Authors: M.G. Hahm, M.A. Noah, Y. Kwon, Y.J. Jung
Affilation: Northeastern University, United States
Pages: 1 - 3
Keywords: singlewalled carbon nanotube, chemical vapor deposition, diameter control
The role of ethanol flow rate in CVD process for the diameter control of vertically aligned-SWNTs is presented. Three different flow rates of ethanol (50, 100, and 200 sccm) were supplied to grow VA-SWNTs while keeping all other CVD parameters are the same. Raman mapping technique was performed to evaluate the diameter distribution of VA-SWNTs in a laerge area. RBM spectra from such VA-SWNTs was extracted for Raman images showing the region where the specifc Raman RBM spectrum occupies. Under the lower ethanol flow rate, smaller diameters of VA-SWNTs (0.90 nm for 50 sccm) are dominant. However, the larger diameters of VA-SWNTs were formed under the higher ethanol flow rate (1.65nm for 200sccm). We also performed computational calculation to investigate the effects of ethanol flow rate on carbon kinetics on cobalt particles. Kinetics and dynamics of carbon atoms on Co catalyst particle surfaces, which play a major role in the formation of SWNTs was studied. Carbon atoms from slower flow rate, which seem to have lower mobility than those from higher flow rate, tend to form smaller diameter SWNT seed on the top of Co particles, whereas those from faster flow rate move relatively easily to form larger diameter seed.