Improved Field Emission Properties of Opened Carboxylated Multiwall Carbon Nanotubes on Flexible Carbon Cloth Substrate

摘要

In this study, well-aligned and very long multiwall carbon nanotube (MWNT) thin films were first grown on flexible carbon cloth by microwave plasma enhanced chemical vapor deposition (MPECVD) and then carboxylated by HNO_3 solvent. After surface modification of HNO_3, the cap of MWNT was removed. The open-ended MWNT was characterized by transmission electron microscopy (TEM) image. The field emission (FE) behaviors of as-grown and HNO_3-modifed MWNT thin films have been investigated. The field emission measurement of carboxylated MWNTs showed that a very low threshold voltage of 1.78 V/μm was required to reach the emission current of 1 mA/cm~2. The improved field emission characteristics of carboxylated MWNTs can be attributed to the geometrical configuration of a well-aligned, high aspect ratio, open-ended nanotube. A numerical simulation based on particle-in-cell parallel computing technique has also been performed. Both experimental and simulation results indicate that the opened nanotube (after HNO_3 modification) shows larger emission current than the closed nanotube (as-grown). In summary, MWNTs grown on carbon cloth and a simple, but very effective, HNO_3-modification method, providing improved field emission properties, show great potential in the applications of flexible electron source.