Effect of hydrogen on the growth of single-walled carbon nanotubes by thermal chemical vapor deposition

Single-walled carbon nanotubes (SWCNTs) were synthesized on SiO2/Si substrates and patterned SiO2 platforms by thermal chemical vapor deposition (CVD) using methane as carbon source. The effect of hydrogen on the growth of SWCNTs was systematically investigated with different combinations of methane and hydrogen at growth temperatures 800 and 900 °C. The results show that when iron oxide nanoparticles were used as catalysts, hydrogen was required for the formation of SWCNTs at 800 °C, but it was not necessary for the formation of SWCNTs at 900 °C. The yield of SWCNTs was found to be remarkably sensitive to the hydrogen concentration in the growth environment at 900 °C, but it shows less sensitivity to hydrogen concentration at 800 °C. The highest yield of SWCNTs was achieved under the condition H2/CH4=1000/1000 Standard cubic centimeter per minute (sccm) at 900 °C. In addition, the etching effect of hydrogen on SWCNTs in thermal CVD was also investigated at 800 and 900 °C. Results show SWCNTs can be etched by hydrogen at 900 °C but retains after the hydrogen treatment at 800 °C.