Preparation Of Carbon Nanomaterials And Its Field Emission Properties

As the core of vacuum micro-electronics devices, the field emission cathode will affect the whole performance of devices directly. Therefore, obtaining field emission materials that can be used in practicality and optimizing configurations of field emission cathode became a highlight of vacuum micro-electronics devices. In the dissertation, the development of field emission materials has been reviewed and field emission theory and its application have been introduced.Nanostructured carbon-based materials have attracted a great attention due to their unique structure, exceptional mechanical and electronic properties. With their high ratio in length-radius, low work function, good electrical conductivity and nanometer tip, nanostructured carbon-based materials can emit electron long time in low voltage. So they have been considered good field-emission cathode materials. In the dissertation, researches on the carbon nanotube preparation and its filed emission, graphite nanosheet preparation and its field emission, etc., were performed.1. Graphite nanosheet in thickness about 2 nm has been prepared from commercial expandable graphite by heating in a microwave oven and dispersing in ethanol by ultrasonication.2. Field emission of graphite nanosheet has been investigated. To improve the field emission performance of as-prepared samples, annealing in N2, H2 and vacuum was carry out separately. The annealing of the as-grown samples at 400°C in vacuum has drastically improved the field emission performance. An emission current density of 1 mA/cm2 over a 0.1 cm2 area has been achieved at an electric field of 3.7 V/μm with a turn-on field of 1.7 V/μm at 0.01 mA/cm2.3. Si substrate was coated with Al buffer layer and Ni catalyst layer in sequence by a magnetic sputtering method. Then carbon nanotube films were grown on si substrate by thermal chemical vapor deposition. The structure of carbon nanotube was different with and without buffer layer. It is studied that different thickness of catalyst affects the diameters of carbon nanotubes, which increase with increment of the thickness of catalyst films. 4. Field emission of carbon nanotube was grown on the cathode of magnetron has been investigated. The emission current was measured in low voltage corresponding to a field-enhancement factor of about 1.3×10~4.