Carbon nanofiber bundles grown by plasma enhanced chemical vapor deposition

A bundle of carbon nanofibers (CNFs) was successfully obtained on a glass substrate through a plasma enhanced chemical vapor deposition (PECVD) process. CNFs having dimensions of 100 nm in diameter and 1 μm in length nucleated on the Ni-Cr catalysis and grew selectively in a circular area 3 μm in diameter with a number density of 50 in 1 μm². PECVD was used with mixed source gases of CH₄VH₂/He and a substrate temperature of less than 743 K which was lower than the transition temperature of glass substrate. Each CNF had a nanostructure of a stacked cup-cone shaped graphite shells with a Ni-Cr nanoparticle surmounted at the top. The field emission characteristics of the CNF bundle were also evaluated up to 3 μA at 130 V and the maximum in the current-voltage relation was converted to a Fowler-Nordheim (F-N) plot using a work function value of 5.0 eV for CNF which showed an explicit linear F-N relation. This means a CNF bundle is a candidate element for two dimensional field emitter devices.