Abstract Submitted to the    NANOTUBE'04 Conference:

Carbon nanotubes (CNTs) are well-suited as electron field emitters (FE) because of their high aspect ratio, sufficient conductivity and high mechanical stability. Key properties for FE applications are high emitter number densities N, stable emission currents I at low electric fields E and long cathode lifetimes. We have synthesized CNTs on porous alumina membranes (PAM) using ferrocene and related structures which provide the advantage of catalytically active metals and carbon sources in a stoichiometrically well-defined ratio. Two growth processes occur during MOCVD: (i) tubular structures within PAM and (ii) CNTs on the surface. AFM, SEM, EDX and HRTEM investigations showed that (i) are composed of pyrolytic carbon with embedded metallic nanoscale particles and (ii) leads to irregular CNTs of small diameter. Integral FE-measurements of these CNTs in a spacer-free diode configuration with luminescent screen (IMLS), CCD-camera and video-recorder suggest surface-CNTs as emiss ion sites with tubular structures as electrical base-contact. High N~10000/cm2 and I<32mA/cm2 were obtained at E<10V/µm. Long-term processing effects at pressures up to 5x10-4mbar resulted partially in degradation and activation of emitters as revealed by IMLS-images. High-resolution measurements with the field emission scanning microscope (FESM) showed Fowler-Nordheim-behavior of single emitters for I<1µA and saturation for dc I<12µA. The FE of these phenomena and their impact for applications will be discussed.