Characteristics of 100 nm-Dot Array of Vertically Aligned Carbon Nanotube Field Emitters Fabricated by DC Plasma Enhanced Chemical Vapor Deposition

Vertically aligned carbon nanotube field emitters with 100 nm-dot array structure were fabricated using dc plasma enhanced chemical vapor deposition, where dot catalysts were patterned by electron beam lithography. In order to optimize the growth condition of VACNTs, the morphologies of CNTs were investigated by changing gas ratio between NH3 and C2H2 gases. It was found that morphology of CNTs changed from bamboo-like to hollow type structure by decreasing a C2H2 ratio from 25 % to less than 15%. Optical emission spectroscopy measurement was also carried out at various NH3/C2H2 gas ratios, where emissions of CH and C2 radicals increased with increasing a C2H2 gas ratio while H radicals remain almost constant. A bamboo-like CNT formation might be resulted from the excessive carbon supply at higher C2H2 gas ratios. It was found from the field emission measurements that turn-on voltages were reduced from 1.9 V/�m for bamboo-like CNTs to 1.2 V/�m for hollow type CNTs.