Electron field emission from the carbon-doped TiO2 nanotube arrays

The field-emission characteristics of the carbon-doped TiO2 nanotube arrays (TNAs), which can be obtained by a heat treatment of the as-fabricated TNAs under a continuous argon and acetylene flux, were investigated. The morphology, crystalline structure, and composition of the as-grown specimens were characterized by the use of field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. It was found that the samples' turn-on electric field is reduced from 21.9 to 5.0 V/μm and the field-emission current density rapidly reaches about 9.0 mA/cm2 at 11.8 V/μm after carbon doping. The dramatically improved field-emission characteristics would be mainly attributed to the reduced work function and the enhanced conductivity due to the carbon doping into TNAs.