Field emission from TiO₂/Ti nanotube array films modified with carbon nanotubes

Well-aligned TiO₂/Ti nanotube array films were synthesized by using anodic oxidation of titanium in 0.5-wt% HF and were modified with carbon nanotubes (CNTs) assembled by using catalyzed chemical vapor deposition (CVD) at 650 °C. The morphology and the quality of the films were assessed with field emission scanning electron microscopy and Raman spectrometry (325 nm). The field emission characteristics of such TiO₂/Ti nanostructures were investigated before and after being modified with CNTs. The results show that the TiO₂/Ti nanotube arrays possess a moderate turn-on electric field of 7.4 V/μm, a field emission current density of 2.7 mA/cm² at 23 V/μm. It is noteworthy that the turn-on field of the TiO₂/Ti nanotube arrays modified with CNTs is decreased significantly to 1.3 V/μm, and the emission current density is increased to 10 mA/cm² at 5.6 V/μm. This novel structure shows high emission efficiency as a field emitter.