Morphology control of patterned carbon nanofiber arrays for field emission applications

Carbon nanofibers (CNFs), grown by dc plasma-enhanced chemical vapor deposition, have differences in morphology and resulting field emission properties depending on underlying buffer layers. We patterned 200-nm-sized Ni catalyst dots, with 2-5 μm spacing, by e-beam lithography and obtained regularly spaced vertically aligned CNF arrays. CNFs, grown on Ti-buffered Si substrates, showed a needle like shape with a high aspect ratio, but CNFs directly grown on Si substrates, had a cone like shape. The former showed a smaller turn-on field (11 V/μm) than the latter (27 V/μm), in field emission current measurements. Moreover, the maximum current density of the CNF array on Ti was as high as 10 A/cm².