摘要
Single-walled carbon nanotubes (SWCNTs) were synthesized on SiO 2 /Si substrates by thermal chemical vapor deposition using an Al/Fe/Mo triple layer catalyst, methane (CH 4 ) as the carbon source, and a mixture of Ar/H 2 (10% H 2 ) as the carrier gas. The effects of volume ratio of CH 4 to Ar/H 2 (10% H 2 ), pretreatment time, growth temperature, and Al underlayer thickness on SWCNT growth were studied. The pretreatment time in Ar/H 2 and Al underlayer thickness were found to be crucial for a high-yield of high-purity SWCNTs, since they both governed the size of the catalyst nanoparticles. The optimum growth conditions were found to be a pretreatment time of 20 min, growth time of 10 min, growth temperature of 900 °C, and CH 4 /Ar/H 2 flow rates of 50/900/100 sccm, with a catalyst composed of Al (2 nm)/Fe (1 nm)/Mo (0.5 nm). The SWCNTs grown under these conditions have excellent field emission characteristics with low turn-on and threshold fields of 2.4 and 4.3 V/μm, respectively, and a current density of 38.5 mA/cm 2 at 5 V/μm. © 2007 Elsevier Ltd. All rights reserved.