Surface Modification of Aligned Carbon Nanotube Arrays for Electron Emitting Applications

Abstract

We have previously developed a simple pyrolytic method for large-scale production of aligned carbon nanotube arrays perpendicular to the substrate. These aligned carbon nanotube arrays can be transferred onto various substrates of particular interest (e.g. polymer films for organic optoelectronic devices) in either a patterned or non-patterned fashion. The well-aligned structure is important, which not only allows us to prepare aligned coaxial nanowire of carbon nanotubes sheathed with polymers by electrochemical polymerization of conducting polymers on the individual nanotubes but also enables us to develop a facile approach for modification of carbon nanotube surfaces via plasma activation, followed by chemical reactions characteristic of the plasma-induced functionalities. These surface modification methods are particularly attractive, as they allow surface characteristics of the aligned carbon nanotubes to be tuned to meet specific requirements for particular applications while their alignment structure can be largely retained. The aligned carbon nanotubes with tunable surface characteristics thus prepared are of great significance to various practical applications, especially for the use of carbon nanotubes as electron emitters in flat panel displays. Particularly, we found that hexane-plasma coating reduced the turn-on electric field E to, coupled with a concomitant increase in the emission current at a constant V; the turn-on electric field decreased from E to = 2.5 V/μm, characteristic of the pristine aligned carbon nanotubes, to E to = 1.5 V/μm with a significantly increased emission current after the treatment of n-hexane plasma at 30 W, 250 KHz and under a monomer pressure of 0.65 Torr for 2 min. In this paper, we will discuss the effects of the surface modification on the electron-emitting properties of the aligned carbon nanotubes by presenting some examples from our recent work.