Vertically aligned growth of small-diameter single-walled carbon nanotubes by alcohol catalytic chemical vapor deposition with Ir catalyst

Abstract

We showed that vertically aligned single-walled carbon nanotubes (VA-SWCNTs) can be grown by alcohol chemical vapor deposition (CVD) with an Ir catalyst in a cold-wall CVD system. VA-SWCNTs were grown on SiO2/Si substrates without any buffer layers under an ethanol pressure of 1 × 10−1 Pa at 800 °C. The SWCNT length increased with increasing growth time. The VA-SWCNT thickness reached almost 5 μm for a growth time of 180 min. Raman and photoluminescence spectroscopies showed that the diameters of the grown SWCNTs were mainly between 0.8 and 1.1 nm; this is much smaller than those of VA-SWCNTs grown with Fe and Co catalysts in previous studies. X-ray photoelectron spectroscopy and X-ray absorption near-edge structure spectroscopy showed that the Ir catalyst retained the metallic state during SWCNT growth. We suggest that highly efficient suppression of aggregation, an appropriate carbon–Ir bond strength and dissociation of ethanol molecules led to the growth of vertically aligned small-diameter SWCNTs with an Ir catalyst.