Field emission characteristics of different surface morphologies of ZnO nanostructures formed on carbon nanotubes

The zinc oxide (ZnO) nanostructure grown onto the carbon nanotube (CNT) surface could enhance the CNT FE characteristics. However, the ZnO nanostructure morphology is an important parameter to decide the FE enhancement. This study used thermal chemical vapor deposition (TCVD) to form ZnO nanostructure onto CNT bundle surface, and adjust the distance (D) between the CNT bundle and the zinc acetate (zinc source) to control the surface morphology of ZnO nanostructures. Transmission electron microscopy (TEM) images showed that the ZnO nanostructures were grown onto the CNT bundle surface uniformly. The FE results show that the optimal D was 32 cm with a tapered shape and the thickness of ZnO nanostructures was about 50 nm, which achieved the lowest threshold electric field. In addition, the ZnO-coated CNT bundles exhibited a good FE uniformity and stable current density.