Osmium catalyzed growth of vertically aligned and small-diameter single-walled carbon nanotubes by alcohol catalytic chemical vapor deposition

Abstract

We showed that single-walled carbon nanotubes (SWCNTs) could be grown on SiO2/Si substrates by alcohol catalytic chemical vapor deposition (CVD) with an Os catalyst in a cold-wall CVD system. At a growth temperature of 700 °C, web-like SWCNTs were grown with diameters distributed below 0.9 nm. At a growth temperature of 800 °C, the SWCNT density increased and vertically aligned SWCNTs (VA-SWCNTs) 70 nm thick were grown on the SiO2/Si substrates after growth for 30 min. Raman and transmission electron microscope results showed that the diameters of the grown SWCNTs were distributed between 0.65 and 1.0 nm, and were much smaller than those of VA-SWCNTs obtained from conventional catalysts such as Fe and Co. Furthermore, compared with Ir, which has been reported to be a suitable catalyst for growth of small-diameter SWCNTs, we showed that Os could grow SWCNTs with even smaller diameters. Additionally, neither an alumina buffer layer nor cocatalyst were necessary to grow VA-SWCNTs with the Os catalyst. We consider that highly efficient suppression of aggregation and the relatively strong carbon-Os bond strength contributed to growth of small-diameter SWCNTs from the Os catalyst. Our studies are the first to report on Os as a catalyst for SWCNT growth, leading to SWCNTs with diameters less than ~1 nm. Hence, period 6 platinum-group metals are likely to be good catalysts for highly efficient growth of small-diameter SWCNTs.