ZnO-nanoparticle-coated carbon nanotubes demonstrating enhanced electron field-emission properties

Multiwalled carbon nanotubes (CNTs) were coated, using atomic layer deposition, with a thin layer of ZnO and subsequently annealed. Studies of the morphologies of the ZnO-coated CNTs revealed no significant change in the internal structures (multiwalled graphite sheets) and the diameters of the CNTs, but the ZnO appeared to form bead-shaped single crystalline particles attaching to the surface of the nanotubes. The electron field-emission properties of the ZnO-coated CNTs were dramatically improved over both uncoated CNTs and ZnO nanowires. It is reasoned that numerous ZnO "nanobeads" on the surface of the nanotubes serve as additional emission sites, in addition to the tips of CNTs, and result in the enhancement of electron field emission. (C) 2006 American Institute of Physics.