Electron field emission from carbon nanotubes on porous alumina

Abstract

We have synthesized carbon nanotubes by chemical vapor deposition using ferrocene as single source organometallic precursor both on commercial (Anodisc®) and electrochemically etched porous alumina templates. Carbon nanotubes of about 20nm diameter and some μm in length appeared apart on the alumina membranes. Integral field emission measurements of these cathodes were performed in a diode configuration with luminescent screen. High emitter number densities of at least 10000∕cm2 and current densities up to 32mA∕cm2 were obtained at an electric field of 7.2V∕μm. Cathode processing at pressures in the range from 10−7to5×10−4mbar resulted in improved current stability measured over 18h. High resolution emitter distributions obtained with the field emission scanning microscope yielded up to 62000emitters∕cm2 at 23V∕μm. Single emitter investigations showed Fowler–Nordheim behavior up to 1μA and current limits up to 12μA in dc operation. Reversible switching between different emission states was also observed. Possible explanations of these phenomena and their impact for applications will be discussed.