Fabrication And Field Emission Of CNTs/TiO₂/Ti Composite Nanostructures 2

Field emission has been applied to field emission displays, sensors, electron microscopes and so on. While the key point in techniques of these products is how to develop the field electron emission cold cathode with high efficiency, high stability, and good uniformity. Thereby, many nanomaterials, such as metal, semiconductor, carbide, oxide, nitride, carbon-based material and their composites, have been studied for fabrication of the cold cathodes, which should possess low work function, high field enhancement factor, well conductivity, high field emission current density and excellent field emission stability.This dissertation focuses on the fabrication and field emission of CNTs/TiO₂/Ti composite nanostructures based on our previous group work. And the main works and results are as following:(1) TiO₂/Ti nanotube arrays with different morphologies were electrochemically fabricated under 15 V in 0.5 wt% HF for different anodization time, respectively. Combining characterization and field emission test results for the samples, we can conclude that adjusting anodization time can control the morphology of TiO₂ nanotube arrays and further improve field emission behaviors. And when anodization time is moderate, TiO₂/Ti nanotube arrays have the best turn-on field of 4.6 V/μm and the strongest field enhancement factor of 1150.(2) Well-aligned TiO₂/Ti nanotube arrays were fabricated by anodic oxidation, and CNTs were deposited onto the TiO₂/Ti nanotube arrays for different deposition time at 650℃by chemical vapor deposition. Combining characterization and field emission test results for the samples, we can arrive at two conclusions. One is that CNTs/TiO₂/Ti composite nanostructures show the excellent field emission properties comparing with bare TiO₂/Ti nanotube array. Another is that the field emission behaviors can be affected by the growth time of CNTs. When growth time is 60 min, the turn-on field of CNTs/TiO₂/Ti composite nanostructure lowers to 1.3 V/μm, a high emission current density of 10 mA/cm² is easily gained at the electrical field of 5.6 V/μm, and the field emission stability is excellent.