with IC processing. We at first studied the emission characteristics of a prototype of the planar emitter structure, and observed the secondary electron emission phenomena induced by field emitted electrons. Then we successfully fabricated several planar micro emitter structures, and further investigated their emission properties.