Growth of aligned carbon nanotubes by plasma-enhanced chemical vapor deposition: Optimization of growth parameters

Abstract

Direct-current plasma-enhanced chemical vapor deposition (CVD) with mixtures of acetylene and ammonia was optimized to synthesize aligned carbon nanotubes (CNTs) on Co- or Ni-covered W wires with regard to wire temperature, wire diameter, gas pressure, and sample bias. A phase diagram of CNT growth was established experimentally in this optimization process. It was revealed by transmission electron microscopy that Co-catalyzed CNTs encapsulated a Co carbide nanoparticle at their tip, disagreeing with a previous report that Co particles were located at the base of CNTs CVD grown on Co-covered Si substrates [C. Bower et al., Appl. Phys. Lett. 77, 2767 (2000)]. This leads to the conclusion that the formation mechanism of aligned CNTs depends significantly on the catalyst support material as well as the catalyst material itself. Since the sample bias strongly affected the morphology of CNTs, the selective supply of positive ions to CNT tips was possibly responsible for the alignment of growing CNTs.

Growth of Vertically Aligned Carbon Nanotubes by DCPECVD System and the Effects of C2H2 Concentration and Plasma Current on the Growth Behavior of CNTs

“…A low acetylene precursor concentration led to a low surface carbon concentration and resulted in limited CNT growth. Tanemura et al [14] reported that at high acetylene concentration, the catalyst surface could be covered or reacted with carbon forming metallic carbide. In that case, C 2 H 2 fragments showed a greater tendency to form graphite or amorphous structures rather than CNTs.…”

Interaction of Palladium Nano-Crystals with Hydrogen During PECVD Growth of Carbon Nanotubes

“…Graphite nano-tubes were grown by the PECVD technique on a 500µm thin wire of Pd, as described previously [2][3][4]. Two devices were tested, one with a large reaction chamber (about 3 liter, fig1 a), another with a large vacuum tank connected with a 0.2mm orifice to the small reaction chamber (about 0.3 liter, fig 1b).…”

“…The plasma-enhanced chemical vapor deposition (PECVD) method [4] is one of the most efficient production methods of nanotubes or their closed variants graphite nano-Fibers (GNF). The hydrocarbon gas is decomposed at the metal-surface, in the case considered in this paper Pd, leading to excess carbon forming the carbon walls and excess hydrogen gas.…”

Enhanced electrochemical activity using vertically aligned carbon nanotube electrodes grown on carbon fiber

“…Additionally, a higher electron emission was also observed in CNT grown on carbon fibers compared to CNT on Si, revealing that multiwalled carbon nanotubes (MWCNTs) on carbon fibers has a great potential for emission displays 5 . However, the growth of VACNTs on carbon fibers still has not been deeply explored [16][17][18] as observed on Si and other substrates [19][20][21] . VACNTs have some advantages when compared with the ones grown without any orientation.…”