Emission from carbon nanotubes etched by a dc plasma

Abstract

This study investigates the effect of NH3 gas upon the growth of carbon nanotubes (CNTs) using thermal chemical vapor deposition. It is considered that the CNT synthesis is thought to occur mainly through two steps, clustering of catalyst particles followed by growth of CNTs. We, thus, introduced NH3 during either an annealing or growth step. When NH3 was fed only during annealing, CNTs grew longer and were more highly crystalline with their diameters unchanged. Addition of NH3 during growth, however, resulted in shorter CNTs with lower crystallinity and increased diameters. Vertically aligned, highly populated CNT samples showed poor field emission characteristics, leading us to apply post-treatment onto the CNT surface. The CNTs were etched back by dc plasma of N-2 to reduce the population density and the radius of curvatures of CNTs, which resulted in a considerable improvement of the field emission characteristics.