Field emission from individual vertically carbon nanofibers

Individual high-aspect-ratio carbon nanofibers (CNFs) were grown on W wire by plasma-enhanced hot filament chemical vapor deposition method, using a gas mixture of methane and hydrogen. The average diameter and length of carbon nanofibers are 60-100 nm and 6-30 μm, respectively, and the density of carbon nanofibers is less than 106cm-2. The field emission properties from individual carbon nanofibers have been measured using a movable W probe with a low-curvature radius. The results indicated that the CNFs showed a turn-on field of about 5 V/μm and the field-emission current density of 20 μA/cm2 at 5 V/μm. The experimental data also indicated that the length of CNFs and the position of a CNF are responsible for the properties of field emission related to the parameters such as the work function of materials, applied field and the field amplification factor. Furthermore, the electron scattering induced by defects in CNFs is also a key factor on the field-emission current.