Field Emission Properties Of Carbon-doped TiO₂Nanotube Arrays With Controllable Doping Content

Well-aligned TiO₂/Ti nanotube arrays, possessing low work function （4.5eV）,high aspect ratio, and small curvature radius, can be easily synthesized in low cost.And they are considered to be promising cold cathode emitters. However, it is foundthat, as the field emitters, the TiO₂/Ti nanotube arrays still face some challengesincluding of high turn-on field, low emission current, and so on. Relevant researchesindicate that carbon doping into TiO₂/Ti nanotube arrays can introduce the dopinglevels, raise their Fermi level, and enhance the field emission properties. In addition,adjusting the content of carbon and the reaction temperature is a facile approach tounderstand and to optimize the field emission properties of the carbon-doped TiO₂nanotube array emitters. Therefore, based on previous works of our group, this thesisfocuses on field emission property of carbon-doped TiO₂nanotube arrays withcontrollable doping content. And the main works and results are shown as following:1. Well-aligned TiO₂/Ti nanotube arrays are synthesized by anodic oxidation anddoped with carbon by pyrolysis of C2H2at550°C. With controlling doping content ofcarbon, the field emission properties of carbon-doped TiO₂nanotube arrays aresuccessfully optimized. And the morphology, crystalline structure, and composition ofthe as-grown specimens were characterized by using of scanning electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy, respectively. It is found thatcarbon doping does not change the surface morphology of the TiO₂nanotube arrays;instead, it improves the concentration of the electron, raises the Fermi level, andreduces the work function, resulting in enhanced field emission performances. Moresignificantly, the field emission properties of carbon-doped TiO₂nanotube arrays canbe optimizes by adjusting the carbon content. When the carbon content are0.62,0.82,1.81, and3.31at.%, the turn-on fields are11.60,6.35,4.10, and5.77V/μm, and thecorresponding threshold fields are19.1,14.4,6.7,13.9V/μm, respectively. Theoptimal emitters are obtained when carbon doping content reach to about1.81at.%.2. Well-aligned TiO₂/Ti nanotube arrays are synthesized by anodic oxidation andtreated with carbon by pyrolysis of C2H2at750°C. The results indicate that TiO₂/Ti nanotube arrays retain their tubular structures after carbon treatment. However, theroughnesses of surface of sample are increased, and the TiOxCy phase is appeared.Coupling with the enhanced conductivity and up-shifted Fermi level, thefield-emission characteristics of TiO₂/Ti nanotube arrays are significantly improved,for example, the turn-on field can be decreased to1.6V/μm, and the threshold field is6.2V/μm.