We have synthesized carbon nanotubes by chemical vapor deposition using ferrocene as single source organometallic precursor both on commercial (Anodisc (R)) and electrochemically etched porous alumina templates. Carbon nanotubes of about 20 nm diameter and some mu m 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 10 000/cm(2) and current densities up to 32 mA/cm(2) were obtained at an electric field of 7.2 V/mu m. Cathode processing at pressures in the range from 10(-7) to 5 x 10(-4) mbar resulted in improved current stability measured over, 18 h. High resolution emitter distributions obtained with the field emission scanning microscope yielded up to 62 000 emitters/cm(2) at 23 V/mu m. Single emitter investigations showed Fowler-Nordheim behavior up to 1 mu A and current limits up to 12 mu A 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. (c) 2005 American Vacuum Society.