| Summary: | 碩士 === 國立臺灣海洋大學 === 光電科學研究所 === 104 === In this paper, characteristics of field emission and thermal-assisted field emission of carbon nanomaterials such as carbon nanotubes, graphene and micron size of graphite powders are examined. These carbon materials have layered structure with excellent electron transport properties and good mechanical strength which have their potential to become a thermal-assisted field emission electron source. Owing to the high field enhancement effect at emission site on the region of nanomaterials, we assemble these nanomaterials into vacuum electronic devices. We analyze the characteristics of these vacuum electron device on the field emission and thermal-assisted field emission effects.
We produce three different vacuum microelectronic components, and analyzed the electronic properties.
1. Commercial carbon nanotubes dissolved in an aqueous solution to produce a concentration of 20 % weight percent solution, follow the tungsten surface immersed in the solution to prepare a field emission vacuum diode comprising of carbon nanotubes.
2. By the same method for the preparation of carbon nanotube solution to prepare a concentration of 20 % weight percent solution micron sized graphite particles, soaked in a solution to get field emission diode with graphite particles as cathode.
3. Graphene samples are prepared by high-temperature furnace tube growth through solid carbon source, and then use ferric chloride copper etching to obtain graphene, finally provoked by the tungsten become a field of graphene electron source, and then the above samples were mounted on the self-assembly of a field emission device. We observe the field emission effect of each material, and analysis of features of thermal-assisted field emission. The results show that nanoscale materials have more superior field emission cathode characteristics.
In order to enhance the device characteristics, we use thermal-assisted field emission principle to operate the vacuum devices. Using carbon nanomaterials configure three micro triode vacuum tubes, with the cathode materials as described. The result shows the nanomaterial as a cathode electron source can increase the current gain of this three terminal element components and significantly enhance the on/off ration of device switching performance. When using carbon nanotubes as a cathode material can perform the maximum current gain 7.40. While graphene on the cathode material, it enable the device to achieve the highest performance of on/off ratio 774.44. Graphene must be activated by a high electric field, and repeat cycle test of voltage rising and falling times, and has reached a stable field emission current performance. This shows the graphene has excellent thermal-assisted field emission electron efficiency.
We believe that the carbon nanomaterials can produce more efficient energy electron beams. Such materials can be used in the high-resolution electron microscopy or other related applications.
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