Growth of High-Density Self-Aligned Carbon Nanotubes and Nanofibers Using Palladium Catalyst

Abstract

In this paper we demonstrate vertical self-aligned growth of carbon nanotubes (CNT) and carbon nanofibers (CNF) using 1 nm of Pd as the catalyst material. Results were compared with those obtained using traditional catalysts (Co, Fe, and Ni). Pd is of interest as it has been demonstrated to be an excellent material for electrical contact to nanotubes. CNT were grown using plasma-enhanced chemical vapor deposition (PECVD) at 450°C to 500°C and using atmospheric-pressure chemical vapor deposition (APCVD) between 450°C and 640°C. The results were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. High-density (1011 cm−2 to 1012 cm−2) self-aligned CNT growth was obtained using APCVD and Pd as the catalyst, while Co and Fe resulted in random growth. TEM revealed that the CNT grown by Pd with PECVD form large bundles of tubes, while Ni forms large-diameter CNF. It was found that the CNT grown using Pd or Ni are of low quality compared with those grown by Co and Fe.