To identify the deposition conditions that can minimize the nanotube density in the nanostructured carbon films without compromising the emission properties, we carried out a systematic investigation of the effect of deposition conditions on the emission properties and the structure of the nanostructured carbon films. Catalyst-layer thickness, methane concentration, deposition time, deposition pressure, and substrate temperature were the main deposition parameters we investigated. Within the parameter range for nanoparticle-dominant growth, substrate temperature and deposition time were the two factors that had the largest effect on the variation of the turn-on field. However, catalyst-layer thickness and methane concentration turned out to be the factors allowing the minimization of nanotube density with rather small concomitant variations of the turn-on field. A 50 h test showed that the emission stability of a nanoparticle film was better than that of a multiwall nanotube film with comparable emission characteristics. The feasibility of triode fabrication was verified by the successful deposition of a nanoparticle-film cathode of about 8 mum diameter using the conventional photolithography process. (C) 2003 American Vacuum Society.