Precise control over physical characteristics of Carbon Nanotubes by differential variation of Argon flow rate during Chemical Vapor Deposition processing: A systematic study on growth kinetics

In this paper, we report a systematic work on growth analysis of carbon nanotubes (CNTs) using thermal CVD method where fine tuning of CNTs׳ physical characteristics, i.e. length(height of carpet), diameter, number of walls and orientation have been greatly achieved by simply varying the Argon(Ar) gas flow rate in the Ar and Acetylene gas mixture. Ar flow rate was varied from 0 to 100 sccm with 20 sccm interval and the growth evolution was monitored by FESEM, HRTEM, and Raman spectrometer. A gradual change was observed in the reduction of diameter, increase in height, decrease in defect density, and change in orientation from horizontal to vertical of the CNTs grown over the prescribed flow rate range. Growth mechanism is discussed at every step of Ar flow rate in consideration of the analysis done on the image from electron microscopes and Raman spectra.