High Rate of Hydrogen Incorporation in Vertically Aligned Carbon Nanotubes during Initial Stages of Growth Quantified by Elastic Recoil Detection

We quantified the amount of hydrogen in as-grown vertically aligned multiwall CNTs at different stages of growth using elastic recoil detection analysis (ERDA). We suggest that hydrogen is associated with atomic defects and/or amorphous carbon impurities formed at earlier deposition stages. We found that the highest amount of hydrogen (2.3 wt %) was incorporated during the initial growth stage (15-20 s). Our results show a decrease of hydrogen content with increasing deposition time and/or with decreasing growth rate, which points to dynamical self-annealing of hydrogen-saturated defects. Consequently, the decrease of hydrogen-related defects leads to a higher quality of MWCNTs, which can be easily detected by ERDA. This research provides new insight into the nanotube growth mechanism and provides a new characterization approach for quantifying hydrogen-saturated atomic defects in MWCNTs.