Preparation And Study Of Field Emission Performance Of Highly Ordered A-CNTs/TiO₂ Nanotube Arrays

In this paper, Highly ordered TiO₂ nanotubes（Titanium dioxide nanotubes, TNTs）array and amorphous carbon nanotube/TiO₂ nanotubes（Amorphous carbon nanotubes/titanium dioxide nanotubes, a-CNTs/TNTs） array with heterogeneous structure were prepared by two-step anodic oxidation method and liquid-phase electrochemical methods under high voltage, respectively. We investigated into the influence of the prepared condition, As voltage and time and so on, on the sample morphology and field electron emission performance, the study found that CNTs/TNTs array with the orderly heterostructure owed a excellent field emission properties, the mechanism of field emission enhancement of the materials were discussed.The main contents and results of this paper is as follows:1. Using two-step anodic oxidation method, highly ordered TNTs array was prepared in the mixed solution with the ethylene glycol and ammonium fluoride. The study found that the anodic oxidation voltage and time had important influence on surface morphology, size and the field emission properties of TNTs array. Under the condition of 45 V voltage and 4 h, the surface of TNTs array was smooth, uniform and without flocs, the mouth of nanotubes didn’t appear gathering and lodging phenomenon and the wall of nanotubes is smooth. TNTs array had a good field emission performance accordingly.2. Using liquid-phase electrochemical method under high voltage, the methanol used as carbon source, highly ordered a-CNTs/TNTs array with heterogeneous structure were prepared on the TNTs array of the optimized condition.the influence rules of the Voltage and time on the a-CNTs array growth are studied.Results showed that carbon nanoparticles directional grow along the orientation of TNTs wall to form the structure of a-CNTs when deposition voltage was 1200 V due to the trop-limiting carriers of TNTs array. As deposition time increased to 10 h,a-CNTs gradually closed connection, filled and even formed a layer of disordered amorphous carbon layer in the thin-film surface. Field emission test showed that a-CNTs/TNTs arrays had excellent field emission performance when depositon voltage was 1200 V and deposition time was 8 h.3. The surface topography, structure and field emission properties of TNTs array,a-CNTs/TNTs array with the heterogeneous structure and amorphous carbon film（a-C:H） were studied, respectively. Result showed that between a-CNTs and TNTsformed good interface bonding. Field emission performance of highly ordered a-CNTs/TNTs was far better than the single structure TNTs and the a-C:H. Field emission test results showed the the minimum of threshold electric field was 2.6V/μm; the maximum of emission current density was up to 14 mA/cm2 when the electric field intensity was 5.2 V/μm. The study found that the excellent field emission performance of the highly ordered heterostructure a-CNTs/TNTs array could be attributed to uniquely ordered nanostructure, excellent field emission properties of materials and designed effective multi-layered composite structure.