Simultaneous in situ Raman monitoring of the solid and gas phases during the formation and growth of carbon nanostructures inside a cold wall CCVD reactor

This manuscript reports for the first time, to the best of the authors' knowledge, the in situ and non-invasive characterization of both solid and gaseous phases involved in a catalytic chemical vapor deposition (CCVD) process applied with the aim to grow carbon nanotubes (CNTs). The here reported characterization comprises the simultaneous in situ analysis of carbon nanostructure formation and growth, the deactivation of the catalyst as well as the in situ monitoring of the carbon source conversion and the accompanying thermal effects in the gas phase. Raman spectroscopy is used as in situ measurement technique and after the CCVD process, as ex situ measurement tool aiming to confirm the in situ measurements performed at harsh conditions inside the reactor (temperatures up to 1000 K). The in situ Raman results have also been compared with post-CCVD SEM and TEM analysis, from which the ambiguous meaning of the D/G-ratio was extracted.